Scoria Cones As Climate and Erosion Markers: Morphometric Analysis of Erebus Volcanic Province, Antarctica, Using High-Resolution Digital Elevation Data

Scoria cones as climate and erosion markers: morphometric analysis of Erebus Volcanic Province, Antarctica, using high-resolution digital elevation data

THESIS

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University

Andrew L. Collins

Graduate Program in Earth Sciences

The Ohio State University

2015

Master's Examination Committee:

Professor Terry Wilson, Advisor

Professor Michael Durand

Professor Ian Howat

Andrew L. Collins

2015

Abstract

Cinder cones in the Erebus Volcanic Province provide important markers of climate, erosion, and stress in the Ross Sea region of Antarctica, but they have not previously been systematically studied. Cinder cones provide ideal subjects for morphological analysis because they consistently form as radially symmetric landforms with approximately constant slopes. DEMs are used in tandem with satellite images and parameterization algorithms in this study to characterize landforms and surface properties of glaciated and non-glaciated Erebus Volcanic Province cinder cones.

Cone dimensions are similar to those in other intraplate environments and generally smaller than cones in subduction- and rift-related settings. Average height/width ratios are more characteristic of volcano cone fields than platform cone fields, but the volcanic terrain of the Erebus Volcanic Province is likely a complex combination of both field types. Elongation of cinder cones in the Erebus Volcanic

Province is common and most elongated cones have long axes oriented parallel or subparallel to the slope direction of terrain underlying them, indicating topographic control of cone asymmetry. Some cones with orientations independent of terrain controls suggest that regional stresses exert control on cone elongation, as suggested by previous research. Shape modification by wind and overriding glaciers may also play a role in producing cone asymmetry.

Erosion rates on cinder cones in the Erebus Volcanic Province are generally slower and more linear than in other, more temperate regions. This is most likely due to a decreased influence of the role of liquid water, as evidenced by lack of increasing surface irregularity with time. Previous research has shown that wind has significant abrading power when persistent, and that volcanic terrain has increased shear strength because of surface roughness and angularity. Both of these factors likely contribute to the relatively slow rate of erosion in the EVP compared with fields in the southwestern US, the Canary

Islands, Mexico, and Russia.

The role of cold-based glaciers in polar erosion regimes was evaluated for the

Pleistocene and remains unclear. Rates of slope degradation for glaciated and non- glaciated cones are similar, and statistical analysis indicates that the trends are statistically indistinguishable from one another. Therefore it may be that overriding by cold-based glaciers does not markedly affect cone morphology. Surface irregularity does increase after repeated overriding by polar glaciers compared with glacier-free cones.

This might be linked to meltwater channel activity at the base of polar glaciers during times of glacial cover.

Morphologic study of cinder cones has established an age-calibrated rate of surface change in a polar desert environment. Establishment of an absolute age classification based on the degree of cone slope and height/width degradation can potentially be used to assign ages to the hundreds of undated cones in Antarctica, and may also prove applicable as a dating tool for volcanism in other cold-desert environments, such as those on Mars and other terrestrial planets. Because of error ranges

iii in parameters and age values, absolute age can currently only be assigned to broad age groups with a reasonable degree of certainty. However, a more comprehensive understanding of the factors that affect initial cone formation and morphological change over time may allow better constraints for more precisely predicting cinder cone age.

Dedication

This document is dedicated to my family and friends.

Acknowledgments

I would like to extend my thanks to my advisor, Dr. Terry Wilson, for her help and support, and for providing me with the opportunity to do research in this spectacular and unique environment. I am extremely grateful to Claire Porter and the team at PGC for curating and providing stereo satellite imagery, without which this project would have been impossible. Many thanks to Dr. MJ Noh for his patience in helping me resolve the various errors I committed while learning to use the SETSM DEM algorithm, and to

Pablo Grosse and Leonardo Euillades at Instituto CEDIAC for their constant willingness to help and work with me to ensure that MORVOLC was compatible with polar projections. I would also like to express my gratitude to my thesis committee members,

Drs. Ian Howat and Mike Durand for their valuable time, input, and assistance with statistical methods.

Thanks to my friends and family for their constant support and encouragement, and to the Wilson group—the experience wouldn’t have been quite the same if I had been the only person in the office in the wee hours of the morning. This work was supported in part by an allocation of computing time from the Ohio Supercomputer Center under grant

PAS1041 to Terry Wilson. Field observations were performed and imagery and software were acquired with the support of the ANET project and NSF Division of Polar Programs award PLR-1249631 to Terry Wilson.

Vita

2008...... North Yarmouth Academy

2012...... B.A. Geology, the College of Wooster

2012 to 2013 ...... Graduate Fellow, The Ohio State University

2013 to 2014 ...... Graduate Teaching Associate, School of

Earth Sciences, The Ohio State University

2013 to present ...... Graduate Research Assistant, Byrd Polar

and Climate Research Center and School of

Earth Science, The Ohio State University

Fields of Study

Major Field: Earth Sciences

vii

Table of Contents

Abstract ...... ii

Dedication ...... v

Acknowledgments...... vi

Vita ...... vii

List of Tables ...... xi

List of Figures ...... xii

Chapter 1: Introduction ...... 1

Chapter 2: Background ...... 4

Geologic Setting of the Erebus Volcanic Province ...... 4

Tectonic setting...... 4

Geology of Erebus Volcanic Province ...... 8

Glacial history of the southern McMurdo Sound region ...... 21

Using Scoria Cones as Geomorphic Markers ...... 28

The Glacial Erosion Debate ...... 33

Chapter 3: Methods ...... 38

Morphometric and Age Analysis of Scoria Cones ...... 38

viii

DEM Construction ...... 41

Morphometric Parameterization ...... 44

Evaluating Cinder Cone Degradation ...... 60

Determining Trends in Morphologic Change ...... 60

Comparison with Previous Studies ...... 61

Chapter 4: Results ...... 65

Syn-eruptive Cone Morphology ...... 65

Cone dimensions...... 65

Ellipticity and orientation ...... 70

Scoria Cone Morphometric Evolution in the EVP ...... 77

Morphometric Parameters of Glaciated and Non-Glaciated Cones ...... 86

Accuracy of DEMs and algorithms ...... 92

Chapter 5: Discussion and Conclusions ...... 100

Cinder Cone Eruptive Variability ...... 100

Variation in cone dimensions ...... 101

Initial slope variability ...... 105

Ellipticity ...... 112

Comparison of EVP Cone Degradation with Cinder Cone Erosion in Non-Polar

Localities ...... 118

The Effect of Cold-Based Glaciation on Cone Morphology ...... 128

Cone Morphology as an Age Indicator in Polar Environments ...... 134

Summary ...... 142

References ...... 146

Appendix A: Compiled EVP Age Data and Date Source Map ...... 164

Appendix B: MORVOLC and NETVOLC Parameters ...... 175

Appendix C: Morphometric Parameters ...... 178

Key to Morphometric Parameters ...... 178

Morphometric Parameters ...... 180

List of Tables

Table 1. List of morphometric parameters ...... 53

Table 2. List of cinder cone morphology studies used for comparison ...... 62

Table 3. Average parameter values for cones based on groupings by cone age ...... 78

Table 4. Input dimensions in pixel units ...... 94

Table 5. Comparison of key parameters ...... 96

Table 6. Cone dimensions for previously studied cone fields ...... 102

Table 7. Compilation of cinder cone morphological parameters ...... 119

Table 8. Morphological parameters and statistics for grouped cones ...... 136

List of Figures

Figure 1. Map of the Erebus Volcanic Province ...... 5

Figure 2. Gondwana tight fit reconstruction and breakup model ...... 7

Figure 3. Tectonic overview of the Ross Sea ...... 8

Figure 4. LIMA satellite image of the EVP ...... 11

Figure 5. Location of the three volcanic provinces comprising the McMurdo Volcanic

Group ...... 12

Figure 6. Schematic maps showing the radial distribution of volcanic vents about Mts.

Erebus and Discovery ...... 13

Figure 7. A stratigraphic column from the ANDRILL AND-1B core with interpreted glacial thermal conditions ...... 22

Figure 8. Flowlines and surface contours of the grounded ice sheet at the LGM ...... 27

Figure 9. A photograph of Merriam Crater in the San Francisco Volcanic Field ...... 28

Figure 10. A schematic illustration showing cinder cone morphology ...... 29

Figure 11. A schematic indicating fissure eruption patterns ...... 31

Figure 12. A plot showing radial-profile evolution of a cinder cone ...... 32

Figure 13. A sequence for cold-based glacier entrainment of boulders and other debris . 36

Figure 14. A map of the EVP showing the distribution of dated flow samples ...... 40

Figure 15. A screenshot of the job status interface ...... 42

Figure 16. An illustration showing a SETSM-generated DEM ...... 44 xii

Figure 17. A DEM of an idealized volcanic cone ...... 46

Figure 18. A clipped DEM of Mount Morning draped on orthoimagery ...... 47

Figure 19. A schematic diagram showing the intersection of the z (height) axis and the cinder cone surface ...... 48

Figure 20. NETVOLC intermediary outputs for cone CC018 ...... 50

Figure 21. A DEM swatch of Cape Crozier ...... 52

Figure 22. MORVOLC output figures from cone CC018 ...... 56

Figure 23. Profile of an example cone ...... 57

Figure 24. A plot illustrating the artificial intensity of decay constants derived from short time scales and extrapolated (dashed lines) over long ones ...... 63

Figure 25. Average degradation of cinder cones in the Cima Volcanic Field ...... 63

Figure 26. Equal-interval frequency distribution of cone heights in the EVP ...... 66

Figure 27. An overview map of the Erebus Volcanic Province showing the geographic, temporal, and height distribution of cones ...... 67

Figure 28. An overview map of the Erebus Volcanic Province showing the geographic, temporal, and width distribution of cones...... 69

Figure 29. Equal-interval frequency distribution of cone widths in the EVP ...... 70

Figure 30. Equal-interval frequency distribution of cone ellipticity index values ...... 71

Figure 31. A schematic diagram showing the ideal outlines of a circle (ei = 1.00), the minimum ei value measured in this study (ei = 1.10), the threshold for designation as

‘elongated’ (ei = 1.20), the average ei of elongated cones (ei = 1.47), and the maximum ei measured in this study (ei = 2.05) ...... 72

xiii

Figure 32. Frequency distribution of cone ellipticity index values ...... 73

Figure 33. Frequency distribution of 26 elongated cones according to orientation ...... 74

Figure 34. An overview map showing the age and orientation of elongated cones ...... 76

Figure 35. Plots showing the distribution of mean total cone slope versus cone age ...... 79

Figure 36. A plot showing the distribution of mean flank slope versus cone age ...... 80

Figure 37. Variation of mean cone summit slope with age ...... 81

Figure 38. Plots showing cone height to basal width ratio versus age ...... 83

Figure 39. A plot showing the distribution of irregularity index of cones over time ...... 85

Figure 40. A plot showing the ratio of summit width to basal width of cones versus age 86

Figure 41. Glacial flow line map of ice during the LGM from Denton and Hughes (2000) overlying a map of the EVP with locations of studied cones ...... 87

Figure 42. Plots showing the distribution of height to basal width ratios of Pleistocene glaciated and non-glaciated cones ...... 88

Figure 43. Plots showing the distribution of mean total slope of Pleistocene glaciated and non-glaciated cones ...... 90

Figure 44. Plot showing trends fitted to mean slope values taking into account error in both age and slope ...... 92

Figure 45. MORVOLC-derived cone boundary delimitations from SETSM (left) and

LiDAR (right) of cone WI_013 ...... 98

Figure 46. Plots showing slope values and accompanying frequency histograms derived by MORVOLC from SETSM (left) and LiDAR (right) for cone WI_013 ...... 99

Figure 47. H vs. WB plot for compiled cone field data ...... 102

xiv

Figure 48. Combined relative frequency distributions of cone basal diameter, and cone height...... 104

Figure 49. A schematic illustration of an asymmetric cone ...... 111

Figure 50. Satellite image showing horizontal maximum (SH) and minimum (Sh) compressive stress directions relative to major structural and volcanic features ...... 113

Figure 51. A schematic illustrating the pattern of fissures around a summit caldera in a differential stress field ...... 114

Figure 52. Streamlines of prevailing wind around Ross Island ...... 115

Figure 53. Map of the EVP overlain by the LGM ice flow and extent map by Denton and

Hughes (2000) showing the age and elongation direction of cones ...... 117

Figure 54. A plot showing the H/WB degradation curves of the Erebus Volcanic Province and comparable cinder cone volcanic fields ...... 121

Figure 55. A plot showing the slope degradation curves of the Erebus Volcanic Province and comparable cinder cone volcanic fields ...... 122

Figure 56. A reconnaissance map of the Dry Valleys and EVP showing permafrost distribution by form ...... 126

Figure 57. Reconstructed pathways for ice into the Ross Sea ...... 130

Figure 58. A diagrammatic representation of the character of two different cold-based glacier flow velocity profiles ...... 133

Figure 59. A plot showing the trend of irregularity index relative to age of cones ...... 134

Figure 60. A schematic illustration showing cinder cone morphology ...... 135

Figure 61. A plot of age-averaged STOT values versus cone age ...... 137

Figure 62. A plot of age group-averaged cone H/WB values versus age ...... 139

Figure 63. A plot showing, side-by-side, the trends and distributions of both individually plotted and age group-averaged H/WB and STOT values versus cones age ...... 140

Figure 64. An orthophoto, slope map, and profiles of a volcanic feature in Taylor Valley that shows possible remnants of cone and crater morphology ...... 142

Figure 65. Map of the EVP showing the locations of compiled dates and whether they were derived from flow samples or cones ...... 174

Figure 66. EVP map showing cone locations, age, and ID labels ...... 182

xvi

Chapter 1: Introduction

Monitoring landscape change over time is integral to an understanding of Earth surface processes as they pertain both to society and to the natural world. Rivers and glaciers are dominant agents of erosion and much research is aimed at determining the rates of fluvial and glacial erosion, and how these relate to tectonic and climate drivers of landscape change (e.g. Koppes and Montgomery, 2009). Yet, erosion rates and their controlling factors have not been extensively studied in polar regimes and there is little data describing them. Unlike the subpolar (or polythermal) glaciers that effectively flattened enormous tracts of North America and Asia during the Last Glacial Maximum, polar glaciers, or cold-based glaciers frozen to their bed, are generally considered to be ineffective agents of erosion. In the Ross Sea region of Antarctica, it has been suggested that mountain landscapes have been preserved with little change over nearly 14 million years in the prevailing polar desert environment (e.g. Sugden and Denton, 2004). Some authors, however, have proposed that polar glaciers do affect morphological change over time (e.g. Cuffey et al., 2000; Lloyd Davies et al., 2009; Atkins, 2013). In temperate areas where the surface is constantly being recycled, this assertion is difficult to study, but Antarctica and its landforms provide a useful environment in which to analyze features subjected to polar glaciation.

Cinder cones are ideal tools for analysis of erosion and landscape evolution because cones typically form as simple, radially symmetric landforms with 1 approximately constant slopes (Wood, 1980). Many studies have shown that there is a systematic change in scoria cone morphology over time. For example, the slope of cone flanks decreases in a predictable manner dependent upon environmental factors that control sediment flux (Inbar et al., 2011; Pelletier and Cline, 2007; Hooper and Sheridan,

1998). Empirical and modeling studies have identified a range of parameters, including surface slope, rugosity (surface roughness), slope direction, cone height, and base diameter that can be used to quantify morphologic change (Parrot, 2007a,b; Grosse et al.,

2012). Where age dates for the cones are available, rates of change can be derived based on these parameters. In arid to semi-arid regions, chronologically-calibrated morphologic change has been used to assign ages to undated cones (e.g. Dohrenwend, 1987), but little work has been done to this end in other settings.

In a polar desert environment, dry-based glaciers and wind are primary forces driving morphologic change. Surface raindrop impact, running water, and related agents are conspicuously absent. The Erebus Volcanic Province in Antarctica provides an optimal environment for studying morphologic change because there are abundant cinder cones spanning a wide range of ages and the cones are largely unaffected by factors that often inhibit useful data collection, such as vegetation and anthropogenic effects.

In addition to useful indicators of morphologic change, cones are also important markers of magma flux and tectonic control on magmatism. Cone height and shape irregularity are indicators of pre-eruption surface characteristics, eruption volume, and syn-eruptive processes such as vent migration due to outflow and breaching (Hasenaka and Carmichael, 1985; Kereszturi et al., 2012). Morphologic parameters such as the

2 ellipticity of the cone base and/or crater (ratio of long to short axis), the maximum/minimum cone rim heights, the directions of cone breaching, and cone elongation and alignments, are all proxies for maximum and minimum stress directions and thus important indicators of tectonic regime and stress control on magmatism

(Tibaldi, 1995; Paulsen and Wilson, 2010).

The wide geographic extent of the Erebus Volcanic Province and the logistical challenges of working in Antarctica are a hindrance to field work. Remote investigation is made possible by high-resolution digital elevation data from LiDAR and WorldView stereo satellite imagery that provide accurate and precise information on volcano morphology. Algorithms developed by previous authors and modified to suit the needs of this project are utilized in this study of the Erebus Volcanic Province. A SETSM digital elevation model extraction algorithm developed by Noh and Howat (2015) is used to construct DEMs from stereo satellite imagery. MORVOLC (Grosse et al., 2012) and

NETVOLC (Euillades et al., 2013) are employed with the DEMs to perform consistent, quantitative morphological analysis on cinder cones to assess the following key hypotheses: a) cone morphology shows a slow, but systematic change with time in a polar desert environment characterized by a lack of running water and where dry-based glaciers are a primary agent of erosion; b) cones express morphologic changes due to polar glaciation; and c) the age of cinder cones in a polar desert can be predicted based on slope degradation or other morphologic indicators.

Chapter 2: Background

Geologic Setting of the Erebus Volcanic Province

Tectonic setting

The Erebus Volcanic Province (EVP) is situated on the western margin of the

Ross Sea in Victoria Land. The EVP includes Ross Island and its three major volcanic centers (Mts. Erebus, Terror, and Bird), Minna Bluff, Mt. Discovery, and Mt. Morning to the south, and distributed volcanic vents in the Trans-Antarctic Mountains (TAM) and

Dry Valleys to the west (Figure 1).

The TAM are a rift shoulder mountain belt built upon an early Paleozoic to late

Precambrian metamorphic-plutonic complex overlain unconformably by sedimentary strata of the Devonian to Jurassic Beacon Supergroup. These strata are intruded and covered by tholeiitic sills, dikes, and associated alkaline lava flows of the Jurassic-aged

Ferrar Group, which indicate the onset of rifting associated with Gondwana (Elliot, 1992;

Wilson, 1993; Fitzgerald, 2002; Figure 2).

Uplift of the TAM initiated in pulses in the Early through Late Cretaceous, followed by major, whole-range uplift beginning approximately 55 Ma and continuing through the early Cenozoic (Fitzgerald, 2002; Fielding et al., 2006; Figure 2C). Rates of uplift in the past 50 million years averaged 100 m/Ma along the axis of greatest uplift in southern Victoria Land (Gleadow and Fitzgerald, 1987).

Figure 1. Map of the Erebus Volcanic Province (modified from Kyle, 1990a, Figure A.III.1)

The Victoria Land Basin (VLB), which sits east of the TAM in the Ross Sea and extends from north of Mt. Melbourne to south of Mt. Erebus, comprises the western end of the West Antarctic Rift System (WARS) in the Ross Embayment. The WARS spans the continent from northern Victoria Land to the Antarctic Peninsula and Weddell Sea

(inset, Figure 3). The main phases of crustal extension and thinning across the WARS occurred in the late Cretaceous, approximately 105-85 Ma, and were associated with the separation of Australia, New Zealand, and Antarctica (Lawver and Gahagan, 1994;

Fitzgerald, 2002) during the breakup of Gondwana. Basin formation and rifting in the

VLB commenced during episodes of Jurassic tholeiitic magmatism and subsidence

(Fitzgerald, 2002); however, correlated core and seismic reflection data indicate that the main phase of rifting in the VLB took place in the Oligocene between 29 and 24 Ma, and was followed by a period of thermal subsidence in the Early Miocene (Fielding et al.,

2006).

Crustal thickness varies up to 20 km between the VLB and the TAM, from approximately 19-20 km under Ross Island to 36-40 km under the TAM ~85 km inland

(Bannister et al., 2003; Hansen et al., 2009), due to normal faulting associated with crustal extension in the VLB (Fitzgerald et al., 1986).

Continued rifting during the Cenozoic was largely spatially limited to the western

Ross Sea in the VLB (Figure 3). Within the Neogene Terror Rift, a ~70 km wide N-S trending rift zone spanning the distance between the active Mt. Melbourne and Mt.

Erebus volcanoes (Cooper et al., 1987; Fielding et al., 2006; Hall et al., 2007). Seismic and drill core data indicate that the series of sub-basins comprising the Terror Rift accommodate up to 15 km of extension (Hall et al., 2007; Henrys et al., 2007). The intensity of volcanism increases southward along the rift (Cooper et al., 1987).

Figure 2. Gondwana tight fit reconstruction and breakup model showing the relative positioning of East and components of West Antarctica through the Jurassic and Early Cretaceous. Abbreviations: AP, Antarctic Peninsula; TI, Thurston Island; MBL, Marie Byrd Land; CR, Chatham Rise; CP, Campbell Plateau; SNZ, southern New Zealand; NNZ, northern New Zealand; LHR, Lord Howe Rise; WS, Weddell Sea (from Fitzgerald, 2002, Figure 1)

Figure 3. Tectonic overview of the Ross Sea showing locations of the TAM, VLB, and Terror Rift. Inset shows the context of the area within the West Antarctic Rift System. Red signifies Cenozoic volcanic rocks (modified from Hall et al., 2007, Figure 1)

Geology of Erebus Volcanic Province

Volcanic activity in the McMurdo Volcanic Group (MVG) commenced in the

Eocene, approximately 50 Ma (Rocchi et al., 2002). There is some debate as to whether volcanic activity in the MVG was rifting- or hotspot-induced (Kyle, 1990a, e.g.

Fitzgerald et al., 1986; Rocchi et al., 2002, 2003; Watson et al., 2006; Hansen et al.,

2009); the geographic configuration of the volcanoes suggests mantle plume doming

(Kyle, 1990a), earthquake seismology points to thin crust above a low-velocity zone in the mantle (Watson et al., 2006; Finotello et al., 2011), and Kyle (1990a) and Rilling

(2009) have proposed that both mantle plumes and rift-related decompression melting contributed to volcanism in the MVG.

The MVG is made up of three geographically distinct provinces (Figure 5). From north to south, these are: the Hallett Volcanic Province (HVP), the Melbourne Volcanic

Province (MVP), and the Erebus Volcanic Province (EVP). The HVP and EVP are dominated by alkaline lavas, shield volcanoes, and profuse distributed vents (Wright-

Grassham, 1987). The major volcanic centers in the HVP lie along the eastern front of the

TAM range, while those in the EVP are distributed across the range and offshore within the VLB and Terror Rift. The MVP is comprised of stratovolcanoes and vent fields, and its major centers lie within the TAM rather than on the eastern front (Wright-Grassham,

1987; Kyle, 1990b).

The EVP, which is the focus of this study, is located at the southern end of the

Victoria Land Basin, along the southwestern Ross Sea where it meets the Ross Ice Shelf, and is the southernmost of the three volcanic provinces that comprise the MVG. It falls between 77°S and 79°S latitude and between 162°E and 168°E longitude. Volcanic activity in the EVP commenced in the Oligocene, at the tail end of the main phase of

VLB rifting and during the onset of thermal subsidence (Schmidt-Thomé et al., 1986;

Fielding et al., 2006). The EVP contains five major volcanic centers at Mt. Erebus, Mt.

Bird, Mt. Terror, Mt. Discovery, and Mt. Morning, and abundant minor vent and cone fields (Figure 4). Minor centers included in this study are located at Hut Point Peninsula,

Brown Peninsula, Black Island, White Island, Minna Bluff, Mason Spur, the Royal

Society Range, and Taylor and Wright Valleys (contained within the McMurdo Dry

Valleys). Mt. Erebus is the only center still active in the province. The oldest activity expressed in the sediment record occurred approximately 25 Ma and is found in

40Ar/39Ar-dated tephra from the Cape Roberts cores (McIntosh, 2000). The oldest known outcrop samples from Gandalf Ridge on Mt. Morning have been K-Ar dated to approximately 18 Ma (Kyle and Muncy, 1989; Martin et al., 2010).

Figure 4. LIMA satellite image of the EVP showing major (bold) and minor eruptive centers with all mapped cones (pink circles)

Figure 5. Location of the three volcanic provinces comprising the McMurdo Volcanic Group, with outcrops shaded black (modified from Wright-Grassham, 1987, Figure 2.2)

The majority of volcanic vents and cones in the EVP sit on thinned crust within the Ross Embayment and their arrangements around major centers have been suggested 12 to resemble expressions of lineaments emanating radially at 120° to each other from the major volcanoes (e.g. Kyle et al., 1992; Figure 6). Together, the linear zone of major and minor volcanic centers, oriented roughly E-W at southern end of the Victoria Land Basin, has been thought to represent transfer or transform faulting terminating the Terror Rift

(Kyle, 1990a). Lineaments of cones and fissures on Mt. Morning are suggested to be related to tectonic (crustal stress) control of magmatically-induced crustal fractures during more recent (Pliocene-Pleistocene) rifting in the Terror Rift (Paulsen and Wilson,

2009).

Figure 6. Schematic maps showing the radial distribution of volcanic vents about Mts. Erebus and Discovery (modified from Kyle et al., 1992, Figure 10)

In the classification system used by Kyle et al. (1979), the composition of rocks in the EVP is dominated by three types: a fractionally crystallized basanite containing clinopyroxene, kaersutite, olivine, feldspar, and apatite; a fractionally crystallized phonolite with the addition of magnetite phenocrysts and without kaersutite; and trachyte

(Kyle et al., 1979; Kyle, 1976). Most rocks formed within the last 11 Ma (e.g. on Mts. 13

Erebus and Discovery, Hut Point Peninsula, White Island, and a few cones within Mason

Spur, the Royal Society Range, and Minna Bluff) are considered basanite-phonolite while older units (e.g. Minna Bluff, Black Island, some cones in the Royal Society Range) fall under the trachyte category. The major volcano eruptive centers are a mix of shield and composite (shield/stratovolcano) types surmounted by numerous parasitic vents, cones, and domes (Kyle, 1990a).

Ross Island

Ross Island is situated 50 km off the coast of southern Victoria Land, within the

VLB, at the boundary between the Ross Ice Shelf and the Ross Sea. Mt. Erebus, the dominant feature, is an active basanite-to-phonolite shield to stratovolcano composed of lavas erupted over the last c. 1.3 Ma (Wright-Grassham, 1987; Kyle, 1990a; Esser et al.,

2004). The lower slopes, emplaced by submarine basanitic pillow lava extrusion and subsequent subaerial low-viscosity basanitic volcanic activity from > 1.3 Ma to 1 Ma, are characteristic of mafic shield volcanism, with an average slope of approximately 9º

(Esser et al., 2004). The post-shield interval is comprised of deposits from more viscous phonolitic lavas and reaches slopes of up to 35º. The 4 km-wide summit caldera is filled and overflowed by numerous small-volume lava flows and current eruptions are characteristic of strombolian volcanism (Esser et al., 2004). Two older volcanoes and one vent zone are arranged radially around the center: Mt. Bird, a basaltic shield and the original volcano of Ross Island, at 4.6-3.8 Ma (Armstrong, 1978; Wright-Grassham,

1987); Mt. Terror, also a shield volcano with interbedded basanite flows and pyroclastic

14 breccias exposed at Cape Crozier, at 1.8-1.3 Ma (Kyle, 1976); and Hut Point Peninsula, a linear zone of volcanic cones, active from 1.3-0.4 Ma (Kyle, 1981a; Kyle 1987).

Ross Island is made of up two separate lava lineages. The peripheral volcanoes are characterized by the presence of kaersutite, whereas Erebus lacks it (Kyle, 1981b).

This difference is attributed to different degrees of fractional crystallization from a common basanitic parent magma and a higher-temperature, large central magma chamber beneath Erebus in contrast with lower-temperature, smaller, discrete magma sources for the other volcanoes (Kyle, 1981b; Moore and Kyle, 1986).

Black Island, Brown Peninsula, and White Island

These complexes are composed of primarily basaltic to trachytic coalescing volcanic vents and domes. Black Island possesses a northwesterly alignment of vents on its northern end. Though it is currently mostly ice-free, the main mass of the island is primarily covered by glacial deposits, which Wright and Kyle (1986) determined overlie a series of coalescing basaltic cones (Cole and Ewart, 1968; Wright and Kyle, 1986). The exposed volcanics on Black Island are composed of alkali basalt and phonotephrites at the older northwestern corner, and younger trachyte deposits at the southern end. Brown

Peninsula, extending north from the base of Mt. Discovery, primarily consists of coalescing, north-south aligned, basaltic volcanic centers, with the youngest activity occurring near the southern end and all but the youngest vents heavily modified by glacial erosion (Wright and Kyle, 1986).

Brown Peninsula and Black Island basalt and trachyte eruptive sequences are geochemically and morphologically similar. Geographic proximity would suggest that

White Island might be also, but it has extensive ice cover and so is difficult to compare.

The exposed portion of White Island, at the north end, is comprised of overlapping basanitic shield structures and is much younger than the south end (Cooper et al., 2007).

The oldest date (11.2 Ma) from these centers comes from the northwest part of

Black Island; the majority of Black Island ranges from 4.5-3.4 Ma (Armstrong, 1978).

Brown Peninsula ages range from 2.8-2 Ma (Wright and Kyle, 1986), while White Island ages fall within a wider range of 7.6-0.2 Ma (Cooper et al., 2007).

Minna Bluff

Minna Bluff extends 50 km southeast from the base of Mt. Discovery into the

Ross Ice Shelf. The crest of the central ridge is between 800 and 1060 m high and, though currently mostly ice-free, the volcanic exposures are partly obscured by glacial deposits. The ridge is built from a series of coalescing basanitic shields and is primarily composed of trachyte, including domes representing older phases of activity at the southeastern end, and hyaloclasite breccias and flows (Wright and Kyle, 1987a).

Phonolite domes near the northeast cape are younger, while basanitic cinder cones topping the ridge along the length of Minna Bluff represent the latest phase of activity

(Ross et al., 2012).

The timing of volcanic activity on Minna Bluff is relatively well-constrained. K-

Ar and Ar40-Ar39 dates from Minna Bluff indicate that it developed from east to west

16 beginning approximately 12 Ma (Ross et al., 2012). For the first 4 Ma, activity was centered on the Minna Hook area, migrating west and closing the gap between a proto-

Minna Bluff island and the mainland around 7-8 Ma. Significant volcanic activity continued until 4-5 Ma and volcanism continued at a more sporadic, slowed rate until c. 2

Ma. (Wright-Grassham, 1987; Ross et al., 2012). Multiple authors have suggested that the east-west axis of Minna Bluff is parallel or sub-parallel to the radial lineaments emanating from Mt. Discovery (e.g. Kyle et al., 1992; Ross et al., 2012), and Ross et al.

(2012) postulated that the north-south orientation of Minna Hook expresses the southern extension of faulting bounding the Terror Rift.

Mount Discovery

Mt. Discovery is a symmetrical stratovolcano that rises from below sea level to

2681 m. The upper slopes are composed of benmoreite flows, debris flow deposits, and volcanogenic sedimentary rocks, and capped by phonolite flows sourced from the summit cone and from parasitic domes (Wright and Kyle, 1987b). Basanite and phonotephrite flows from more recent cones extending northeast radially with respect to the summit cone comprise the surface exposures on the mid and lower slopes, with glacial deposits covering volcanic exposures at the base (Wright-Grassham, 1987).

Sparse K-Ar dates suggest that Mt. Discovery formed approximately 5.4-5.3 Ma, with parasitic vents developing on the north and east sides until as recently as 1.87 Ma near the base of the edifice (Armstrong, 1978; Wright and Kyle, 1987b; Wright-

Grassham, 1987). More recent Ar40-Ar39 analysis indicates that younger basalt flows and

17 dikes, dated at 0.06 and 0.18 Ma, respectively, are found on the apron near the base of the volcano (Tauxe et al., 2004).

Mount Morning

The volcanic sequence on Mt. Morning, a 2723 m shield volcano, was formed by two distinct episodes of volcanism. The earliest phases include a subvolcanic complex of

Miocene age, exposed at Gandalf Ridge and in Pinnacle Valley, at the northern ends

Hurricane and Riviera Ridges, respectively (Paulsen and Wilson, 2009; Martin et al.,

2010) and volcanic complexes at Mason Spur, on the south flank of Mt Morning (Wright-

Grassham, 1987; Martin et al., 2010). At Gandalf Ridge, the Miocene trachyandesite, phonolite, and tephrite flows unconformably overlie early Paleozoic Koettlitz Group basement rocks (Wright and Kyle, 1987c; Wright-Grassham, 1987; Kyle and Muncy,

1989). At Mason Spur, a basanitic to trachytic volcanic complex consists of two stratigraphically defined episodes of volcanism (Wright-Grassham, 1987). Volcanism at

Mason Spur occurred from 12.9-11.4 Ma (Wright and Kyle, 1987d; Wright-Grassham,

1987; Martin et al., 2010), then was apparently followed by a period of quiescence, with dome volcanism initiating at 6.1 Ma and dome and cinder cone volcanism continuing to

70 Ka (Wright-Grassham, 1987; Paulsen and Wilson, 2009). The volcanism at Mt.

Morning is the oldest known activity that crops out in the Erebus Volcanic Province.

Derived sediment from the Cape Roberts CRP-2/2A sediment core has been Ar40-Ar39 dated at 24.1 (Martin et al., 2010), delimiting the start of the first stage of Mount Morning volcanism.

Older volcanic complexes are intruded and unconformably overlain by Pliocene - recent basanite, phonolite, and hawaiite representative of the shield building phase associated with the main edifice (Wright and Kyle, 1987c; Paulsen and Wilson, 2009;

Martin et al., 2010). Numerous basanite cinder cones, generally aligned northeast- southwest with some subsidiary northwest-southeast alignments (Paulsen and Wilson,

2009), formed along Riviera and Hurricane Ridges during this phase (Wright-Grassham,

1987; Kyle and Muncy, 1989). The younger phase of activity has been dated continuously from 5.0 Ma to present, primarily at Riviera and Hurricane Ridges

(Armstrong, 1978; Wright-Grassham, 1987; Tauxe et al., 2004; Paulsen and Wilson,

2009; Martin et al., 2010).

Royal Society Range

The Royal Society Range (RSR) rises to over 3000 m above sea level and is cut extensively by valley glaciers. Volcanism in this area is primarily from approximately 50 scattered vents ranging in size from small scoria mounds to cinder cones up to 300 m high (Wright-Grassham, 1987). While most vents and lava flows were erupted subaerially, the RSR contains evidence, including pillow lavas and hyaloclastites, of some of the few known subaqueous or subglacial vents currently above sea level in the

EVP (Wright-Grassham, 1987). These occur at Koettlitz Glacier, Pipecleaner Glacier, and Hooper Crags. The majority of lava sourced from the RSR is basanitic, and certain areas, such as Dromedary Platform and Roaring Valley, are characterized by lava plains comprised of flows up to 10 km long and 10 m thick (Wright-Grassham, 1987; Wright

19 and Kyle, 1987e). Evidence also exists for supraglacial eruptive activity, characterized by disjointed and tilted blocks of welded material with related outcrop patterns, on

Pipecleaner Glacier, near Foster Crater, and on Heald Island (Wright, 1980).

Only a few dates from the RSR predate the Quaternary, with limited activity from

14.6-10.5 Ma and 7.2-4.2 Ma (Armstrong, 1978; Wright and Kyle, 1987e; Sugden et al.,

1999; Lawrence et al., 2009). Based on K-Ar and Ar40-Ar39 dates, the majority of activity has occurred within the last 2.9 Ma (Armstrong, 1978; Sugden et al., 1999; Tauxe et al.,

2004; Lawrence et al., 2009). Wright and Kyle (1987e) indicate that, based on the quantity of Quaternary volcanic activity, youthful cone morphologies, tephra entrainment in proximal modern glaciers, and K-Ar ages as young as 0.08 Ma, the RSR cannot be considered extinct.

The Dailey Islands, a group of five volcanic basanitic islands situated about 35 offshore from the RSR, are compositionally and chronologically similar to the basanitic

RSR lavas (Wright and Kyle, 1987e). Tauxe et al. (2004) obtained a 40Ar/39Ar age of 0.78

Ma for a dike on Juergens Island, and Del Carlo (2009) determined a similar age from a lava sample. Del Carlo et al. (2009) note that most of the edifices in the Dailey Islands mark remains of glacially overridden, heavily eroded basaltic cinder cones; however,

Juergens Island (the second westernmost island) still retains a symmetrical, conical shape.

Glacial history of the southern McMurdo Sound region

Evidence from the depositional style and age of sedimentary strata cored from areas within the EVP documents repeated cycles of ice sheet advance over the region in the Neogene (Naish et al., 2009). Scoria cones of the EVP formed within this time frame, from approximately mid-Miocene to the present (Figure 7). Fluctuating ice sheet thermal conditions have been reconstructed from strata in the ANDRILL cores for the last c. 20

Ma (McKay et al., 2009; Fielding et al., 2011; Passchier et al., 2011). These reconstructions constitute some of the best constraints on glaciation, sedimentation, and ice sheet evolution in Antarctica in the Neogene and Quaternary periods and are routinely used as calibration for glacial and climate modelling (e.g. Naish et al., 2009; Pollard and

DeConto, 2009).

Morphological evidence from the terrestrial record has been interpreted to suggest that terrestrial ice in the TAM and around the EVP has been cold-based and stable, excepting outlet glaciers and minor deviations induced by sea level change, since the mid-Miocene (Marchant et al., 1993; Sugden et al., 1995; Sugden and Denton, 2004;

Jamieson et al., 2010). These conditions followed a period of slow cooling across the early to mid-Miocene, which Sugden and Denton (2004) describe as a transition from cool-temperate to polar climate conditions, but with more moisture than present.

Figure 7. A stratigraphic column from the ANDRILL AND-1B core with interpreted glacial thermal conditions compared with periods of volcanic activity in the EVP. Dated cones used in this study are plotted as orange triangles on their corresponding volcanic center (modified from Millan, 2013, Figure 2.4)

The EVP region has experienced three different glacial regimes since the

Miocene, based on the interpretations of strata from ANDRILL cores (McKay et al.,

2009; Levy et al., 2012) and geomorphology studies (Marchant et al., 1996; Sugden and

Denton, 2004).

Polar (or cold- or dry-based) regimes are characterized by glaciers frozen to their bed with minimal surface melt and limited subglacial melt control on glacier motion.

Modern-day analogs of polar thermal conditions (WAIS, EAIS) indicate that these regimes are associated with low terrigenous sedimentation rates in the ice shelf environment and high biogenic sedimentation rates in proximal marine environments, resulting in thin massive diamictite deposits and fossiliferous and diatomaceous muds, respectively (Domack et al., 2005; McKay et al., 2008; McKay et al., 2009).

Temperate (or warm- or wet-based) glaciers, which are at pressure melting point throughout and which slide on a pressure-melt-lubricated bed, are characterized in the stratigraphic record by high terrigenous sediment rates and diluted or suppressed biogenic sedimentation rates (Powell and Domack, 2002). Seasonal iceberg rafting and abundant meltwater result in graded laminae and rhythmic bedding (Cowan et al., 1999; McKay et al., 2009).

Subpolar (or polythermal) regimes represent a middle member between polar and temperate glaciation, with varying sedimentation rates and deposits that vary in response to the amount of subglacial or surface melting (McKay et al., 2009). The terrestrial signature of subpolar and temperate glaciers includes significant topographic features like

23 cirques, moraines, fjords, benches, and on a smaller scale, meltwater channels, colluvium deposits and till sheets (e.g. Denton et al., 1993).

Seismic stratigraphy and sedimentation rates indicate that the Miocene marked a significant transition in the Ross Embayment (De Santis et al., 1995; McKay et al., 2009).

The Middle Miocene marked the transition to a cold polar regime that persisted into the early Late Miocene. This period was characterized by repeated grounded ice, negative

δO18 excursions (Miller et al., 1991), and little terrigenous sediment deposition offshore

(McKay et al., 2009). These inferred glacial conditions would have prevailed as the oldest volcanic terrain of this study was developing at Gandalf Ridge, Mason Spur, Black

Island, and the RSR. Onshore, sand wedges, preserved ventifact pavements, and minimal colluvium deposits, all temporally constrained isotopically using in-situ ash, also indicate a polar regime (Marchant et al., 1993; Sugden and Denton, 2004). Some scouring is noted on the coastal flanks of the mountains, signifying thicker or faster warm-based ice nearer to the coast during this time (Sugden and Denton, 2004). McKay et al. (2009) state that evidence of subglacial erosion is “generally lacking”, although not absent, in the corresponding early Late Miocene sequences in the AND-1B core.

In the latest Miocene (beginning approximately 5.5 Ma; Levy et al., 2012), there was a dramatic shift to a dynamic polythermal glacial regime near the coast, which carried into the Pliocene. This transition saw average sea surface temperatures in

McMurdo Sound rise to 3-4°C and sea level high enough to form fjords in the glacially carved Dry Valleys with bottom water temperatures between -2 and 5°C by the mid-

Pliocene (Webb, 1974; Webb and Wrenn, 1982; Winter et al., 2010; Levy et al., 2012).

Water depths possibly ranged from 300 to 900 m (Webb and Wrenn, 1982), though

Wilch et al. (1993) suggest that the necessary thickness of an overriding ice sheet for such depths would be too great and that depths of 300 m or less are more likely. Levy et al. (2012) suggest that the additional ice was supplied by local glaciers and not the ice sheet. The 40 Kyr obliquity-paced glacial-interglacial cycles during the transition time were powerful enough to drive the West Antarctic Ice Sheet (WAIS) and East Antarctic

Ice Sheet (EAIS) beyond McMurdo Sound during glacial periods and cause them to retreat from marine settings during interglacials (Naish et al., 2009; Levy et al., 2012), and sea ice was present only during the winters (Levy et al., 2012). At elevation > 1000 m, polar conditions still prevailed (Marchant et al., 1993; Sugden et al., 1999; Sugden and Denton, 2004).

The dynamic polar to subpolar regime ranged from peak warmth, when Earth’s average surface temperature was 2-3ºC warmer than present (McKay et al., 2012), to extreme polar conditions over the course of the Pliocene (Wilson et al., 2012), responding to global driving mechanisms (Fedorov et al., 2010; Levy et al., 2012). Polar, dry-based glacial conditions persisted at elevations > 1000 m in the TAM (McKay et al., 2009), while at sea level, fluctuating warm-based glaciers extended onto the continental shelf repeatedly. McKay et al. (2009) noted that 35 of the 58 identified unconformity-bound depositional cycles occurred in the Pliocene-Pleistocene, which span only 5 of the core’s

14 Ma of temporal coverage. Foraminiferal assemblages indicate summer sea surface temperatures of 4-5°C until the mid-Pliocene and little to no sea ice, even during the winter (Levy et al., 2012).

The late Pliocene, at ~3.4 Ma, marked the shift toward modern polar conditions, indicated by diatom assemblages characteristic of drier, more persistent glacial regimes

(McKay et al., 2009) and negative shifts in benthic δO18 (Lisiecki and Raymo, 2005). The obliquity-paced cycles, cooler temperatures, and semi-permanent sea-ice fringe have persisted since that transition, with larger-scale variability paced with climate eccentricity rather than orbital obliquity (Levy et al., 2012).

Because evidence of the ice extent at the Last Glacial Maximum (LGM) is preserved around the EVP, it has been extensively studied and documented, ice-covered and ice-free areas have been identified (e.g. Shipp et al., 1999; Denton and Marchant,

2000; Wilch et al., 2011; Ross et al., 2012), and footprints of the glacial extent and flow directions have been reconstructed (e.g. Denton and Hughes, 2000; Figure 8). Footprints of previous glaciation episodes have been obscured or overprinted by activity from the

LGM or other erosional processes and have not been mapped. According to the terrestrial and offshore sediment and morphology records, however, climate over the course of the

Quaternary has been relatively consistent in the EVP, and because there has been little topographic change and consequent consistency in glacial flow paths (Talarico and

Sandroni, 2009; Talarico et al., 2012), a maximum extent for previous Pleistocene glaciations similar to that of the LGM is assumed in this study. Extrapolating this assumption beyond the Pleistocene, however, is not justified, because numerous variables, including the climatic shifts in the Pliocene and development of volcanic edifices that altered glacial flow, would have influenced the ice sheet footprint in the region. Modeling, such as that carried out by Pollard and Deconto (2009), is required to

26 more accurately estimate the total number of glacial advance/retreat cycles and the extent of ice at times older than the LGM.

Figure 8. Flowlines and surface contours of the grounded ice sheet at the LGM (from Denton and Hughes, 2000, Figure 9). 27

Using Scoria Cones as Geomorphic Markers

Many studies have shown that there is a systematic change in scoria cone morphology over time. Morphologic change is clearly observable because cinder cones form with a consistent morphology and the process of cone formation is geologically short-lived, providing little time for environmental factors to affect their shape during their development. An ideal cone, as summarized by Wood (1980a), is a truncated, cone- shaped volcanic hill, built of pyroclastic debris around a circular volcanic vent, with a bowl-shaped crater at the apex. The pyroclastic ejecta comes to rest at angle of repose

(roughly 30°; Figure 9).

Figure 9. A photograph of Merriam Crater in the San Francisco Volcanic Field illustrating the typical morphology of a youthful cinder cone. Merriam Crater is 370 m tall and late Pleistocene in age (from Hooper and Sheridan, 1998, Figure 8) 28

Cones do not always form ideal conical shapes. Syn-eruptive landscape and climate and weather conditions can play a significant role during cone eruption. The construct can be controlled by eruption height and the deposition mechanism of particles, e.g. agglutination or welding of spatter, or avalanching of loose scoria (Kervyn et al.,

2012). Original basal slope can also have a significant effect on cone morphology (Figure

10). Basal slopes of > 5º are important factors in triggering flank collapses and subsequent slope reconstruction by continuing eruption activity that creates complex geomorphology (Kereszturi et al., 2012). Many of these syn-eruptive variations can be systematically accounted for, but their implications are not necessarily consistent across different cone fields, because each field may have characteristic initial cone slopes related to factors such as different eruptive dynamics, environmental interactions, or different stages of activity.

Figure 10. A schematic illustration showing cinder cone morphology and structures with lateral variation in deposits, slope angles, and other factors affecting commonly used morphometric ratios (from Kervyn et al., 2012)

Deviations from ideal cone morphology can provide markers of magma flux and tectonic control on magmatism. Cone height and shape irregularity can be due to pre- eruption surface characteristics, eruption volume, and syn-eruptive processes such as vent migration due to outflow and breaching (Hasenaka and Carmichael, 1985; Kereszturi et al., 2012). Morphologic parameters such as the ellipticity of the cone base and/or crater and the directions of cone breaching are proxies for maximum and minimum stress directions and thus important indicators of tectonic regime and stress control on magmatism (Tibaldi, 1995; Paulsen and Wilson, 2010; Figure 11). Morphometric data on elongate cones and cone alignments can therefore provide constraints on stress regimes active during magmatism from 0-13 Ma in the EVP. Morphologic and structural characteristics of cone arrays controlled by magmatic and/or tectonic stresses in the

Antarctic polar environment may serve as analogues to improve understanding of similar cone alignments on Mars (Bleacher et al., 2009).

Figure 11. A schematic indicating fissure eruption patterns expressed as alignments of circular and/or elongated volcanic vents trending parallel to the subsurface orientation of the fissure (modified from Paulsen and Wilson, 2009, Figure 6C)

Morphometric values are shaped by syn-eruptive processes and stresses during the stages of a cone’s development (a few years to a few thousand years), depending on location and environmental factors; Kereszturi et al., 2012), but following that period, morphometry is affected most by erosional processes. Empirical and modeling studies have identified a range of parameters, including surface slope, rugosity (surface roughness), slope direction, cone height, base diameter, and crater dimensions that can be used to quantify morphologic change (e.g. Hooper and Sheridan, 1998; Parrot, 2007a,b;

Grosse et al., 2012). Where age dates for the cones are available, rates of change have been derived based on these parameters.

For example, the slope of cone flanks decreases in a predictable manner dependent upon environmental factors that control sediment flux (e.g. Hooper and

Sheridan, 1998; Pelletier and Cline, 2007; Inbar et al., 2011; Figure 12). In temperate environments, these factors include precipitation, wind, and biota impact (erosion by 31 animals or resistance to erosion by vegetation rooting). Erosion by precipitation varies according to the amount and frequency. In the southwest US, infrequent, intense rains with enough force to overcome the cohesion of grains cause rilling and gullying on the upper slopes of mature cones, facilitating fast erosion and sediment transport to the apron of the cone and away over time (e.g. Dohrenwend et al., 1986; Johnsen et al., 2010).

Human activity, such as quarrying (e.g. Ice Springs, UT or Red Mountain, AZ) or infrastructure development (e.g. Observation Hill, Ross Island, Antarctica) can also significantly oversteepen cones. Conversely, abundant and aggressive vegetation can help stabilize cone surfaces and slow erosive processes (Inbar et al., 1994).

Figure 12. A plot showing radial-profile evolution of a cinder cone evolving proportional to sediment flux in relation to the diffusivity constant (κ) and time (t), where h and r refer to height and radius of the cone, respectively (modified from Pelletier and Cline, 2007, Figure 1B)

In arid and polar environments, precipitation, vegetation, and animals have diminished or nonexistent roles in morphology modification. The reduced number of

32 variables makes cones in these environments ideal for study. In arid regions in particular, chronologically-calibrated morphologic change has been used to assign undated cones to relative age groupings (e.g. Dohrenwend et al., 1986; Hooper and Sheridan, 1998; Inbar et al., 2011), or to absolute age values over Quaternary time scales (e.g. Dohrenwend,

1987). Kervyn et al. (2012) note that other authors (e.g. Bemis, 2011) have had difficulty developing reliable morphologic indicators of age in more temperate environments due to the higher number of variables.

Glaciers are a variable that is unique to polar and high elevation regions.

Subglacial cones are rare, because subglacial eruptions form deposits controlled by overburden pressure and interaction with meltwater. Cones can be overridden by glaciers and can be modified by ice flow, which can result in block fragmentation (Wright-

Grassham, 1987), cone oversteepening (Porter, 1972), scouring or abrasion, or burial by glacial deposits such as till. The ways in which glaciers modify their substrate are still not fully understood—especially when attempting to discern the differences in behavior between cold- and warm-based glaciers.

The Glacial Erosion Debate

There is little debate among scientists that warm- (or wet-) based glaciers erode the surface beneath them—water facilitates basal sliding, which in turns erodes the subglacial surface (Sugden et al., 2005). The topographic molding abilities of polar (cold- or dry-based) glaciers, however, are not well understood. Most current thought holds that polar glaciers, because they are frozen to their substrate and there is limited or no basal

33 sliding, and because yield strength of frozen sediment is supposedly significantly higher than glacier ice (Williams and Smith, 1989; Waller, 2001), do not contribute substantially to surface erosion (e.g. Holmlund and Näslund, 1994; Sugden et al., 2005; Jamieson et al., 2010), and in fact do more to preserve the landscape than to change it (e.g. Sugden and Watts, 1977).

Numerous examples have been published of preservation of pre-glaciation landscapes in the Northern Hemisphere after being overridden by ice sheets, wherein relict landscapes have been identified using quantitative methods (e.g. cosmogenic exposure dating; Davis et al., 2006; Bierman et al., 2014) and/or principles of geomorphology, i.e. identifying non-glacial and relict glacial surfaces according to physical evidence on multiple scales, including rounding, terraces, tors, and striae (e.g.

Goodfellow, 2007). Additionally, multivariate and autocorrelation sediment analyses at multiple points along glacial drainages have indicated that fluvial sediment transport in and around cold-based glaciers is substantially limited relative to warm-based glaciers and does not provide enough abrading material to significantly impact the subglacial surface (Hodson and Ferguson, 1999).

Recently a number of studies have been published in opposition to this concept, most coming from Antarctica. Fitzsimons et al. (1999, 2000) indicated that, though cold ice (approximately –17 to -18ºC) was much stronger and more resistant to stress than warm ice, localized weakness in the ice could reduce strength and enable deformation of the bed and sediment entrainment. Moreover, failure areas in the ice, such as ice lenses, unsaturated permafrost, structural features (e.g. shear zones), and cavities in the glacier

34 bed could reduce the peak strength of the ice sufficiently to induce bed deformation and entrainment of sediment within the glacier. This would be more likely in perennially frozen areas—a criterion met by the EVP and West Antarctica as a whole—where preexisting surface deformation would be more likely to project topographic irregularities into overriding ice over time (Fitzimons et al., 1999).

Cuffey et al. (2000) used gas content and isotopic composition of the cold-based

Meserve Glacier in Antarctica to argue that the glacier may have formed its U-shaped valley at subfreezing temperatures and without breaking the ice-bed adhesion. Lloyd

Davies et al. (2009) identify recent erosion and deposition features emerging below the cold-based (-30 to -24 ºC) Manhaul Bay and Odell glaciers, superimposed over warm- based glacial tillites in the Allan Hills region of Antarctica.

Cold-based glaciers have been associated with erosional scrapes, grooves, striae, abrasion, and meltwater channels (Fitzsimons et al., 1999, 2000), as well as depositional drift, boulder trains (Figure 13), till patches, ice-cored ridges, moraines, and debris cones

(Lloyd Davies et al., 2009). Deformational features, such as glaciotectonized bedrock, ploughed and overturned boulders, and deformed substrate and permafrost, have also been recognized (Atkins, 2013). In these studies, features preserving original structures and deposits are still recognized. Compressed and flattened ground—i.e. preserved substrate with embedded, but not deformed, grains—as well as windblasted pavement and soils buried by moraines deposited by cold-based lobes of outlet glaciers, are common (Lloyd Davies et al., 2009; Atkins, 2011; Atkins 2013) and more closely match the scale of landscape features observed in studies of warm-based glacial

35 geomorphology. Pavements and moraine-buried soil deposits created by cold-based glaciers can be areally (not volumetrically) similar to deposits created by warm-based glaciers, including moraines, carved valleys, and till patches.

Figure 13. A sequence for cold-based glacier entrainment of boulders and other debris: A. A cold-based glacier that is not advancing and frozen to its bed; B. Upon forward movement of the glacier (i), the margin becomes steeper, leading to marginal overhanging and fracturing (ii); C. Oversteepening of the snout leads to ice block toppling (i), resulting in an ice block apron (ii). The ice block apron is frozen onto the base of the glacier and acts as both a ramp (iii) and a ‘rolling carpet’ for the forward motion of the glacier; D. The apron surrounds and envelopes boulders and debris; E. Incorporation of the ‘rolling carpet’ now includes boulders and debris as well as the ice block apron; F. Boulders are incorporated higher in the basal zone (from Lloyd Davies et al., 2009, Figure 7)

It is notable that, in their analysis of drillcore sedimentary records, McKay et al.

(2009) indicate that there is at least some sedimentary evidence in the ANDRILL AND-

1B core for subglacial erosion in all Cenozoic glacial regimes, indicating that, although

36 polar glaciers are characterized by lower terrigenous sedimentation rates, erosion has occurred in the EVP under both polar and subpolar regimes.

Chapter 3: Methods

Morphometric and Age Analysis of Scoria Cones

All available age data for known cinder cones in the EVP have been compiled

(Appendix A). At the time of this publication, 99 dates were available for cones. A further 123 dates on studied lava flows were traced back to cones using satellite imagery and aerial photographs. An uncertainty scale of 1-3 was used, in which a value of 1 (32 samples) signified the highest certainty, indicated by a sample location on a lava flow clearly emanating from a nearby cone. A date location on an indistinct flow but lying within geographic proximity (within the topographic ‘drainage basin’ of a cone) and a logical pathway (e.g. downslope, in the breaching direction, around an isolated cone) was given an uncertainty value of 2 (48 samples). Locations with indistinct to no evident flow path and ambiguously located within a cone’s geographic proximity were assigned an uncertainty value of 3 (43 samples), indicating the least certainty. Dates from locations not meeting any of these criteria were discarded.

From the dates assigned to cones and flows with uncertainty values of 1 or 2

(Figure 14), 37 cones were selected for study on the following bases: conical topography; minimum surrounding topographic interference; reliable age assignment based on the clear and certain association of a dated sample with the cone; unique fit within the age spectrum of all cones; geographical sampling distribution across the EVP; and digital imagery availability (i.e. no cloud cover, distortion, or other imagery inconsistencies). 38

Cones representing all major and all but two minor centers were chosen. Cones in Taylor and Wright Valleys were determined to be too highly modified or their boundaries too poorly constrained (e.g. located on a valley wall with significantly irregular basal topography) to be useful in ascertaining morphological parameters. Cones have been dated to an age range (0-13 Ma) that spans the transition from warmer glacial conditions to the modern cold, polar desert environment. This age distribution allowed study and analysis of a range of morphologic conditions and their relationship to local and regional environmental factors.

Rates of erosion were established by quantitative comparison of the parameters listed below and used to calibrate a time scale of erosion morphology (e.g. Inbar et al.,

2011). Dimensions and characteristics of cones of the same and different ages were measured in order to establish morphologic change over time. Observed trends in degree of change are used to characterize an average rate of degradation and erosion from a reconstructed, generalized initial cone shape at successive time steps.

Figure 14. A map of the EVP showing the distribution of dated samples from flows and ejecta and the certainty (1 being the highest) with which they were traced back to a cone. Only cones with a certainty of 1 or 2 were kept for this study 40

DEM Construction

Morphometric analysis primarily made use of high-resolution digital elevation data derived from high-resolution WorldView satellite stereo imagery. Airborne Laser

Scanning (ALS) data, also known as LiDAR, acquired during the 2001-2002 austral summer field season through a collaborative project between the USGS, NSF, and NASA

(Csathó et al., 2005), was also used. These data were collected by NASA’s Airborne

Topographic Mapper (ATM) system for calibration of NASA’s Ice, Cloud and land

Elevation Satellite (ICESat) altimeter mission, and provide 2 meter horizontal resolution

DEMs for 5 late Neogene volcanic regions in the Erebus Volcanic Province.

DEMs from stereo imagery were required in order to analyze cones from the full age spectrum of Miocene-Pleistocene cone morphology. For consistency and precision,

WorldView imagery-derived DEMs and orthophotos were used even where LiDAR was available, and were compared with LiDAR for quality control in some regions. Key areas without LiDAR include Brown Peninsula (1.7-2.7 Ma), Black Island (2.5-11.4 Ma), Cape

Crozier (1.0-1.6 Ma), and areas of the Royal Society Range (0.2-14.6 Ma). The imagery from which the DEMs were derived has resolution of 2 m and was acquired by the Polar

Geospatial Center (PGC; P. Morin, pers. comm., 2012), which operates under the auspices of the NSF Division of Polar Programs.

An algorithm developed by Noh and Howat (2015) was used to construct the

DEMs from stereo satellite imagery. The Surface Extraction with TIN-based Search- space Minimization (SETSM) algorithm is fully automated and was designed specifically

41 for sub-meter imagery over varied terrain, including snow, ice, rock, steep slopes, and shadowed topography, the latter three being areas in which previous DEM extraction techniques have struggled (e.g. Cziferszky et al., 2010; Toutin et al., 2013; Howat et al.,

2014). I acquired WorldView-1 and -2 stereo satellite imagery from PGC in National

Transfer Format (.NTF) and converted it to Georeferenced Tagged Image File Format

(GeoTIFF, .TIFF) using a basic repeated command invoking Geospatial Data Abstraction

Library (GDAL) tools from a UNIX terminal. The converted imagery was uploaded to a server and relayed into the cyberinfrastructure of the Ohio Supercomputer Center for processing (Figure 15), which was performed in a parallelized Matlab environment on a

Xeon x5650 processor with acceleration from an NVIDIA Tesla M2070 GPU and a

RAM capacity of 48 GB per node.

Figure 15. A screenshot of the job status interface showing the job ID (one per DEM), session ID, maximum allowable runtime, status (R = running, Q = queued), and elapsed time

The automated SETSM algorithm employed a pyramid strategy to use iteratively finer Triangular Irregular Networks (TINs) to minimize potential search space during 42 weighted normalized cross correlation (WNCC) point-matching between images. Each coarse-to-fine iteration consisted of six steps over the course of which similarity measurements were performed, relative grid height was detected, outliers and blunders were detected based on comparisons with previous iterations, search space was appropriately modified (extended or reduced), and sensor geometric constraints (Rational

Polynomial Coefficients, or RPCs) were updated to reflect recognition of outliers. The last step enabled compensation for geolocation accuracy-based errors caused by possible lack of ground control on RPCs.

DEMs constructed from series of satellite stereo image pairs varied spatially from

1000 to 3600 km2 in area and, as series were constructed all at once rather than by image pair, processing time varied between 12 and 150+ hours depending on the physical size and topographic composition of the area of interest. Output DEMs maintained the resolution of the input satellite imagery and contained no data gaps or artifacts, except very close to the edges and where the images themselves had quality issues (e.g. cloud cover). For most regions, redundancy between satellite tracks and individual images negated these problems.

All quantitative analyses were performed on the DEMs at their full 2 m resolution. Cone selection, areal delineation, and visual analyses were performed using orthoimagery (derived from the satellite imagery during the process of DEM construction) draped over DEM elevation values in ArcGIS 10.2 and ArcScene (Figure

16). The processing power of the desktop computers used was not enough to visualize the

DEMs at full resolution, so a default value of 10 m was used with enhanced raster quality

43 defined in ArcScene to avoid severe pixelation and discrete elevation jumps within the

DEMs.

Figure 16. An illustration showing a SETSM-generated DEM looking north over the Mason Spur area with orthophotography overlain (left) and without (right)

Morphometric Parameterization

From the high-resolution DEMs it was possible to extract the suite of parameters necessary for analyzing change due to erosion, including scoria cone height to width ratio, average and maximum flank slopes and curvature of cone flanks and summit. This was accomplished using a suite of algorithms, packaged as MORVOLC (Grosse et al.,

2012) and NETVOLC (Euillades et al., 2013), run in an IDL environment through ENVI

5.0 software on a Windows 7 operating system.

Initially, manual methods were used to delimit cone boundaries and parameterize cones. I defined a rectangular boundary for each cone and used ArcMap’s 3D Analyst extension to create elevation profiles of four transects oriented to N-S, E-W, NE-SW, and

NW-SE. Each elevation profile showed the full width of the cone. I visually determined slope breaks in the elevation profiles and derived the height based on difference between the highest point and the average of base heights (the elevation on each side at which the slope breaks were evident); the width based on the horizontal distance between the points where the slope breaks; and the average slope based on the height over distance between the highest point and the slope break. The measurements for each profile were averaged to determine the average value of the parameter for the whole cone.

Despite the fact that delimitation and parameterization decisions were based on clear slope breaks and other topographic cues, this method proved to be less consistent than is desirable due to the subjective nature of identifying discrete slope breaks on a continuously changing surface (e.g. Grosse et al., 2012). Grosse et al. (2012) and

Euillades et al. (2013) provide a pair of algorithms. NETVOLC performs the function of delimiting the boundaries of the volcano based on a user-defined center point and the concavity (or negative convexity) of the cone surface to draw a closed path around the best possible set of pixels with maximum concavity (maximum negative convexity;

Euillades et al., 2013; Figure 17). MORVOLC calculates an extensive set of parameters

(explained in Table 1) based on 3D computations from a TIN basal surface interpolated

45 from the surrounding topography (rather than a flat, horizontal base) and the boundary delimited by NETVOLC (Grosse et al., 2012).

Figure 17. A DEM of an idealized volcanic cone. (a) shows the DEM in two dimensions, with point (x0,y0) representing the center; (b) is the profile convexity map of the cone and (c) shows the DEM in three dimensions. The red outline in (a) and (c) represents the cone boundary defined by the concave breaks in slope shown by the most negative values in (b) (from Euillades et al., 2013, Figure 1) 46

I prepared the DEMs for NETVOLC and MORVOLC by isolating and cropping the regional DEM in ArcGIS to an extent that incorporated all the cones visible on that particular DEM (Figure 18). Cropping served to decrease overall processing time. Edifice centers and size of the rectangular area of interest within which the basal boundary of the individual cone was inscribed (e.g. 90,000 m2 for a volcano with a diameter of 250 m, with an arbitrary buffer, in this case 50 m, on each side in case of error in visual estimates of volcano size) were located and entered manually, and the data were stored in a parameter file accessible by the program.

Figure 18. A clipped DEM of Mount Morning draped on orthoimagery with rectangular cone area of interest (containing the cone) outlined in yellow

NETVOLC was invoked through the IDL terminal in ENVI. All parameters were set to default values (Appendix B) except for minimum and maximum threshold separation distances—these defined the limit of pixels from the center within which the solution could be calculated and were therefore varied depending on the size of the cone.

The cone names, coordinates of the center points, and dimensions of the rectangle within which the cones were inscribed were written into a separate text file read by NETVOLC.

The algorithm imported a specified DEM and initially derived maps of profile convexity, slope, and aspect. Two-dimensional profile convexity was calculated by intersecting the cone surface with the plane of the z axis along the orientation of the aspect direction. The resulting profile convexity value was equal to the rate of slope change along the vertical axis (Figure 19).

Figure 19. A schematic diagram showing the intersection of the z (height) axis and the cinder cone surface to derive profile convexity

A slope map, aspect map, and profile convexity map were created by the algorithm for each edifice, along with a shaded relief and clip of the original DEM

(Figure 20).

An ideal cone with an apex at the central point specified in the volcano parameter file was then computed and subtracted from the real cone to determine differential aspect, or facing direction relative to an idealized conical surface, of the real cone surface. This step provided a numerical indicator as to whether pixels were facing toward (differential aspect > 90º) or away from the central point of the cone (differential aspect < 90º). Profile convexity and differential aspect were combined to determine azimuthal curvature, a binary layer mask based on whether the profile convexity was less than 0 (i.e. concave) and the differential aspect was less than 90º (1) or not (0). Pixels with a value of 1 were kept, and pixels with a value of 0 were discarded (ignored). This procedure created a more limited set of possible pixels and mitigated artifacts and excursions smaller than the cone edifice, such as vents and craters, making it easier for the program to compute a closed path around the cone’s central point while ignoring anomalous topographic areas or features.

Figure 20. NETVOLC intermediary outputs for cone CC018, indicated by the star on the inset map, showing A) the shaded relief of the cone; B) slope, where lighter indicates steeper slope; C) profile convexity, where darker shades indicate negative (i.e., concave) values; D) surface aspect, where black represents an aspect of 0º and grades to white at 360º; E) azimuthal curvature, where black = 0 and white = 1; and F) an orthophotograph of the edifice

A minimum-cost network flow (MCF) algorithm was used by NETVOLC to build a node/edge network and a cost map by assigning a value difference-weighted cost to every edge between adjacent nodes (pixels with an azimuthal curvature value of 1). The algorithm determined the minimum cost of a closed-path solution around the central point by identifying the path whose sum of costs between adjacent nodes was lowest. To simplify the solution, the minimization problem was solved in polar coordinates rather than a Cartesian system, so that any solution must encompass the previously defined central point of the cone. Because the minimum and maximum thresholds separation (the minimum and maximum possible distance, respectively, between the defined central point and the edge of the solution) are defined, and because defined areas of interest are larger in length and width than the cone of interest, the solutions are not sensitive to minor errors (± a few meters) in placement of the central point.

Solutions were determined iteratively (usually 10 or less iterations) by calculating a number of solutions, determining the mean and standard deviation of edge costs and cancelling all solutions outside two standard deviations from the mean, repeating the computation to find a new optimal solution until a finite collection of possible solutions is reached, and determining the solution with the lowest normalized cost, which then became the final solution.

Region of Interest files (.ROI) were created which show the georeferenced outline in space of the cones without visual context (i.e. it is not an overlay on the DEM; Figure

21). These files were stored in a specified location, stipulated when initial parameters

51 were entered, and were used with the MORVOLC algorithm to delineate the area of analysis in a consistent, quantitatively repeatable way.

Figure 21. A DEM swatch of Cape Crozier, displayed in ENVI, showing the region of interest (ROI) outlines (in yellow) of cones CC018 (large) and CC008 (small). ROI files contain no elevation information and simply illustrate the outline of the cone edifice

MORVOLC was also invoked through IDL in ENVI. All directory paths necessary for program operation had to be changed manually for each set of cones, but otherwise default values were used for the program (Appendix B). Cropped DEMs and

ROI files (‘contours’) were stored separately, per the program’s operating methods, and a series of parameters were computed for each cone (Table 1).

Table 1. List of morphometric parameters used to characterize volcanic edifices in this study (modified from Grosse et al., 2012, Table 2)

Parameter (unit) Description Size parameters (metric)

Basal area (AB) Planimetric area of the edifice outline

Basal width (WB) Average width of the edifice base calculated as SQRT(AB/π)*2

Major basal axis (MAxB) Length of the maximum base diameter passing through the centroid

Minor basal axis (mAxB) Length of the minimum base diameter passing through the centroid Height (H) Difference between the summit elevation and the elevation of the 3D basal surface below the summit

Maximum height (HMAX) Difference between the summit elevation and the elevation of the lowest point of the edifice outline Volume (V) Volume enclosed between the DEM surface of the edifice and the 3D basal surface

Maximum volume (VMAX) Volume enclosed between the DEM surface of the edifice and a horizontal base with elevation equal to the lowest edifice outline point

Shape parameters (dimensionless)

Ellipticity index of flank contours [array] (ei) Measure of the elongation of the main elevation contours that enclose the edifice

Avg. ellipticity index of edifice (eiAVG) Mean of all ei values Irregularity index of flank contours [array] (ii) Measure of the complexity of the main elevation contours that enclose the edifice

Avg. irregularity index of edifice (iiAVG) Mean of all ii values

Height/basal width ratio (H/WB) Measure the overall steepness of the edifice

Basal width/summit width ratio (WB /WS) Measure of the relative size of the summit region (defined below)

Slope parameters (degrees)

Avg. slope of whole edifice (STOT) Mean slope of the entire edifice

Avg. slope of flank (SFL) Mean slope of the edifice excluding the summit region

Maximum slope (SMAX) Mean slope of the height interval with maximum average slope value

Minimum slope (SMIN) Mean slope of the height interval with minimum average slope value

Standard deviation of slope of whole edifice (SSD) Deviation of slope values of the whole edifice from the mean slope

Orientation parameters (degrees)

Maximum basal axis through summit (αS) Azimuth of major basal axis passing through summit point

Maximum basal axis through base (αB) Azimuth of major basal diameter passing through base centroid

Maximum basal axis orientation (αMAX) Azimuth of the axis of maximum basal width that passes through any point

Average azimuth of flank intervals (αFL) Average azimuth of maximum diameters of main elevation contours on edifice flank

MORVOLC returned an ‘Invalid Projection Name’ error when it was run with the first set of NETVOLC ROIs, then crashed. A few changes were made to the input parameter file to no avail. Communication with Pablo Grosse and Leonardo Euillades quickly revealed that MORVOLC did not recognize and had not been tested on polar stereographic projections, resulting in miscommunication between the algorithm and

ENVI. MORVOLC 1.1 was shortly published with a workaround wherein a projection problem resulted in an error indication (no summit latitude/longitude) in the output parameters rather than a program failure. All other parameters were returned without issue.

Initially MORVOLC used the ROI and DEM to generate a TIN surface, a surface based on a first degree polynomial, and an inverse distance-weighted (IDW) mean surface to represent the 3D basal surface of each cone and match the basal area surrounding the cone. In this study, calculations based on the IDW surface were used exclusively due to a qualitatively determined more accurate fit to the edifice base than the polynomial and TIN surfaces (P. Grosse, pers. comm.; Grosse et al., 2012; Grosse et al.,

2009). Elevation contours were generated with resolution-dependent intervals (in this study, 5 m; Figure 22), and the summit and flank areas were differentiated by identifying the contour intervals between which maximum convexity occurred (i.e. the slope begins to flatten into the summit area) and using that interval as a dividing point between summit and flank, where flank was defined as the area below the interval of maximum convexity, and the summit as the area above. In instances of complex topography (e.g. a crater or multiple peaks), the summit region was defined as the area above the lowest

54 continuous contour line before topography, such as different peaks, dictated division into two or more main contours per elevation value (Figure 22; Figure 23). The edifice flank was separated into main and lower flanks at the elevation of the lowest closed contour

(Grosse et al., 2014). The lower flank comprises the area between the lowest closed contour on the edifice and the edifice boundary.

The basal area of the edifice was found by calculating the area of the two- dimensional ROI. Average basal width was calculated by finding the width of a circle with the same area as the cone outline. Major and minor axes were also calculated using only the cone outline by determining the maximum and minimum diameters of the outline shape. Height was calculated by measuring the distance between the summit and the point on the basal surface directly beneath it, and an additional height measurement recorded the difference between the summit and the lowest point on the outline.

1 kilometer

Figure 22. MORVOLC output figures from cone CC018 (indicated by the red star in the inset map), showing A) the slope of the cone, wherein red indicates higher slope and blue indicates lower (see enlarged scale, in degrees, above figure), as determined by numerical analysis of the contour lines produced by the program; B) 5 m contours generated by MORVOLC showing the delineation between the summit region (above the red line), main flank (between the red and blue lines), and lower flank (below the blue line); C) a shaded relief image of the DEM with flank and summit regions illustrated; D) profiles of the cone from W-E (top) and S-N (bottom); and E) an image in 3D space showing the edifice and outline of the calculated basal surface isolated from surrounding topography 56

Volume was calculated as an integrated sum of differences between DEM elevation and TIN basal surface elevation at each pixel, i.e.

where is the number of pixels in the DEM, is the DEM resolution, and is the height of the DEM and TIN surfaces, respectively, at each successive pixel ( ) until .

Figure 23. Profile of an example cone illustrating the computed TIN basal surface and the edifice height (H), maximum height (HMAX), volume (V), maximum volume (VMAX – not used in this study), and the summit region boundary (modified from Grosse et al., 2012, Figure 4).

Ellipticity index ( ), which quantifies the elongation of the cone, was calculated by dividing the area of a circle with a diameter the length of the long axis ( ) by the area enclosed by a given elevation contour ( ):

A larger indicates a more elongate shape. A mean for all contours was found for each cone and returned as .

Irregularity index ( ) describes the complexity of each contour based on dissection index ( ), and was calculated by relating the area enclosed by the contour and the contour’s perimeter ( ):

, where

and is the dissection index of an ellipse with the property .

An average irregularity index was calculated from all contours as an estimate of the map- view complexity of the edifice as a whole, and to negate bias created by snow cover at the base or summit. Height to basal width ratio was calculated as an estimate of overall cone steepness.

Mean edifice and flank slopes were determined using point data from the generated slope map (Figure 22). Flank slope was used to avoid accidentally considering irregularity in topography from craters at the summit regions of cones in the final results.

Maximum and minimum slopes were computed by finding the mean slope between successive contour intervals and extracting the largest and smallest, respectively. Cones were purposefully chosen to avoid errors associated with extensive snow cover. All chosen cones are judged to be greater than 60% exposed, and all but six (on White Island,

Hut Point, and Mason Spur) are more than 75% exposed. Most have little to no basal

58 snow. Coverage on cones that are surrounded by snow is estimated using the topography of the snow and any exposed areas to determine the approximate cone boundary. Polygon masks covering snow within the cone boundaries are then created in ArcGIS and their areas are calculated. Visual analysis of cone outlines and orthophotographs indicates that apron snow coverage is not detrimental to the delineation and parameterization processes used by NETVOLC and MORVOLC. For cones on White Island, NETVOLC still captured the base of the cone under snow, rather than mistaking the snow line for the characteristic break in slope used to identify cone boundaries.

The presence of snow might result in differences in some parameters; for example, a snow apron might flatten average slope values for the edifice. However, this effect would be negligible in areas where the snow placement reflects the topography

(e.g. on slopes, the bases of most cones). The only areas where it becomes problematic are flat, basin-like areas (e.g. saddles) where the cone base may be buried, or windy areas where a tail might develop on the downwind side of the cone. These scenarios were avoided in the cone selection process.

Though MORVOLC possessed the capabilities to delineate, measure, and parameterize craters, these capabilities were not utilized as the complexities of snow cover, elongation, and breaching made them impractical. Morphometric results for each cone were output into a text file and converted into an excel file. The parameters listed in Table 1 were extracted and translated into a master table in Excel that contained the desired data for every cone parameterized. Here I was able to manipulate, visualize,

59 and statistically summarize the data to determine trends in and rates of morphologic change.

Evaluating Cinder Cone Degradation

Determining Trends in Morphologic Change

Changes in morphology over time were delineated by plotting the parameters measured by NETVOLC and MORVOLC against cone age in Microsoft Excel. Each parameter was plotted on a separate scatter plot and a regression line was fitted to each set of points. Previous work on change in cone morphology with time plotted trends both linearly (e.g. Hasenaka and Carmichael, 1984; Dohrenwend et al., 1986) and, more recently, exponentially (e.g. Hooper and Sheridan, 1998; Pelletier and Cline, 2007;

Fornaciai et al., 2012). Correlation coefficients derived for this study using data from published literature and data generated in this study indicate that an exponential trend provides the best fit for most datasets.

The square of the Pearson product moment correlation coefficient (r), calculated by Microsoft Excel, was used to evaluate suitability of trend fit (e.g. Derrick et al., 1994;

Scally and Owens, 2004):

In this equation, refers to age of the cone, and is whatever parameter is being observed over time (e.g. height to width ratio, slope, etc.). and represent the mean values of each coordinate set. Because this correlation coefficient reflects the linear relationship rather than the exponential relationship between two numerical sets, was used instead of to evaluate the exponential fit, thus:

This returns a value of , which, when squared, reflects the relationship between an exponential trend line and the position of the scattered data points, such that a value of zero reflects a relationship in which the points are completely evenly scattered across the plot, while a value of one represents a relationship in which every single point in lies on the line , where is the value of the given parameter at time , and

is the initial value of the parameter.

is the decay constant, which represents the degradation of a given parameter

(e.g. STOT, H/WB) of a cone at a rate (e.g. versus age) proportional to its value at any given time.

Comparison with Previous Studies

Equations for lines of best fit were derived for slope vs. age and H/W ratio vs. age plots for seven previous studies in addition to this study. Studies were drawn from

61 existing literature for comparison only if they analyzed 6 or more data points spanning more than 1 Ma—shorter time periods tended to produce unrealistically high decay constants (e.g. Bloomfield, 1975; Sucipta, 2006; Table 2; Figure 24) due to the relatively small number of samples and the absence of a degree of morphological stabilization that comes with time. Dohrenwend et al. (1986) note that maximum erosion of cones occurs on the upper slopes, and as the upper slopes erode, the rate of slope loss decreases (Figure

25). Thus a group of cones that are not old enough to show this transition will have an artificially high slope or height/width decay constant.

Table 2. List of cinder cone morphology studies used for comparison of erosion rates. Note that the decay constants for studies covering less than 1 Ma are very high

Source Decay constant Data points Age range of study Location This study -0.088 20 0-8.3 Ma EVP Hoffer et al., 1998 -0.220 6 0-5 Ma PPBF Dohrenwend et al., 1986 -0.201 11 0-1 Ma CVF Fornaciai et al., 2012 -0.114 30 0-3 Ma SVF Hasenaka and Carmichael, 1984 -0.509 11 0-2.8 Ma MGVF Sucipta et al., 2006 -3.455 8 0-0.7 Ma BCCC Bloomfield, 1975 -20.020 6 0-0.04 Ma GCVF Locations: EVP = Erebus Volcanic Province, Antarctica; CVF = Cima Volcanic Field, CA; SVF = San Francisco Volcanic Field, AZ; MGVF = Michoacán-Guanajuato Volcanic Field, Mexico; PPBF = Potrillo/Palomas Basalt Fields, NM/Mexico; BCCC = Bajawa Cinder Cone Complex, Indonesia; GCVF = Grupo Chichináutzin volcanic field, Mexico

0.3 This study Hoffer et al., 1998 0.25 Dohrenwend et al., 1986 Fornaciai et al., 2012 Gilbaud et al., 2012; Hasenaka and Carmichael, 1984 0.2

Hooper, 1994; Hooper and Sheridan, 1998

B Sucipta et al., 2006 0.15

H/W Bloomfield, 1975

0.1

0.05

0 0 2 4 6 8 10 Cone age (Ma)

Figure 24. A plot illustrating the artificial intensity of decay constants derived from short time scales and extrapolated (dashed lines) over long ones. The trends derived from Sucipta et al. (2006) and Bloomfield (1975) are determined from only 0.7 and 0.04 Ma of data, respectively—less than the 1 million years required to begin to see an exponential decrease in slope loss (e.g. Dohrenwend et al., 1986)

Figure 25. Average degradation of cinder cones in the Cima Volcanic Field, Mojave Desert, showing the increase and subsequent decrease in rate of slope loss over 1 Ma (from Dohrenwend et al., 1986, Fig. 7)

All trends derived from previous studies were extrapolated to 9 Ma (the age span of cones in this study) based on their respective equations for line of best fit and plotted on one graph per parameter. Conversely, trends were derived from this study using only subsets of the data (3 Ma to present and 5 Ma to present) to attempt to more accurately compare results with trends determined by other studies. The lines and their correlation coefficients, along with other factors, such as local maxima and minima, were visually and numerically compared to determine how the results of this study fit in with the existing body of literature. The relevant plots and explanations are found in Chapter 5.

Chapter 4: Results

Syn-eruptive Cone Morphology

Cone dimensions

The 37 cones measured display a diversity of dimensions. The cones in the EVP are spread out over time and space, unlike cones of consolidated volcanic fields which have most commonly been the subject of study. The EVP cones are the product of multiple episodes of volcanism and are not necessarily genetically related. Height ranges from 17 to 159 meters, with minimum and maximum values lying in the Royal Society

Range and on Brown Peninsula, respectively. Cones throughout the EVP possess an average height of 70 meters. Geographic distribution of height values is highly variable, e.g. values in the Royal Society Range vary between 17 m and 140 m for cones that are a maximum of 2.3 million years apart. On Brown Peninsula, two cones, which are less than

0.5 million years apart in age, show a difference of 71 m in height. Some areas or age groups show relative consistency in dimensions. The two Hut Point cones have similar heights—43 and 49 m—as do the five cones of Minna Bluff, which range from 34 to 55 m and span ages between 1.99 and 8.32 Ma. The majority of studied cones (24) are between 17 and 74 m in height (Figure 26). Smaller subsets fall between 74-102 m (6),

102-131 m (3), and 131-159 m (4).

The tallest cones are found on Brown Peninsula, White Island, Mount Morning, and in the Royal Society Range (Figure 27). Most cones on Ross Island and Minna Bluff 65 are relatively small (all but one are less than 100 m tall), while the Brown

Peninsula/Black Island/White Island group contains the highest percentage of large cones, with four greater than 100 m tall, all eight greater than 50 m tall, and average height for all eight cones of 94 m. The tallest cones in the EVP were constructed 1-2.25

Ma (4 cones greater than 139 m tall), while the next tallest group were constructed 3.35-

5.0 Ma (3 cones 109-139 m tall). Smaller cones are much more abundant and show no apparent age-related grouping.

Number of cones of Number 4

0 17-46 46-74 74-102 102-131 131-159 Cone height (m)

Figure 26. Equal-interval frequency distribution of cone heights in the EVP. Mean height is 70 m, or 44% of the maximum

Figure 27. An overview map of the Erebus Volcanic Province showing the geographic, temporal, and height distribution of cones. All mapped and associated values are listed in Appendix C

Cone width values also show variation. Widths throughout the EVP range from

122 m to 1405 m and average 620 m. The narrowest and widest cones are found on Mt.

Morning and Brown Peninsula, respectively. Geographic distribution of width values is, like height, widely variable (Figure 28). The Royal Society Range and Mount Morning both show a range of widths—134-957 m and 122-790 m, respectively, for cones in groups formed over 2.24 and 2.95 Ma of volcanic activity. Minna Bluff, by contrast, displays relative consistency in cone widths, with only one of the five cones falling outside the range of 384-591 m. Older cones on Ross Island (i.e. at Cape Crozier and

Mount Bird, 1.29-3.7 Ma) show strong similarity, with values of 721-791 m, while younger cones on Mount Erebus and at Hut Point (0.033-1.00 Ma) are between 202 and

389 m wide.

The Brown Peninsula/Black Island/White Island group again has the highest percentage and concentration of large cones, with four cones wider than 1000 m, seven of eight wider than 878 m (with one small cone on White Island with a basal width of 457 m), and a collective average basal width of 998 m. Overall, the majority of cones (22) have widths between 379 and 892 m (Figure 29). Eight cones are smaller (between 122 and 379 m), and seven are larger (five between 892 and 1148 m and two between 1148 and 1405 m).

Figure 28. An overview map of the Erebus Volcanic Province showing the geographic, temporal, and width distribution of cones. All mapped and associated values are listed in Appendix C\

16 14

12 10 8 6

Number of cones of Number 4 2 0 122-379 379-635 635-892 892-1148 1148-1405 Cone width (m)

Figure 29. Equal-interval frequency distribution of cone widths in the EVP. Mean width is 621 m and, like height, 44% of the maximum

Ellipticity and orientation

Ellipticity and azimuth of elongated axis were measured for all 37 cones. No perfectly circular cones were measured. Ellipticity index (ei) values ranged from 1.10

(nearly circular) on Brown Peninsula to 2.05 for one cone on Mount Morning

(approximately twice as long as it is wide). Unlike height and width values, which adhere to bell-like distributions, most cones (14) have a low ellipticity index between 1.10 and

1.29 (Figure 30). Nine cones have an ei between 1.29 and 1.48, seven have ei values between 1.48 and 1.67, and two cones each have an ei between 1.67-1.86 and 1.86-2.05.

The mean ei is 1.39 and the median is 1.33—31 of the 34 values fall between 1.10 and

1.67, and 19 of the 34 fall below the average ei. Cones with the highest ei values are found on Mount Morning (five cones with ei > average; this has also been suggested by

70 previous research, e.g. Paulsen and Wilson, 2009), Minna Bluff (four cones with ei > average), and in the Royal Society Range (three cones with ei > average), with one additional high ei value each on White Island and Mount Discovery. Groups of cones with the lowest ei are found on Brown Peninsula (both cones with an ei < 1.11), White

Island (two cones with an ei < 1.11), and Cape Crozier (ei < 1.19), with one cone on

Black Island and one on Mount Bird with ei < 1.18. Visual observations in these areas show that some cones are elliptical and, therefore, the cones selected for measurement in this study may not be representative of typical cone shape in each region.

16 14

12 10 8 6

Number of cones of Number 4 2 0 1.10-1.29 1.29-1.48 1.48-1.67 1.67-1.86 1.86-2.05 Ellipticity index

Figure 30. Equal-interval frequency distribution of cone ellipticity index values. Mean ei is 1.39 and 68% of the maximum, though the median is 1.32, indicating that the high value of the few maximum indices is positively influencing the mean—in reality, most of the ei values are low, as shown above

Because minor irregularities in cone morphology can result in an elongated contour and the categorization of cones as elliptical when they are actually nearly

71 circular, an arbitrary threshold of ei > 1.20 was used to define elongated cones (Figure

31). This modification limited the number of elongated cones to 28, with an average ei value of 1.47. An equal-interval distribution normalized to the threshold is shown in

Figure 32. The azimuth of the major axes of only the cones with ei > 1.20 was mapped.

Figure 31. A schematic diagram, with dashed lines signifying values discarded when considering only elongated cones, showing the ideal outlines of a circle (ei = 1.00), the minimum ei value measured in this study (ei = 1.10), the threshold for designation as ‘elongated’ (ei = 1.20), the average ei of elongated cones (ei = 1.47), and the maximum ei measured in this study (ei = 2.05)

4 Number of cones of Number

0 1.20-1.37 1.37-1.54 1.54-1.71 1.71-1.88 1.88-2.05 Ellipticity index

Figure 32. Frequency distribution of cone ellipticity index values considering only ei > 1.2 (26 cones)

Cone orientations vary across geographic space but, in some instances, spatially and temporally related groups of cones are aligned similarly. To determine frequency distribution, elongated cones were grouped into four groups between 0º and 180º at 45º intervals (0º being north; Figure 33). The 11 cones oriented between 0º and 45º range in age from 0.12 Ma to 4.1 Ma. Those oriented between 45º and 90º range in age from 0.23 to 3.35 Ma (seven cones), with an additional 7.5 Ma cone on Minna Bluff. No elongated cones are oriented between 90º and 135º. 10 cones, with ages between 0.03 and 8.32 Ma, were oriented between 135º and 180º.

4 Number of cones of Number

0 0-45 45-90 90-135 135-180 Cone orientation (º)

Figure 33. Frequency distribution of 26 elongated cones according to orientation. 0º is north, and all azimuths are referenced to eastern quadrants

Cones less than 100 Ka are oriented at roughly 137º (Mount Morning and Mount

Erebus). Cones between 100 Ka and 1 Ma are oriented either 85º-90º (Hut Point, Mason

Spur, Royal Society Range) or at 10-20º (Hut Point, Dailey Islands, Royal Society

Range), with two cones on Mount Morning (both at the north end of Riviera Ridge) falling outside of these ranges at 41º and 166º. Older cones on Mount Morning (between

1 and 1.3 Ma) are also oriented at approximately 160º. The oldest cone on Mount

Morning, at 3.07 Ma, lies at the south end of Riviera Ridge and is oriented at 65º. Cones formed between about 1.3 and 5 Ma cover the full range of orientations (Figure 34), from

2º (White Island) to 164º (in the Royal Society Range). Cones formed between 3.07 and

4.10 Ma do show two distinct orientations: approximately 65º (Mount Morning and Black

Island) and 5º (Mount Discovery and White Island). The other elongated cone on White

Island, while younger (2.11 Ma), is similarly oriented at 16º, while a small grouping of 74 cones in the Royal Society Range to the southwest of Heald Island show orientations between 164º (-16º) and 20º. Three of the four cones formed between 7 and 9 Ma show orientations between 138º and 168º on Minna Bluff, roughly parallel to the path of its hook-like shape. The other, also on Minna Bluff, is oriented at 85º.

Figure 34. An overview map showing the age and orientation of elongated cones (non-elongated cones are plotted as circles) in the EVP with the long axis of the diamond indicating azimuth of the long axis. All mapped and associated values are listed in Appendix C 76

Scoria Cone Morphometric Evolution in the EVP

Cones in the EVP show progressive changes in morphometry and slope morphology over time. The mean total slope (STOT), mean flank slope (SFL), mean summit slope (SS), and ratio of cone height to cone width (H/WB) all decrease with time.

Other morphometric parameters (e.g. ellipticity index, irregularity index, summit width to basal width ratio) show no distinct temporal trends.

The youngest cones (< 1 Ma) possess STOT slope angles between 18.2° and 30.5°

(at Hut Point and Mr. Erebus, respectively), which decrease to 15.8° – 19.9° (at Minna

Bluff) for the oldest cone group (7-9 Ma). The decrease in slope is quantified as STOT =

22.081e-0.035a, where a = cone age, with an R2 value of 0.23 (Figure 35a). This equation states that cones initially form with erupted material at a mean angle near 22° and degrade relatively slowly and linearly (an exponent n closer to 0 provides an en value closer to 1, meaning the output value of the equation diminishes little with each input value—this makes the trend appear shallow and almost linear). A 500-iteration Monte

Carlo simulation assuming approximately normal distributions of age (e.g. Kwon et al.,

-0.041a 2 2002) and slope error yielded a very similar equation: STOT = 22.79e . An R value was not calculated for this fit, and the simulation was not performed on other parameters because MORVOLC calculates standard deviation for slope only.

Individual cone morphology varies and cones with increasing age do not necessarily have sequentially lower slopes. For example, MB_039 from Minna Bluff,

77 dated to 1.99 Ma, has a slope of 18.2°, while BP_017 on Brown Peninsula, at 2.25 Ma, has a slope of 23.6°).

Mean values for cones grouped by age show a decreasing STOT trend (Figure 35b;

Table 3). The 8 cones originating in the middle Pleistocene to present have an average total slope of 23.5°; the 13 cones from the early Pleistocene possess a mean slope of

20.8°; the 8 Pliocene cones show an average slope of 18.3°; and the 5 Late Miocene cones have a mean slope of 18.0°. Plotted with a fitted exponential curve, these average values show a rate of degradation similar to the trend line fitted to slope values from individual

-0.032x cones: mean STOT = 22.305e . The correlation coefficient, R² = 0.7462, is dramatically better for the averaged values.

Table 3. Average parameter values for cones based on groupings by cone age (the Pleistocene has been split along a natural gap in the data to illustrate the high frequency of morphometric change in the early stages of degradation). Only mean H/WB and mean STOT were averaged because these are the most commonly used parameters in other studies of cone morphometry

Epoch Number of Cones Mean Age (Ma) Mean H/WB Mean STOT Middle Pleistocene to Present 8 0.242 0.152 23.502 Early Pleistocene 13 1.560 0.130 20.840 Pliocene 8 3.732 0.104 18.301 Miocene 5 8.048 0.079 17.991

(A) Cone Age vs. STOT 35

) 20

(

TOT S 15 y = 22.081e-0.035x R² = 0.2328 10

35 PL2 PL1 P M 30

) 20

(

TOT S 15 y = 22.591e-0.036x 10 R² = 0.8351

0 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000 (B) Cone Age (Ma)

Figure 35. (A) A plot showing the distribution of mean total cone slope versus cone age. Values for all points plotted are listed in Appendix C; and (B) a plot showing mean total cone slope versus cone age average values for the Middle Pleistocene to present (PL2), Early Pleistocene (PL1), Pliocene (P), and Miocene (M) (see Table 3)

Flank slope, which omits the slope of the summit region, also decreases over time, exhibiting a very similar trend to total slope. Younger cones exhibit flank slopes ranging between 18.2° at Hut Point and 30.6° at Mt. Erebus (a 0.1° difference from STOT) and

- older cone flank slopes range from 15.8° to 19.9°, with the relationship SFL = 22.252e

0.035a 2 and R = 0.24 (Figure 36). This is the same decay rate as STOT, but with a slightly lower initial slope.

Cone Age vs. SFL 35

) 20

( FL S 15 y = 22.252e-0.035x R² = 0.2349 10

0 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000 Cone Age (Ma)

Figure 36. A plot showing the distribution of mean flank slope versus cone age. The overall distribution is very similar to Figure 35

A more exaggerated but slightly looser-fitting trend is defined considering only the slope of the summit region of each cone. Cones between 0 and 1 Ma have summit slopes ranging from 16.0° at Mason Spur to 27.2° at Mount Morning, with one outlier,

DI_410 on Daily Island, with a low mean summit slope of 10.4° due most likely to the 80 lack of a crater structure. Cones between 7 and 9 Ma show shallower summit slope values

-0.047a 2 of 11.3° to 15.4°, with slope generally decreasing at SS = 17.914e with R = 0.21

(Figure 37).

Cone Age vs. SS 30

)

° (

S S 15 S

10 y = 17.914e-0.047x R² = 0.2139 5

0 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000 Cone Age (Ma)

Figure 37. Variation of mean cone summit slope with age. A moderate decrease occurs over the course of the Pleistocene and the Early Pliocene to Late Miocene, with the most dramatic decrease occurring between the Early Pleistocene and the Pliocene

Height versus age and width versus age are considered primarily as indicators of syn-eruptive morphology, rather than as reliable erosion metrics, because of the wide range of each parameter. The ratio between cone height and width of the cone base is a parameter that does display a clear temporal trend. H/WB decreases with respect to time at a rate significantly faster than any of the slope parameters and also shows a strong correlation with cone age. H/WB values in the Middle Pleistocene to present bracket

81 range from 0.11 to 0.23, at Mt. Erebus and Mt. Morning, respectively, and decrease to minima of 0.03 at 8.3 Ma on Minna Bluff and 0.05 at 9.0 Ma on Black Island. The trend

-0.096a 2 accompanying these values is H/WB = 0.148e , with a correlation value of R = 0.43

(Figure 38a). Individual H/WB values do not fall on the fitted trendline, however the scatter is more evenly distributed around the trendline, with fewer extreme outlier values, compared with the slope parameters.

Cones that developed during the middle Pleistocene to present show an average

H/WB of 0.152; cones from the early Pleistocene have a mean H/WB of 0.130; the mean

H/WB of Pliocene cones is 0.104; and the H/WB mean value of 0.079 for the Miocene cones is lowest (Figure 38b; Table 3). The curve fitted to these values shows a

-0.082x degradation rate of H/WB = 0.1491e with a significantly improved R² value of

0.9803.

(A) Cone Age vs. H/WB 0.25

0.2

0.15

B H/W 0.1

0.05 y = 0.148e-0.096x R² = 0.4336

0.25 PL2 PL1 P M

0.20

0.15

B H/W 0.10

0.05 y = 0.1507e-0.087x R² = 0.9891 0.00 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000 (B) Cone Age (Ma)

Figure 38. (A) A plot showing cone height to basal width ratio versus age. The distribution is somewhat more uniform with fewer extreme outliers than the slope plots in Figures 19, 20, and 21. All plotted points are listed in Appendix C; and (B) a plot showing the well-correlated trend between average values for H/WB plotted against average age of cones formed in the middle Pleistocene to present, early Pleistocene, Pliocene, and Miocene (see Table 3)

Cone irregularity index (ii), the measurement of the length of the cone’s perimeter relative to that of a smooth circle or ellipse enclosing the area encompassed by the perimeter, shows no clear trend with cone age for the EVP (Figure 5). In temperate environments, irregularity index is a proxy for surface roughness, topographic variability, and drainage density and has been used as a relative dating indicator on cones with active hydrogeologic systems (e.g. Parrot, 2007a), with irregularity index (or contour complexity) increasing as drainages develop over time (Sumner et al., 2002; Johnsen et al., 2010). The apparent absence of an increase in irregularity index with time in the EVP points to differences in surface processes responsible for cone shape degradation in the

Antarctic environment (discussed further in Chapter 5). Based on EVP results, it appears that irregularity index does not provide a relative dating tool for scoria cones in polar environments.

Cone Age vs. ii 2.5

1.5

0.5 y = 1.3244e0.0061x R² = 0.0058 0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 Cone Age (Ma)

Figure 39. A plot showing the distribution of irregularity index (surface complexity) of cones over time.

The WS/WB ratio of summit width, defined as the region encompassing the crater, if present, to basal width, has been considered a valuable morphometric parameter in previous studies, though with debated implications. Some authors have argued that

WS/WB increases with time (e.g. Inbar and Risso, 2001) and others that WS/WB decreases

(e.g. Dohrenwend et al., 1986; Hooper and Sheridan, 1998). Other authors (e.g. Kervyn et al., 2012) have found no statistically apparent variation in this ratio with age or other morphometric parameters, including height, width, elevation, or substrate slope. No clear temporal trend of the WS/WB ratio was found for the EVP. In this study, cone craters were not specifically characterized, so cones with and without craters are not discriminated on the WS/WB plot and some of the scatter may arise from this.

Correlations between basal width to summit width ratios and crater material cohesiveness have been noted in analog studies. These aspects are explored further in Chapter 5.

Cone Age vs. WS/WB 0.6

0.5

0.4

/W 0.3

S W 0.2

0.1

0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 Cone Age (Ma)

Figure 40. A plot showing the ratio of summit width to basal width of cones versus age. Scatter diminishes over time, however, no clear temporal trend is defined

Morphometric Parameters of Glaciated and Non-Glaciated Cones

Cones that were glaciated during the LGM and assumed to be glaciated during prior Pleistocene glaciations (Figure 41) show slightly different morphometry than those that were not glaciated. The 9 glaciated cones yield a rate of decrease in H/WB of

-0.176x 0.1649e with an R² value of 0.1856 (Figure 42), and a rate of decrease in STOT of

24.128e-0.091x with an R² value of 0.1398 (Figure 43). The 12 non-glaciated cones yield

-0.094x -0.117x 2 degradation in H/WB at a rate of 0.145e and in STOT of 24.081e , with R values of 0.1398 and 0.3549, respectively. 86

Figure 41. Glacial flow line map of ice during the LGM from Denton and Hughes (2000) overlying a map of the EVP with locations of studied cones

(A) Cone Age vs. H/WB of Pleistocene glaciated and non-glaciated cones 0.25 y = 0.1649e-0.176x Glaciated R² = 0.1856 Non-glaciated 0.20

0.15

B H/W 0.10 y = 0.145e-0.094x R² = 0.0974 0.05

0.00

0.25 PL2 PL1b PL1a Glaciated Non-glaciated 0.20

0.15

B y = 0.1819e-0.233x

R² = 0.9728 H/W 0.10 y = 0.1545e-0.142x R² = 0.4309 0.05

0.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 (B) Cone Age (Ma)

Figure 42. Plots showing (A) the distribution of height to basal width ratios of Pleistocene glaciated and non-glaciated individual cones; and (B) the distribution of data points for the same cones average grouped into earliest Pleistocene 1 (PL1a), Early Pleistocene 2 (PL1b), and Middle-Late Pleistocene (PL2)

Age groups for glaciated and non-glaciated Pleistocene cones are defined differently than above in order to better suit the shorter time range considered. The oldest 88 group is comprised of cones from the Middle-Late Pleistocene (as defined by Cohen et al., 2013), and the Early Pleistocene cones are split into two groups: early Pleistocene

(corresponding to the Calabrian as defined by Cohen et al., 2013); and earliest

Pleistocene (corresponding to the Gelasian). Height to basal width ratio decreases at

-0.233x H/WB = 0.1819e with a correlation value of R² = 0.9728 on glaciated cones, while

-0.142x on non-glaciated cones it decreases at H/WB = 0.1545e and R² = 0.4309. The lower

R² for the non-glaciated cones is due to the anomalously high value for the Calabrian age cones (Figure 42).

Averaged STOT values for glaciated cones grouped by age decreased at STOT =

24.563e-0.094x with a correlation value of R² = 0.9701, while non-glaciated cones showed

-0.139x a rate of slope degradation of STOT = 24.726e with an R² value of 0.7089. Like

H/WB, the Calabrian point lies off the trendline for the non-glaciated cones (Figure 43).

(A) Cone Age vs. STOT of Pleistocene glaciated and non-glaciated cones 35 y = 24.128e-0.091x Glaciated 30 R² = 0.1398 Non-glaciated 25

º) (

TOT y = 24.081e-0.117x S 15 R² = 0.3549 10

35 PL2 PL1b PL1a Glaciated 30 Non-glaciated

º) 20 -0.094x (

y = 24.563e

TOT R² = 0.9701 S 15 y = 24.726e-0.139x 10 R² = 0.7089

0 0.00 0.50 1.00 1.50 2.00 2.50 3.00 (B) Cone Age (Ma)

Figure 43. Plots showing (A) the distribution of mean total slope of Pleistocene glaciated and non-glaciated individual cones; and (B) the distribution of averaged mean total slope for the same cones grouped based on the same age classification as in Figure 42

Slope and slope standard deviation data were used to complete statistical analyses of the trends of slope on glaciated and non-glaciated cones. Approximately Gaussian distributions of 40Ar/39Ar and K-Ar age errors (e.g. Kwon et al., 2002) and slope standard 90 deviations were assumed, and a 500-iteration Monte Carlo simulation was performed to determine a best fit exponential trend for slope values incorporating error in slope and age. Fits were returned of 23.389e-0.052x and 22.699e-0.043x for glaciated and non-glaciated cones, respectively (Figure 44). These equations have lower mean intercepts and more linear mean decay constants than the equations calculated without considering error. R2 values were not calculated. Standard deviation in decay constants was 0.061 for glaciated cones and 0.046 for non-glaciated cones. Both values are larger than the mean decay constants. This evaluation was not performed on H/WB ratios due to lack of error constraints generated by MORVOLC.

Approximate and conservative pooled t-tests comparing both trends, including their means and standard deviations, were executed and the differences between the trends were found to be statistically insignificant, i.e. the trends were within each other’s range of error.

40 Glaciated y = 23.389e-0.052x 35 Non-Glaciated

)

º 25

(

TOT

S 20

10 y = 22.699e-0.043x 5 0.00 0.50 1.00 1.50 2.00 2.50 3.00 Cone Age (Ma)

Figure 44. Plot showing trends fitted to mean slope values taking into account error in both age and slope

Accuracy of DEMs and algorithms

Polar regions are exceptionally difficult regions over which to extract km-scale, very high-resolution (sub-5 m) DEMs due to extensive low-contrast surfaces and shadowing, extremely high-contrast edges, repetitive textures, and topographic discontinuities and sharp changes like crevasses and iceberg edges (e.g. Moholdt and

Kääb, 2012; Bamber et al., 2013; Noh and Howat, 2015). For these reasons, most DEM extraction techniques in polar regions have focused on highlighting either rock or ice features, based on the type of data used and the goal of the project for which the DEMs are being developed (e.g. Scambos and Haran, 2002; Moholdt and Kääb, 2012). The

SETSM algorithm developed by Noh and Howat (2015) and used in this study is one of the first to effectively create seamless, high-resolution digital elevation models of polar regions from stereo satellite imagery.

For the EVP region DEMs created in this study, absolute elevation data was not utilized, and so vertical and horizontal accuracy of the DEM in space was not systematically evaluated. Three cones on White Island—which, of the five areas with

LiDAR coverage in the EVP containing suitable dated cones, has the fewest gaps in coverage and the highest concentration of cones—and two from ice-free areas on Mount

Morning were delimited on both LiDAR and SETSM DEM and the resulting parameters were compared for consistency and because the LiDAR data were systematically ground- checked and found to be within 0.2 m RMSE using differential GPS checkpoints (Csatho et al., 2005). Input parameters were matched as closely as possible: both DEMs were built on a polar stereographic projection, the same dimensions were used and anchor points of the cone x and y extents were visually matched. Because the LiDAR DEM of

White Island has 4 m resolution while the SETSM DEM has 2 m resolution, it was necessary to round in some instances while converting parameter dimensions to pixel units in the input files (Table 4); however, this was equivalent to no more than a 0.3% difference in actual dimensions and therefore did not have a significant effect on

NETVOLC and MORVOLC comparative analysis. The LiDAR data from Mount

Morning has 2 m resolution, equivalent to that of the SETSM DEMs.

Table 4. Input dimensions in pixel units are determined by dividing the cone bounding box width in meters by the number of meters to a pixel, or the spatial resolution of the image. To maintain integer values, rounding to ± 0.5 pixel units (1-2 m) was necessary

Cone Width (m) Width (pixel units, 2 m resolution) Width (pixel units, 4 m resolution) WI_007 530 265 133 WI_013 660 330 165 WI_045 1070 535 268 MM_003 200 100 - MM_022 730 365 -

Complete results are listed in Table 5. Basal width and maximum height differed by 0-14% and 13-21%, respectively. Differences in area and volume calculations were consequently compounded. H/WB varied by 1-18% and STOT showed differences between

2% and 15%. On White Island, orientations shifted by 7% and 4% for the two cones with ei > 1.2 (see Chapter 4), and by 36% on the cone with ei = 1.2, corroborating the strategy behind using a minimum cone elongation threshold as outlined in Chapter 4. On Mount

Morning, the orientation of the cone with the smaller ei value, MM_022 (ei = 1.3), shifted more than the MM_003 (ei = 1.5)—36% versus 25%, respectively. Some differences, such as irregularity index (3-38% different), are at least partially a product of image resolution. Irregularity index differences highlight the complex interplay between image resolution and parameterization. The two cones that are most similar in size

(WI_007 and WI_013) are both compared at the different resolutions of White Island

DEMs and have the minimum and maximum differences, respectively, in ii between

SETSM and LiDAR, but the largest cones have most of the large discrepancies in ii between extraction methods. This indicates that the differences are not systematic and are likely dependent on, at minimum, cone smoothness, cone size, and DEM resolution. They

94 may further be related to differences between the construction methods of the DEMs themselves; however, an in-depth analysis of this possibility is beyond the scope of this study.

Many authors (e.g. Mashimbye et al., 2014; Maynard et al., 2014; Mora et al.,

2014) have indicated that resolution plays a significant role in the derivation of landform parameters from a DEM surface (Figure 45; Figure 46), even at a difference of only 0.5 m in resolution (Mora et al., 2014), but none have determined a systematic, predictable correlation in resolution and error in measurement, except that lower resolution tends to result in flatter parameter trends (e.g. Maynard et al., 2014). In order to evaluate this assertion thoroughly, equal and redundant coverage of LiDAR data and WorldView satellite imagery in the EVP would be necessary and are not presently available.

SETSM is a viable DEM extraction method from which morphometric parameters can be derived. Differences between LiDAR and SETSM DEMs may be due to data resolution, satellite imagery orthorectification, and extraction processes. SETSM was validated by Noh and Howat (2015) for composite strips comprised of multiple DEMs against ILATM1 B LiDAR data. Validation results by Noh and Howat (2015)returned

RMSE values for the offset between matched points in 3D space of 2.48 m in x, 2.88 m in y, and 2.01 m in z. Minimum differences were found to be 1.24 m, 0.35 m, and 0.41 m, respectively. Maximum differences in each dimension were found to be less than 4 m, or two DEM pixels. These differences, which on the smallest measured cone would affect lateral dimensions by a maximum of 3%, may be more significant on cones in the vertical dimension (up to 13%). The comparison in Table 5 indicates that differences in height

95 between SETSM and LiDAR are usually more pronounced than differences in width, although it is difficult to tell whether differences in boundary delimitations or discrepancies in vertical data registration are primarily responsible.

Table 5. Comparison of key parameters as calculated via NETVOLC and MORVOLC for the same three White Island cones using SETSM- and LiDAR-derived DEMs. For a complete listing of parameters and variable names, see Table 1 in Chapter 3

Cone WI_007 WI_045 WI_013 Parameter SETSM LiDAR % Difference SETSM LiDAR % Difference SETSM LiDAR %Difference

WB (m) 448.23 416.36 7% 756.08 652.11 14% 456.91 437.35 4%

MAxB (m) 513.07 540.00 -5% 835.38 797.00 5% 563.79 527.53 6%

HMAX (m) 92.78 81.04 13% 74.40 58.81 21% 94.74 75.53 20%

HIDW (m) 28.93 21.92 24% 41.80 35.67 15% 49.97 43.86 12%

iiavg 1.05 1.08 -3% 1.95 1.46 25% 1.85 1.15 38%

H/WB 0.06 0.05 18% 0.06 0.05 1% 0.11 0.10 8%

STOT (º) 14.06 12.86 9% 11.92 10.17 15% 16.75 16.30 3%

αMAX (º) 48.79 36.87 7% 86.71 21.80 36% 38.37 31.04 4% Cone MM_003 MM_022 Parameter SETSM LiDAR % Difference SETSM LiDAR % Difference

WB (m) 122.47 122.80 0% 656.35 563.08 14%

MAxB (m) 148.01 133.21 10% 766.60 750.45 2%

HMAX (m) 33.73 28.42 16% 107.26 129.28 -21%

HIDW (m) 17.50 15.56 11% 67.20 58.09 14%

iiavg 1.05 1.21 -16% 1.64 1.16 29%

H/WB 0.14 0.13 11% 0.10 0.10 -1%

STOT (º) 22.32 19.92 11% 19.70 19.22 2%

αMAX (º) 90.77 45.21 25% 236.06 170.46 36%

NETVOLC and MORVOLC derivations were compared with manual parameter determinations for WI_007, WI_045, and MM_003. Cones were manually delineated by visually estimating slope break around the cone. Manual measurements were performed by creating four cross-sections (in cardinal and ordinal directions) and measuring width and height on each cross-section based on the slope break delimitation. Average slope 96 was then calculated by dividing average height by half of the average width and converting from grade to slope. This method returned parameters between 1% and 31% different from MORVOLC output. Differences did not appear to be systematic among individual cones or across different cones. It is likely that this simple analysis of profiles is not comprehensive enough to observe the intricacies of cone topography and morphometry captured by the array-based analyses of MORVOLC and NETVOLC.

Figure 45. MORVOLC-derived cone boundary delimitations from SETSM (left) and LiDAR (right) of cone WI_013 overlain on a shaded relief (top) and topography (bottom). The finer resolution of the SETSM-derived DEM changes the solution cost map utilized by NETVOLC in delimiting cone boundaries by providing additional low-cost pathways as well as obstacles to boundary continuity

Figure 46. Plots showing slope values and accompanying frequency histograms derived by MORVOLC from SETSM (left) and LiDAR (right) for cone WI_013. The finer spatial resolution of the SETSM DEM, especially in the highlighted areas, may contribute to its 15% higher calculated mean slope value. The differences are also likely compounded upon the differences in boundary delimitation created by data of different spatial resolutions (see Figure 63)

Chapter 5: Discussion and Conclusions

Cinder Cone Eruptive Variability

There is substantial consistency in cone edifice shape (Wood, 1980), yet there is also considerable variability in any given morphological parameter between individual cones within volcanic fields. Some of this variability is attributed to source controls including geochemistry, volatile content and viscosity, magma temperature, and magma ascent rate (e.g. Connor, 1990; Martin and Németh, 2006; Valentine et al., 2007; Risso et al., 2008; Di Traglia et al., 2009); some to structural controls (e.g. Connor, 1990; Connor et al., 1992; Corazzato and Tibaldi, 2006; Paulsen and Wilson, 2009, 2010; Rooney et al.,

2011); and some to the topographic relief of the terrain during emplacement of cones

(e.g. Settle, 1979; Wood, 1980; Head and Wilson, 1989; Valentine et al., 2005;

Kereszturi et al., 2012; Kervyn et al., 2012). Little consensus exists as to whether these variables lead to systematic and predictable changes in cone morphology. Cones in the

Erebus Volcanic Province show extensive diversity in non-erosion-related morphological characteristics. Some are potentially significant differences from cinder cones parameterized and analyzed in previous studies. It is important to note that only a subset of EVP cones was measured in this study and the morphologies documented may not fully represent the morphologic range of the EVP as a whole.

100

Variation in cone dimensions

Cone height in the EVP varies from a minimum of 17.3 m in the Royal Society

Range to a maximum of 158.8 m on Brown Peninsula, with an average of 70.1 m.

Diameter ranges from a minimum of 122.5 m on Mt. Morning to 1404.7 m on Brown

Peninsula, with an average value for all 37 cones of 620.6 m. Cone volume is commonly correlated with eruption volume and cone spacing (e.g. Settle, 1979). In this study of the

EVP, a minimum cone volume of m3, maximum volume of m3— a difference of three orders of magnitude—and average of m3 were calculated.

Cones emplaced in comparable tectonic settings tend to have similarities in original dimensions, but edifice size does not appear to provide a diagnostic signature of a particular setting (Table 4). Cones originating in intraplate settings have smaller minimum widths and heights than cones emplaced in subduction-related volcanic arcs and rifting environments (Table 6), but average values don’t show as distinct a trend.

Compiled data from Fornaciai et al. (2012) show similar distinctions: cones in intraplate settings have the lowest minimum heights and widths, cones in subduction environments have the highest minimum heights, and maximum widths are variable and not generally assignable to a specific tectonic setting.

101

Table 6. Minimum, maximum, and average cone dimensions for previously studied cone fields

Width (m) Height (m) Group Geologic Setting Source Min Max Mean Min Max Mean EVP 122 1405 621 17 159 70 Rifting/hotspot This study KCF 200 1600 673* - - - Rifting/hotspot Settle (1979) BDS 204 1214 539 22 219 81 Hotspot Kereszturi et al., 2013 MKCF 100 1450 452 10 200 45 Hotspot Kervyn et al., 2012 LCF 50 1500 460 - - 49 Hotspot Kervyn et al., 2012 PPBF 40 1146 532 9 133 54 Rifting/subduction? Hoffer et al., 1998 SVF 446 1797 1086 48 230 129 Rifting Hooper, 1994; Hooper and Sheridan, 1998 CVF 400 915 588 50 155 93 Subduction Dohrenwend et al., 1986 MGVF 400 1868 913 30 392 154 Subduction Gilbaud et al., 2012; Hasenaka and Carmichael, 1985 Group: EVP = Erebus Volcanic Province, Antarctica; KCF = Kilimanjaro Cone Field, Tanzania; BDS = Bandas del Sur, Canary Islands; MKCF = Mauna Kea Cone Field, HI; LCF = Lanzarote Cone Field, Canary Islands; PPBF = Potrillo/Palomas Basalt Fields, NM/Mexico; SVF = Springerville Volcanic Field, AZ; CVF = Cima Volcanic Field, CA; MGVF = Michoacán-Guanajuato Volcanic Field, Mexico; * = median value; - = no data reported

Figure 47. H vs. WB plot for compiled cone field data. Warm tones correspond to extensional environments, cold tones to subduction-related magmatism, green to trans-American volcanic belt activity, and violet to intraplate settings. CVF, SVF, and MGVF are the same as in Table 6 (modified from Fornaciai et al., 2012, Figure 9)

102

The KCF and BDS cone fields, found in hotspot settings, have cone dimensions most similar to the EVP, with mean widths ± 13% or 82 m and mean heights ± 16% or 11 m. The similarity may be related to the fact that KCF and BDS (and MKCF, LCF) are predominantly located on volcanic centers (i.e. they are volcano cone fields as defined by

Settle, 1979) and not, as with SFV, PPBF, CVF, and MGVF, in platform cone fields.

Settle (1979) noted that across three volcano and three platform cone fields, cones in the platform fields have larger basal diameters and lower initial heights (Figure 48). Settle

(1979) attributes the generally smaller diameters of volcano field cones to the prevalence of volcanic rifting-induced fracture zones on volcano flanks, which allow eruptive activity to migrate with relative ease, thereby limiting the growth of individual edifices.

Platform cone fields, by contrast, have relatively homogeneous overburden pressures and magma rises through preexisting, laterally discontinuous fractures. Regionally homogeneous lateral stresses and low regional slopes mean that fractures do not propagate as easily and the lateral migration of conduits and eruptive centers due to gravity is not promoted.

The Erebus Volcanic Province is not one distinct cone field, and is more complex than previously documented fields because it contains cones built across a variety of terrain. Cones on Mount Morning, Mount Erebus, Mount Terror, and Mount Discovery comprise separate volcano cone fields on each respective edifice, similar to Mauna Kea, or Mt. Etna. Hut Point, Black Island, White Island, Brown Peninsula, Minna Bluff, and the Royal Society range are more difficult to classify. None have the flat basal topography of platform cone fields (Settle, 1979). Cones in these regions are not

103 superposed on major volcanic centers and they lie on complex, heterogeneous topography.

Figure 48. Combined relative frequency distributions of (A) cone basal diameter, and (B) cone height (from Settle, 1979, Figure 2)

104

Initial slope variability

Cone slopes immediately after formation were suggested by Wood (1980) to be at angle of repose for the basaltic material (26-30º) erupted from the cone. In this study, cones less than 300 Ka are considered to be ‘fresh’, because the onset of slope degradation documented in this and previous studies (e.g. Porter, 1972 in conjunction with dates from Wolfe et al., 1997; Bemis e al., 2011) does not appear until after this time. This cutoff is applied to all cones (glaciated and unglaciated) because too few data exist to suggest that divergent trends appear within this time frame for different glacial conditions. Fresh cones in the EVP have slopes between 19.4º and 30.6º. Extrapolation of slope vs age trendlines for EVP cones yields an initial slope of 24.2º.

This value appears low considering the generally basaltic composition of EVP cones; however, it is actually higher than average initial slope values I extrapolated for cones from other regions. A curve extrapolated from data from Fornaciai et al. (2012) predicts an initial slope of 19.6º in the San Francisco Volcanic Field and the curve fitted to data from Gilbaud et al. (2012) predicts an initial slope of 22.2º in the Michoacán-

Guanajuato Volcanic Field (Figure 36). These results indicate that cones do not necessarily form with slope angles that conform to slope predicted from the ideal rheologic properties of basalt. Initial slope angles of 26.6º and 24º were found for Etnean cones and cones in the Guatemalan-Salvadoran volcanic field by Favalli et al. (2009) and

Bemis et al. (2011), respectively.

Height to width ratios of EVP cones are lower than values found in other cone fields (e.g. Hasenaka and Carmichael, 1984; Dohrenwend et al., 1986; Hoffer et al., 1998;

105

Guilbaud et al., 2012). Height to width ratios are affected by the same syn-eruptive factors that dictate initial cone slope angles, including magma source controls, underlying structure, and existing terrain morphology. Benefits and problems with using height to width ratios have been discussed by previous authors. Height to width ratios are not affected by the existence or size of a crater or topographic irregularities (e.g. multiple peaks, parasitic vents) but, unlike slope, height to width ratios are susceptible to variation based on degree of burial by subsequent lava flows (Favilli et al., 2009). Thus ratios are used in addition to slope and surface-based parameters to derive a more comprehensive picture of the factors affecting cone emplacement and subsequent degradation.

Previous studies of primarily Quaternary monogenetic volcanic fields have yielded consistent average H/WB ratios of 0.17-0.18 (e.g. Porter, 1972; Settle, 1979;

Wood, 1980; Dohrenwend et al., 1986; Kervyn et al., 2012). The EVP cones measured in this study yielded an overall average H/WB of 0.12 and an average H/WB for cones less than 300 Ka of 0.13. The overall EVP average is similar to mean values determined by

Kervyn et al. (2012) for cones on Mauna Kea, and the maximum H/WB found in this study, 0.22 on one of the youngest cones, is similar to the common initial (prior to post- emplacement degradation) H/WB value for cinder cones observed by Settle (1979) on Mt.

Etna and Mauna Kea, both volcano cone fields. Fornaciai et al. (2012) determined from data compiled from multiple studies that cones emplaced in intraplate settings have low average H/WB values (0.11) compared with cones from other environments, e.g. subduction zones (0.15), but the authors indicate there is not sufficient data to analyze the origin of the difference.

106

Cones in the EVP, like those on Mauna Kea, are primarily found perched on the flanks of a central volcano edifice or on mountainous hillslopes, rather than in a more topographically level platform volcanic field. Cones formed on slopes can be asymmetric, yielding inaccurate height and base measurements due to incorrectly defined cone boundaries (e.g. Settle, 1979; Favalli et al., 2009; Inbar et al., 2011; Kervyn et al.,

2012) and parameterization error resulting from incorrect interpolation of the IDW basal surface beneath the cone edifice. They are also the cones with the highest probability of syn-eruptive structural or eruptive deformation, and they are therefore more likely to be partially covered by lava. This has the effect of decreasing H/WB because cone height tends toward 0 as lava (its perceived base) builds upward, whereas the cone width tends toward the width of the crater (Favilli et al., 2009).

Maximum EVP height values, as measured from the lowest pixel on the cone base, are an average of 49% higher than heights calculated from the mean value of the cone’s inverse distance-weighted mean interpolated surface, indicating a high degree of asymmetry across the province. Previous authors (e.g. Favilli et al., 2009) have noted the effect of basal slope on asymmetry. Basal slope is defined as the slope of the area around the cone excluding the edifice itself. The surface beneath the cone is the IDW basal surface, which can reflect topographic irregularities in the immediate vicinity of the cone and is therefore not by itself a reliable indicator of slope of the broader area around the cone. In this study, because MORVOLC does not return a basal slope parameter, it was manually determined for each cone by calculating the average slope between the endpoints on cone profiles oriented S-N, E-W, and along the maximum basal axis.

107

Overall basal slope was assumed to lie in the direction of the profile with the maximum basal slope value.

Of the 37 cones studied, basal slope data could not be gathered for 3 due to the presence of data gaps in DEMs in areas around the cones, leaving 34 cones for asymmetry analysis. Twenty-five of these are considered elongated (ei > 1.2). Favalli et al. (2009) noted that basal slopes < 5º (“shallow”) show relatively little control over cone asymmetry and variation in H/WB due to the consistency between HIDW versus HMAX.

This was also the case in the EVP, with cones with basal slopes < 5º displaying an average H/WB of 0.11 and a 44% difference, on average, between HIDW and HMAX. Cones with basal slopes > 5º display an average H/WB value of 0.13 and a 56% difference between HIDW and HMAX, indicating that cones on these slopes can have HMAX values in excess of one and a half times that of the average IDW calculated base. Sixteen cones lie on “steep” basal slopes (> 5º). Nine cones, of which 4 are located on Mount Morning, 3 in the RSR, and 1 each on Hut Point and Mason Spur, are both elongated and possess steep basal slopes.

Of the 9 cones exceeding the slope and elongation thresholds, 8 have a dominant basal slope direction parallel or subparallel to their elongation directions. All 8 show asymmetry, with a mean difference between HIDW and HMAX of 56%. On the 4 Mount

Morning cones, basal slopes reflect the conical nature of Mount Morning itself, indicating both structural and topographic control on asymmetry. The relationship between structure, topography, and cone emplacement is more complex in the RSR. Two of the cones appear to be built on opposing sides (N and S) of the preexisting topography of the

108

N-S aligned Bulwark and they may be aligned parasitic vents (e.g. Armstrong, 1978;

Mankinen and Cox, 1988) which are also oriented parallel to the slope of the conical edifice. The other RSR cone lies just off a ridgetop above Pipecleaner Glacier and is asymmetric in the downslope direction. The cone on Mason Spur is elongated parallel to prevailing slope direction toward the Ross Ice Shelf related to the main edifice of Mount

Morning. One Hut Point cone is elongated parallel to Hut Point ridge on the ridgetop, perpendicular to the local dominant slope, reflecting solely structural control (Kyle et al.,

1992). Seven cones with basal slopes > 5º show no elongation, indicating that slope does not always dictate asymmetry.

Sixteen cones possess basal slopes between 0 and 5º. These are predominantly located on Minna Bluff (six), Black Island, RSR, and Mount Morning (two each), with one each on Brown Peninsula, Hut Point, Juergens Island, and Mount Discovery. 14 are elongated, and 10 have elongation directions parallel to basal slope direction, indicating that in the EVP asymmetry is affected by nominal slopes, even though low slopes may not strongly affect the magnitude of asymmetry. Two cones that are not elongated parallel to basal slope are found on Minna Bluff (alongside 4 cones that are) paralleling the bluff and perpendicular to dominant slope, one is one White Island, and one is on

Mount Discovery. The apron of the White Island cone (not the crater or edifice) is elongated, and so elongation may be due to environmental factors (e.g. wind) or modification of topography by glacial deposits (Wright and Kyle, 1986). Differentiation between slope and structural control would require parameterization of additional cones proximal to the ones mentioned above to determine whether a trend in alignments exists

109 and whether the cone elongation trends are independent of slope, possibly indicating structural control. If no trend in orientation exists but all the cones are aligned parallel or subparallel to topography, slope control would be implied.

The 2 cones that have basal slopes of 0º, located on Juergens Island (in the Dailey

Islands) and Black Island, are elongated. Nothing exists in the satellite imagery to indicate why Juergens Island is elongated, and no definitive evidence exists as to why

Black Island cones are elongated, though structural control is suggested by Wright and

Kyle (1986) and Kyle et al. (1992).

The majority of cones in the EVP are asymmetric to at least some degree, and most asymmetric cones are asymmetric parallel to the orientation of their basal slopes.

The geography of cone elongation is further discussed below (see Ellipticity). For those cones that are not elongated, preexisting topography anomalies resulting in conduit irregularities, inclined lava fountains, or uneven settling surface, or environmental factors such as wind (Mattsson and Tripoli, 2011; Kervyn et al., 2012) may have played a role in their formation.

110

Figure 49. A schematic illustration of an asymmetric cone with an average base height calculated from an inverse distance-weighted mean (IDW) approximately half the height of the max

Wood (1980) suggested that H/WB is independent of lava/magma composition.

However, other authors (e.g. Head and Wilson, 1989; Riedel et al., 2003; Valentine et al.,

2005; Rowland et al., 2009) have indicated that grain size distribution and contrasting internal structures associated with dynamic eruption processes do have effects on cone growth mechanics, slope, and height/width ratios. These dynamic processes can include eruption column longevity and magma fragmentation depth and efficiency (Martin and

Németh, 2006). Bemis et al. (2011) postulated that low slope angles form when vents cease erupting before the erupting material reaches the angle of repose. The presence of water may also affect initial cone morphology (e.g. Carracedo et al., 1992; Kervyn et al.,

2012) by producing smaller grains and resulting in lower slopes such as the 10-22º slope values observed in phreatomagmatic episodes on the Canary Islands by Clarke et al.

(2009). High water content, however, is more likely to result in formation of maars and

111 tuff rings in place of scoria cones (Risso et al., 2008), and scoria cones dominate the

EVP.

Ellipticity

Ellipticity index, considered to be an indicator of structural control on the location and orientation of magma conduits (e.g. Tibaldi, 1995; Paulsen and Wilson, 2009; Figure

11), ranges from a maximum of 2.02 at Minna Bluff to a minimum of 1.10 on Brown

Peninsula. High ellipticity values (elongated cones, ei > 1.2) are generally found on

Minna Bluff and on Mt. Morning, whereas low values (more circular, ei < 1.2) are found on Brown Peninsula, White Island, Black Island, and at Cape Crozier (Figure 34). These locations are also known to have elliptical cones (e.g. Wright and Kyle, 1986) which were not included in this study due to lack of age constraints. Cones in the Royal Society

Range and on Ross Island vary widely in ellipticity. Only Mt. Morning has been systematically studied to determine whether and why cones preferentially are oriented.

Paulsen and Wilson (2009) used Mt. Morning, a locale with an abundance of age- constrained elongated cones and cone alignments, to derive stress directions during

Pleistocene volcanism and rifting. They determined that elongated cones and vent alignments reflected a maximum horizontal compressive stress trending NE-SW, parallel to rift-related normal faults (Figure 50) during the Pleistocene. Regional results on elongation directions of Pleistocene cones measured in this study are generally consistent with this result, with approximately half of the young cones on Mount Morning, in the

112

Royal Society Range, on the Daily Islands, on White Island, and on Hut Point oriented N to NE.

Figure 50. Satellite image showing horizontal maximum (SH) and minimum (Sh) compressive stress directions relative to major structural and volcanic features of the Erebus Volcanic Province. D = Mount Dicovery; E = Mount Erebus; T = Mount Terror; B = Mount Byrd (from Paulsen and Wilson, 2009)

Of those cones in the Pleistocene group that are not oriented N-NE, two highly elongated cones (1.45 < ei < 2.05, aligned at ~160º) on Mount Morning are located proximally to the summit caldera and may have been controlled by stresses around the conduit (“hourglass pattern”, Paulsen and Wilson, 2009; Figure 51). The remaining

Pleistocene cones have lower ellipticity indices (ei < 1.31) and the mechanism of their shaping is unclear. Wind effects have the potential to play a strong role in eruptive processes by carrying lava fragments and abrading and shaping cooling surfaces (Kervyn 113 et al., 2012). Atkins and Dunbar (2009) note that aeolian erosion is thought to be particularly effective in polar regions because of wind persistence, speed, and the density of cold air. Though paleo wind patterns are not well-constrained, current prevailing winds

(Figure 52) and the degree of their persistence (e.g. O’Connor and Bromwich, 1988; van den Broeke and van Lipzig, 2003) are probably substantial enough that wind may have a significant effect on airborne particles (e.g. Sinclair, 1988; Atkins and Dunbar, 2009). It is also possible that the cone structures were syn-eruptively controlled by structural components, but it is feasible that their surface morphology is controlled instead by surface-environment interactions.

Figure 51. A schematic illustrating the pattern of fissures around a summit caldera in a differential stress field, where the caldera and associated conduit locally control the stress field but cease to exert influence at greater distance (from Paulsen and Wilson, 2009, Figure 6B)

114

Figure 52. Streamlines of prevailing wind around Ross Island indicated by directional arrows (from Sinclair, 1988, Figure 1)

Pliocene and Miocene cones reflect different orientations. Most, with the exception of one on White Island, are elongated in the NW-SE quadrants. Wright and

Kyle (1987a) note Late Miocene-aged north to northwest trending alignments of cones at the northwestern end of Minna Bluff and similarly trending dikes near the southeast end.

Paulsen and Wilson (2009) report that a WNW elongate dome on Mason Spur is Miocene in age. Approximately northwest elongation of cones of Pliocene and Miocene age may

115 record the contemporary regional stresses; however results from this study using only cones with well-constrained ages do not provide strong constraints. Morphological analysis of additional cones and quantification of alignments is needed to more thoroughly understand how EVP cone elongation relates to regional stresses.

It is also possible that overriding by glaciers has preferentially scoured cones to elongate them in the direction of ice flow. A few cones on Hut Point, Juergens Island, and possibly Mount Morning, show alignment with the direction of glacier flow (Figure

53). However, the majority do not and, in some cases (e.g. White Island), cones actually show elongation perpendicular to ice flow directions. If this elongation is shown to be caused by crustal stress control, than this contrast between ice flow direction and cone elongation may indicate that cones that have been overridden by cold-based glaciers can retain their original configurations without significant shape modification and can therefore be used to constrain regional structure.

116

Figure 53. Map of the EVP overlain by the LGM ice flow and extent map by Denton and Hughes (2000) showing the age and elongation direction of cones

117

Comparison of EVP Cone Degradation with Cinder Cone Erosion in Non-Polar

Localities

Most previous studies have used H/WB ratio and/or STOT morphological parameters of cinder cones to investigate cone degradation with time, so these are selected for comparisons with EVP morphologic change (Table 7). EVP cones document exponentially decreasing trends in H/WB ratio and STOT with time, similar to degradation patterns of cones from other locales. However, there are a variety of differences between the morphological evolution of cones in temperate environments compared with the EVP polar environment.

Cinder cones initially have a relatively small size and have a geologically short lifespan, such that no studies have observed cones older than Miocene in age (e.g.

Rapprich et al., 2007). Hence, studies of age-constrained morphological change of cinder cones are typically limited to time spans between a few thousand years and around three million years, with one extending to five million years (Hoffer et al., 1998). This study of the EVP covers a time span of ~9 Ma. To compare EVP results to those covering shorter time spans, data from previous studies were extrapolated to match the length of this study and subsets of data from this study (cones aged 0-3 Ma and 0-5 Ma) were used (Table 7;

Figure 54; Figure 55).

118

Table 7. Compilation of cinder cone morphological parameters and degradation rate and comparison with results of this study

Rate Type R2 Points Age Range Source Location 0.148e-0.096x H/W 0.4336 34 0-8.3 Ma This study EVP 0.1503e-0.112x H/W 0.2641 28 0-5 Ma This study EVP 0.1528e-0.132x H/W 0.1693 22 0-3 Ma This study EVP 0.1757e-0.22x H/W 0.7614 6 0-5 Ma Hoffer et al., 1998 PPBF 0.1723e-0.201x H/W 0.181 11 0-1 Ma Dohrenwend et al., 1986 CVF 0.1395e-0.114x H/W 0.0971 30 0-3 Ma Fornaciai et al., 2012 SFVF 0.1939e-0.394x H/W 0.6572 25 0-2.8 Ma Gilbaud et al., 2012; Hasenaka and Carmichael, 1984 MGVF 0.2018e-0.545x H/W 0.5386 14 0-1.7 Ma Hooper, 1994; Hooper and Sheridan, 1998 SVF 22.081e-0.035x S 0.2328 34 0-8.3 Ma This study EVP 23.868e-0.092x S 0.393 28 0-5 Ma This study EVP 24.027e-0.1x S 0.2593 22 0-3 Ma This study EVP 19.589e-0.181x S 0.1731 34 0-3 Ma Fornaciai et al., 2012 SFVF 22.242e-0.289x S 0.5139 14 0-1.8 Ma Guilbaud et al., 2012 MGVF 27.24e-0.643x S 0.5091 14 0-1.7 Ma Hooper, 1994; Hooper and Sheridan, 1998 SVF Locations: EVP = Erebus Volcanic Province, Antarctica; CVF = Cima Volcanic Field, CA; SFVF = San Francisco Volcanic Field, AZ; MGVF = Michoacán-Guanajuato Volcanic Field, Mexico; PPBF = Potrillo/Palomas Basalt Fields, NM/Mexico; SVF = Springerville Volcanic Field, AZ

Cones studied in non-polar volcanic fields tend to have a higher initial H/WB

(0.18 to 0.19 versus 0.15 for polar cones), with the exception of the San Francisco

Volcanic Field, which has slightly lower H/WB (Fornaciai et al., 2012) than the polar cones (Figure 54). Conversely, older cones in this study were found to have higher H/WB than those of the MGVF (Hasenaka and Carmichael, 1984; Guilbaud et al., 2012), the

PPBF (Hoffer et al., 1998), and the CVF (Dohrenwend et al., 1986), suggesting that the polar cones have eroded much more gradually and less overall than the non-polar cones.

The degradation rate of the SFVF is more similar to that of the EVP (with all 9

Ma of data) than any other trend. Cones in both areas were emplaced in a hotspot/partially extensional setting, and there may be geochemical similarities between the erupted material. Initial cone dimensions in the SFVF are significantly larger than 119 those in the EVP. The EVP is largely a volcano cone field, whereas the SFVF is a platform field. The differences in topographic/surface setting and similarities in tectonic setting may imply that geochemical factors play an important role in dictating rates of erosion. However, there are not currently enough data to confidently limit the controlling factors.

There is a distinct difference between cones developed in hotspot settings and those developed in rifting and backarc extensional settings. MGVF, PPBF, SVF, and

CVF cones have initially higher initial H/WB values (0.17-0.20 compared to the 0.14-0.15 of the EVP and SFVF) and steeper and more pronounced degradation trends (i.e. between

19% and 129% higher decay constants). Most of this variation is likely due to weathering and not to tectonic setting, but the higher initial H/WB values indicate some degree of difference in conditions at formation.

120

0.25 SVF PPBF CVF 0.2 SFVF MGVF EVP with 3 Ma of data 0.15

EVP with 5 Ma of data

EVP with 9 Ma of data H/W

0.1

0.05

0 0 1 2 3 4 5 6 7 8 9 Cone Age (Ma)

Figure 54. A plot showing the H/WB degradation curves of the Erebus Volcanic Province and comparable cinder cone volcanic fields. The time period for which data is available is represented by a solid line; a dashed line signifies a time period over which the trend is extrapolated

Starting slopes estimated for the EVP cones are more similar to the Michoacán-

Guanajuato Volcanic Field than to the San Francisco Volcanic Field. Initial slopes estimated for polar cones and cones in the MGVF range from 22 to 24 degrees, whereas initial slopes estimated for the SFVF, which had the H/WB values most similar to the

EVP, are lower (Figure 55). However, the MGVF degraded much more quickly, reaching a slope of 2º after 9 Ma, compared with the SFVF’s 4º and EVP’s 16º. The degradation trend of the SFVF is therefore still the closest to parallel to that of the EVP, although the values are different. If only 3 Ma of EVP data are considered, equivalent to the record for

121 the SFVF, the parallel is even more apparent, suggesting again that these two systems share common characteristics.

The EVP data show higher decay constants and steeper curves of degradation with time using shorter periods of data; however, the polar trends are still 81 – 96% flatter than those derived for cone degradation in more temperate environments. These results further document the observation that polar cones do not erode as quickly or as intensely as non-polar cones.

30 SVF SFVF MGVF 25 EVP with 3 Ma of data EVP with 5 Ma of data EVP with 9 Ma of data

15 Slope (º) Slope

0 0 1 2 3 4 5 6 7 8 9 Cone Age (Ma)

Figure 55. A plot showing the slope degradation curves of the Erebus Volcanic Province and comparable cinder cone volcanic fields

122

The relatively slow and gradual erosion of polar versus non-polar cinder cones may be due to a variety of factors. One dominant factor is that there is little to no surface water activity on the surfaces of polar cones. Water is a driving force behind cinder cone erosion and surface irregularity in temperate volcanic fields (e.g. Wood, 1980; Karátson et al., 1999; Johnsen et al., 2010; Dóniz et al., 2011). Higher slopes on cinder cones result in higher-energy water flow, which in turn transports more water and material away from the steeper slopes faster. As the slopes shallow over time, the energy of the water decreases and moves over shallower slopes and larger surface areas, and the rate of erosion decreases (e.g. Dohrenwend et al., 1986). A lack of this particular driver of erosion would therefore result in a more linear, rather than exponential, trend through time like the one seen for EVP data in Figure 54 and Figure 55.

The lack of a distinct increase in irregularity index with time (Figure 39) also points to a lack of influence by water. Even in arid non-polar environments, brief, intense rains are main factors in the process of eroding cone flanks by means of gullying

(Johnsen et al., 2010; Dóniz et al., 2011), which carves meter-scale rills and gullies in the sides of cones, and non-channelized flow (Hooper, 1999). Lack of a systematic increase in irregularity index with time in the EVP as compared with non-polar fields indicates that this process does not play a role in cone erosion in the EVP.

Atkins and Dunbar (2009) note that the persistence, speed, and high density of cold wind play a powerful role in erosion processes in polar regions. Fornaciai et al.

(2010) indicate that frequent gale-force winds (90+ km/h) are a major contributor to cinder cone erosion at high altitudes on Mt. Etna. Ferreira and Fino (2012) demonstrated

123 on ridge models of coarse to medium sand with H/WB = 0.2 and 0.17 that wind abrades the tops of topographic highs. However, it tends not to significantly affect the upwind side, depositing material from the crest into a “recirculation bubble” on the downwind side. This recirculation bubble maintains the steepness of the slope over short time scales and causes slower erosion than water over time because of its relatively selective spatial influence.

Song et al. (2005) note that angularity of grains and moisture content are positively correlated with the shear strength of material. Because of the lack of surface- water interactions, grain smoothing is presumed to be absent on EVP cones (e.g. Cooper et al., 2007). The angularity of particles combined with potential cohesion of particles due to ice would result in high shear strength for the cones. This characteristic also limits erosion speed.

Wind plays a lesser role in the erosion of temperate and even subantarctic cones

(e.g. Holness, 2004) because of the effects of vegetation on surface roughness (Stockton and Gillette, 2006) and lower wind density in warmer environments. However, Greeley and Iversen (1987) determined that wind shear over lava and cinder cone surfaces in the

Mojave Desert can be 21% higher than over adjacent surfaces. Increased wind density due to colder temperatures in Antarctica may therefore have a substantial effect on the erosion of polar cones. However, few quantitative data exist describing the motion thresholds associated with basaltic scoria. Hooper (1999) monitored marked scoria on cone slopes in the San Francisco Volcanic Field, and Greeley and Iversen (1987) set up three 15-m towers with five anemometers each to measure wind velocity and direction

124 profiles around a cinder cone in the Mojave Desert. Long term study combining aspects of these studies would go far in definitively establishing wind erosion as a significant force.

Gravity, coupled with other factors such as freeze-thaw cycles, wind, sediment accumulation, and bioturbation, exerts influence on the erosion of cones (e.g Gabet,

2003; Holness, 2004). In the subantarctic islands and in other polar to subpolar regions

(e.g. Alaska), permafrost and freeze-thaw cycles in the active layer contribute to slow and fast mass movement activity, including solifluction and debris slides, especially in volcanic sediment partially weathered to clay (Holness, 2004). Studies from the Dry

Valleys region indicate that permafrost depth extends below 1.5 m and the active layer may be up to 75 cm thick (Bockheim et al., 2007). Water availability and temperature cycles in the EVP are such that thawing and refreezing may only take place over a very small fraction of the year, if it occurs at all. Therefore, freeze-thaw cycles are unlikely to play a significant role in cone erosion. However, cohesion of grains within permafrost may serve to help preserve cones by preventing erosion by other environmental factors.

Ice-cemented permafrost may contribute to the preservation of cones on Minna Bluff, where it is pervasive (Bockheim et al., 2007) and may have varied effects elsewhere in the EVP, as both ice-cemented (permafrosted) and unconsolidated cones have been observed in the field (T. Wilson, pers. comm., 2015).

Liquid water and more common phase changes between ice and water may have played a more significant role in cinder cone erosion in the past than they do now, e.g. prior to the Pliocene shift into persistent cold-based conditions ~3.4 Ma (Levy et al.,

125

2012). A higher spatial resolution of cone age data would be necessary to determine whether a distinct change in degradation rates can be identified at key climatic change boundaries since the Miocene.

Figure 56. A reconnaissance map of the Dry Valleys and EVP showing permafrost distribution by form (from Bockheim et al., 2007, Figure 2)

126

Sediment accumulation and mass wasting can both contribute to dry ravel, which is described by Gabet (2003) as a general term for downslope motion of particles via rolling, sliding, or bouncing. It can be a dominant, persistent form of erosion in steep and arid environments with little to no ground cover. Because this is a general term for a nonlinear concept of erosion, it is very difficult to quantitatively assign a portion of cone degradation to the process. Dry ravel can be induced by animal activity, ice dynamics

(e.g. Ballantyne, 1991; Lawler, 1993), sediment loading, or oversteepening of supporting material (e.g. retrogressive thaw slumps). Given these factors, dry ravel probably plays some role in EVP cinder cone erosion, but would be expected to vary with climate factors through time.

Cone structure and morphology also relate directly to erodibility. Cones that consist of more welded material may also erode more slowly than those comprised of primarily loose, unconsolidated grains (Dohrenwend et al., 1986; Valentine et al., 2006).

Scott and Trask (1971) and Settle (1979) also suggest that smaller cones erode faster via fluvial processes because the ratio of surface area to volume increases with decreasing cone diameter, thereby exposing a larger fraction of particles to surface erosive processes on smaller cones. In the EVP, an environment with little precipitation influence, cones of variable size may erode at more uniform rates. More systematic analysis of age- constrained cones differentiated by size would be necessary to test this further.

Initial and post-eruption (erosion-related) morphology, including cone size and particle cohesion (and consequent erosion resistance), is partially dependent upon geochemistry (Kervyn et al., 2012). Certain lava compositions may erode faster or may

127 retain cohesion for longer. Few examples exist in the literature about erosion of mafic composition materials, but Pye (1986) found that potassium-rich granitoid rocks are more resistant to erosion than potassium-poor rocks, and that the presence of Ca-rich plagioclase implies lower resistance. Jiménez-Espinosa et al. (2007) similarly noted that high plagioclase and kaolinite content, mineral hydration, and lower Si/Al ratios contribute to expedited weathering in granitic materials. General geochemical profiles have been compiled for different eruptive centers in the EVP (e.g. Kyle, 1990a), and in some areas detailed geochemistry of sampled cones has been published (e.g. Minna

Bluff; Wilch et al., 2008l; Panter et al., 2011). However, not enough detailed geochemical analysis of individual cones in the EVP has been performed to be able to compare and contrast cone geochemistry to determine systematic trends in composition versus erosion characteristics.

The Effect of Cold-Based Glaciation on Cone Morphology

Given the lack of ice sheet and glacial models of high spatial resolution (i.e. less than 5 km) in the Ross Sea Region, it is impossible to project ice sheet extents over the

Miocene and Pliocene to the degree of precision necessary to determine whether, and how often, individual EVP cinder cones were overrun by ice. The Last Glacial Maximum reconstructed ice sheet footprint of Denton and Marchant (2000) and Denton and Hughes

(2000) remains the only well-constrained, high-resolution reconstruction for the

McMurdo Sound region.

128

McKay et al. (2009) and Levy et al. (2012) argue that modern climate conditions, including cool temperatures, obliquity-paced glacial cycles, and a semi-permanent sea-ice fringe, have persisted since the late Pliocene/early Pleistocene. To evaluate the effects of glacial erosion on scoria cone morphologic change, this study assumes that maximum glacial extents over the course of the Pleistocene have been the same as at the LGM.

Thus cones that were older than and covered by the ice sheet at the LGM were likely covered previously and old cones that were not covered at the LGM have not been covered since their formation. This assumption is likely to be flawed: ice nucleation points and flow paths shifted during and after the emergence of Mt. Erebus, Mt. Terror, and Hut Point (Figure 57; Talarico et al., 2012) and changes in ice sheet dynamics may have created thicker ice in some areas in the early Pleistocene than in the later

Pleistocene. The possibility therefore exists that some cones that were not covered in the

LGM may have been under grounded ice during previous Pleistocene glaciations. By comparing the subset of studied cones only formed during the Pleistocene, I have attempted to eliminate the complications created by the influence of changing paleotopography on ice sheet dynamics and footprint.

129

Figure 57. Reconstructed pathways for ice into the Ross Sea during glacial expansion in the Late Pleistocene (A) and in the Pliocene (B) (modified from Talarico et al., 2012, Figure 6)

It is well established that wet-based glaciers erode their substrate (e.g. Sugden et al., 2005). The interactions between the surface and cold-based glaciers are, however, less clear. This study aimed to look beyond the small-scale abrasive and depositional features studied by previous authors (e.g. Fitzsimons et al., 2000; Lloyd-Davies et al.,

130

2009; Atkins, 2011) to determine whether large-scale morphology is noticeably affected by the presence and overriding motion of cold-based glaciers. Because of the climate conditions during the Pleistocene (McKay et al., 2009; Levy et al., 2012), it is assumed that glaciation in the Ross Sea region has been limited to a dry-based, frozen-bed regime.

No definitive differences are evident between Pleistocene cones that were glaciated during the LGM (and presumably prior to that, for older cones) and those that were not, even when consolidating cones into age-grouped averages. The slight difference between initial H/WB values (Figure 42A) perhaps hints at some degree of preservation of cones that have been covered by cold-based glaciers; however, the crossover of the glaciated and nonglaciated trends around 1.5 Ma, along with the low R2 values, suggest that the apparent trends are a result of too few data with a high level of scatter. The highest (0.22 on Hut Point) and lowest (0.087 in the RSR) H/WB values belong to glaciated cones, and where there are cones from both groups with very similar ages, H/WB values of non-glaciated cones are not systematically lower or higher than those of glaciated cones.

The averaged H/WB groups plot (Figure 42B) shows that average values for non- glaciated Early Pleistocene cones are higher than those for glaciated cones. Conversely, both earliest Pleistocene and Middle-Late Pleistocene groups have higher average H/WB values for glaciated cones. Slope trends (Figure 43) do not correlate with H/WB trends: the slope of non-glaciated cones decreases at a rate faster than that for glaciated cones, whereas the H/WB of glaciated cones decreases at a rate faster than for non-glaciated cones.

131

The H/WB trends indicate that glaciated cones are eroded faster than non- glaciated cones. STOT trends that incorporate age and slope error reflect the same regime, while STOT trends that do not account for error indicate the opposite. It may be possible that the differential velocity column in the cold-based glacier (e.g. Waller, 2001; Figure

58) abraded the top of the cinder cones faster than the slopes and the base, thus enabling height to width ratio to decrease rapidly while the basal width and slope stay comparatively consistent. Additional work is necessary to determine whether this is a viable hypothesis. Conservative and approximate t-tests indicate that the error-cognizant slope trends are not statistically distinguishable from each other, indicating that there may not be a difference in morphology between cones that have been overridden by cold- based glaciers and those that have not.

Similar tests need to be performed on H/WB ratios when standard deviation data are available, and more cone morphology data from relevant age ranges are needed to determine whether more robust trends emerge. Field work would be needed to determine whether an erosion profile at the interface between the cone surface and the base of the glacier could be determined from geochronological, geochemical, and lithological evidence (e.g. Wilch et al., 2008).

132

Figure 58. A diagrammatic representation of the character of two different cold-based glacier flow velocity profiles. Each is slow moving and relies at least partly on creep as its primary sense of motion (modified from Waller, 2001, Figure 4)

Irregularity index, which over the Miocene time scale doesn’t reveal evident trends (Figure 39), shows an increase for Pleistocene cones with a surprisingly high R2 value of 0.6782 (Figure 59). Glaciated cones show a faster rate of increase in irregularity index than non-glaciated cones (Figure 59). Meltwater channels, as described by Atkins and Dickinson (2007) and Atkins (2013), are one possible mechanism that could increase the surface irregularity of glaciated cones, even for an overall cold-based ice sheet, and 133 would not be expected to exist on non-glaciated cones. It is not known, however, how erosion rates from meltwater channels beneath grounded ice would compare with erosion rates due to wind or other factors on non-glaciated cones during episodes of maximum glaciation.

2.5 Glaciated Non-glaciated 2 y = 1.0228e0.209x R² = 0.6782

1.5

1 y = 1.2023e0.1016x R² = 0.1332 0.5

0 0.000 0.500 1.000 1.500 2.000 2.500 3.000 Cone age (Ma)

Figure 59. A plot showing the trend of irregularity index relative to age of cones that were glaciated during the Pleistocene and those that were not

Cone Morphology as an Age Indicator in Polar Environments

The shape of cinder cones, despite their relative geomorphological homogeneity, is still affected by numerous variables both during their formation and subsequent degradation. Geochemistry, tectonic setting, preexisting topography, and other factors have important influences on high-resolution features of cone morphology (e.g.

Kereszturi et al., 2012; Kervyn et al., 2012; Figure 60). The substantial scatter in plots of 134 morphological parameters vs. time for EVP cones reflects such influences, and data is currently insufficient to control for the range of factors. Using well-constrained dating and average values for groups of cones, however, appears to have much stronger potential to demonstrate systematic changes in morphology over time (e.g. Dohrenwend et al., 1986; Hoffer et al., 1998; Favilli et al., 2009; Bemis et al., 2011; Kervyn et al.,

2012).

Figure 60. A schematic illustration showing cinder cone morphology and structures with lateral variation in deposits, slope angles, and other factors affecting commonly used morphometric ratios (from Kervyn et al., 2012)

Plots of morphologic parameters vs. age show the wide range of scatter for individual cones and the strong trends that emerge by plotting values averaged by geological age. Each time-averaged group of cones has wide-ranging maximum and minimum values for morphological parameters (Table 8).

135

Table 8. Morphological parameters and statistics for cones grouped in geological time windows

Mean H/WB Mean STOT Age Group Cones Min Max Avg σ % in 1σ Min Max Avg σ % in 1σ Middle Pleistocene to Present 8 0.11 0.23 0.15 0.042 63 20.0 30.5 23.5 3.70 75 Early Pleistocene 13 0.09 0.19 0.13 0.032 62 15.7 25.3 20.8 3.15 54 Pliocene 8 0.06 0.14 0.10 0.021 78 13.0 22.8 18.5 3.21 56 Miocene 5 0.03 0.11 0.08 0.029 57 15.8 19.9 17.9 1.60 43 σ = standard deviation of the group, and % in 1σ denotes the percentage of cones in the group that fall within one standard deviation

2 Trends plotted for age group-averaged values of STOT and H/WB have R values of

0.8351 and 0.9891, respectively, a vastly better correlation than the trends calculated for individual cone parameters (0.2417 and 0.4433, respectively). This does not, however, provide a straightforward improvement in the reliability of accurately placing an undated cone on a morphologically calibrated age scale. In the group of cones formed during the

Middle Pleistocene to present, the 8 cones showed an average STOT of 23.5° ± 3.70°, where the error represents one standard deviation, and 75% of the cones in this age group fall within one standard deviation. The 13 Early Pleistocene cones have an average slope of 20.8° ± 3.15°, with 54% of cones falling within one standard deviation—a substantial drop-off from the first group. This is indicative of an increasing degree of variability as cones age and, presumably, more processes have altered their morphology. 56% of

Pliocene cones and only 43% of Miocene cones fall within one standard deviation of the mean.

As Table 8 and Figure 61 show, there is significant overlap in parameter values between age groups. The overlap is in all cases more than one standard deviation, i.e. every averaged value lies within one standard deviation of the averaged value for the previous (younger) age group. Thus a cone of unknown age, if parameterized, could not 136 be confidently placed within any one group. For example, if a cone was determined to have a mean total slope of 21°, it may be a member of any except the Miocene group.

Any cone parameterized within the values of the Miocene group could also fall in the

Pliocene group.

35.00 PL2 PL1 P M

30.00 y = 22.591e-0.036x R² = 0.8351

25.00

º)

(

TOT S 20.00

15.00

10.00 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Cone age (Ma)

Figure 61. A plot of age-averaged STOT values versus cone age, with vertical and horizontal error bars representing one standard deviation of the mean slope and ages within the group, respectively. Groups are delineated by vertical lines; M = Miocene (> 5.33 Ma), P = Pliocene (5.33 – 2.59 Ma), PL1 = Early Pleistocene (2.59 – 0.78 Ma), and PL2 = Middle Pleistocene to Present (< 0.78 Ma). The standard deviation range of the Miocene, within which 43% of cones fall, lies entirely within the standard deviation range of the Pliocene; the other age groups have some values within one standard deviation that do not overlap with yet other age groups, providing a means to potentially estimate the age of a morphologically parameterized cone within a few million years.

The H/WB values show similar uncertainties, although they overlap less than slope values (Figure 62). Unlike Kereszturi et al. (2013), who found slope angle to be the most reliable age indicator of cones on volcano slopes at Bandas del Sur, this study finds

137

H/WB to be more reliable. Plotted individual and grouped values show the highest correlation coefficients of any measured parameter. Additionally, instead of having up to

100% overlap between adjacent age groups (e.g. Pliocene and Miocene cone slope values), H/WB values show a maximum overlap between one group and the next of 62%, between the Middle Pleistocene – Present and Early Pleistocene groups. This indicates a stronger likelihood that a cone with a given H/WB would fall within only one or two possible age groups, rather than the three age groups that STOT yielded. 63% of Middle

Pleistocene – Present cones fall within one standard deviation of mean H/WB values—a slight decrease relative to slope statistics—but there is an improvement for the three remaining age groups: 62% of Early Pleistocene cones fall within one standard deviation of the mean; 78% of Pliocene cones; and 57% of Miocene cones.

138

0.250

PL2 PL1 P M

0.200 y = 0.1507e-0.087x R² = 0.9891

0.150

B H/W 0.100

0.050

0.000 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Cone age (Ma)

Figure 62. A plot of age group-averaged cone H/WB values versus age, with the vertical and horizontal error bars representing one standard deviation of the mean height to width ratio and ages within the groups, respectively. Vertical lines delineate the age groups, which are classified as in Figure 61

These results show that topography-scale morphologic parameters of cinder cones can be used as age indicators over long time scales (e.g. millions of years, epoch-scale), but that they are significantly less reliable over short time scales. All cones from this study with a H/WB greater than 0.15 and a slope greater than 23º are Quaternary in age

(Figure 63), so any undated cones with parameters that fit this description are likely

Quaternary also. This can be further narrowed, because all cones with H/WB > 0.19 and

STOT > 26º are Late Pleistocene to Holocene in age. All studied cones with STOT > 16º are

Miocene in age, but a similar Miocene upper bracket for H/WB does not exist, as some

Pliocene cones have very low H/WB values. Cones with slope values less than 19º and

H/WB less than 0.08 can be assigned to the Pliocene or Miocene, but resolving them

139 beyond that is difficult because, as Figure 63 shows, no group of cones except the end members (Pleistocene – Recent and Miocene) has a range which is in whole or in part unique.

0.26 32 30 0.21 28 26

0.16 24

º) (

TOT H/W 0.11 20 S 18 0.06 16 14 0.01 12 0.0 2.0 4.0 6.0 8.0 10.0 Cone age (Ma)

Figure 63. A plot showing, side-by-side, the trends and distributions of both individually plotted and age group-averaged H/WB (left y axis, blue) and STOT (right y axis, orange) values versus cones age

Because of the wide variability of parameters between cone fields (see Variation in cone dimensions), absolute age cannot be assigned to one volcanic cone province based on cone morphology parameters established in a different province. As this and previous studies have shown and discussed, cones in different tectonic and environmental settings erode at different rates. They may still go through the same morphological stages of erosion, but with differing degrees of intensity and/or over different time spans. For example, due to lack of fluvial erosion, cones in the EVP may have a longer topographic

140 lifespan than cones in more temperate fields. Cones that consist of more welded material may also erode more slowly than those comprised of primarily loose, unconsolidated grains. In both these instances, the older cones may have the same slopes or H/WB as younger ones from a different field, but due to their rheologic or environmental properties, they have been better preserved at a more advanced age. It is also feasible that, in glaciated environments or temperate ones, cones have a maximum lifespan as a landform and may be completely eroded to the point where no indicators of its existence remain except for detrital sediment. Some volcanic features on slopes in Wright and

Taylor Valleys show low, central peaks surrounded by extremely shallow slopes that hint at a previously conical shape (Figure 64). Because of their current morphology, they can’t unambiguously be identified as cinder cones. Until we have a better understanding of the environmental and geologic factors that affect cone formation and degradation, determining absolute age from cones in multiple, geographically disparate regions will not be effective.

141

Figure 64. An orthophoto, slope map, and profiles of a volcanic feature in Taylor Valley that shows possible remnants of cone and crater morphology. The NW – SE Profile shows what looks like a flattened cross-section of a cone crater and both profiles reflect traces of a conical feature

Summary

Cinder cone morphology, generally considered to be uniform at the time of formation, is in fact influenced by a range of factors both during eruption and during post-emplacement degradation. From a process viewpoint, not all of syn-eruptive and erosional factors are well understood. It is clear, however, that there is ubiquitous, 142 systematic change with time in slope and height-to-width ratios of cinder cones in the polar desert environment of the EVP. Degradation processes are slower and more linear in the EVP than in temperate, arid, or semiarid volcanic fields, reflecting the diminished role of liquid water. A lack of systematic increase in surface irregularity with time also points to limited surface water relative even to desert environments at lower latitudes, where rills and gullies develop as a result of sporadic rainfall (Johnsen et al., 2010).

In place of water, wind activity may play a primary role in cone degradation since the shift to persistent polar desert conditions in Antarctica. Consistent cold wind at high velocities has significant abrading power (Atkins and Dunbar, 2009), especially over volcanic surfaces with high surface roughness (Greeley and Iverson, 1987). Additional quantitative data on motion thresholds associated with basaltic scoria, as well as detailed analysis of local wind vectors and possibly paleo wind data, are needed to fully evaluate and quantify the effect of wind on volcanic surfaces in the EVP. Freeze-thaw cycles, needle ice, and melting or sublimating permafrost are effective at dislodging unconsolidated material on slopes, but given the low water budget and the possibility that the terrestrial environment of the EVP region has been relatively stable since the mid-

Miocene (e.g. Sugden and Denton, 2004), it is unlikely that these are prominent erosion processes on EVP cones. Long-lived, ice-cemented permafrost (Bockheim et al., 2007) may, in fact, aid in the preservation of old cones in areas such as Minna Bluff. Subsurface ice leaves distinct, small-scale topographic features (e.g. Dickinson and Rosen, 2003) and future work to determine if these occur on EVP cones could determine whether and to what extent these processes are actually occurring.

143

The role of cold-based glaciers in cinder cone erosion is unclear. Wide scatter in morphometric parameters and opposing slope and height/width trends are present for glaciated vs nonglaciated cones. According to the data collected, H/WB decrease occurs more quickly on glaciated cones than on non-glaciated ones, whereas STOT decreases more quickly on non-glaciated cones. These apparently opposite trends may be attributable to the differential velocity column in cold-based glaciers abrading the tops of cinder cones faster than the slopes and base; however, given the scarcity and scatter of data, it is also possible that the trends are just poorly constrained. More data are needed to establish whether the trends established by this study are robust.

Irregularity index, which over large time scales in the EVP doesn’t show a definitive trend, does show on increase on glaciated cones by a factor of 2 relative to non- glaciated cones over the course of the Pleistocene. Atkins and Dickinson (2007) describe subglacial meltwater channels as potential mechanisms for surface modification, even in polar ice environments. However, a better understanding of how erosion rates compare between this and processes affecting exposed surfaces (e.g. wind) is necessary to facilitate comparison.

The strong variability of morphometric parameters for individual cinder cones of similar age results in data scatter that makes assigning precise absolute ages difficult. A more complete understanding of the factors that affect cone degradation, e.g. geochemistry, tectonic setting, existing topography, high spatial resolution of wind and precipitation patterns, may help account for the variability, but data is currently insufficient to effectively calibrate morphologic change for single cones. The results

144 presented here show instead that topography-scale morphologic parameters can be used as age indicators over long, epoch-scale time scales. R2 values for age-averaged groups are significantly higher than for individually plotted cones, and H/WB shows a better correlated trend and less overlap between age groups than STOT, contrary to some previous studies (e.g. Kereszturi et al., 2013).

Because of variability in both syn-eruptive and environmentally-controlled degradation processes between volcanic cone fields, the results reported here are not directly applicable to cone fields outside the EVP. Cones in different tectonic and environmental settings erode at different rates and with differing profiles (i.e. linear versus exponential). Water, wind, and other erosive forces have unique signatures that imprint on erosion rates and profiles in different environments. Until we have a more comprehensive understanding of the various factors that affect cone formation and degradation, using an age-calibrated morphologic trend for cones from one region to determine absolute age of cones in other, geographically disparate regions, will not be effective. However, this and past research shows that morphologic change due to cone erosion is time dependent and, to some degree, predictable. As our understanding of the processes producing variability in cone formation and degradation increases, we can use and calibrate morphologic trends to apply cone morphology as an analysis method for geochronology and structural analysis to regions where remote sensing is currently the only viable means of procuring data, and as a means of corroboration in areas where groundwork is possible.

145

References

Armstrong, R.L., 1978, K-Ar dating: Late Cenezoic McMurdo Volcanic Group and Dry Valley glacial history, Victoria Land, Antarctica: New Zealand Journal of Geology and Geophysics, v. 21, p. 685-698.

Atkins, C.B., 2013, Geomorphological evidence of cold-based glacier activity in South Victoria Land, Antarctica: Geological Society of London Special Publications, v. 381, p. 299-318.

Atkins, C.B., and Dickinson, W.W., 2007, Landscape modification by meltwater channels at margins of cold-based glaciers, Dry Valleys, Antarctica: Boreas, v. 36, p. 47-55.

Atkins, C. B., Dickinson, W., Joy, K. and Storey, B., 2011, Influence of cold-based glaciers on landscape development, in Proceedings, 11th International Symposium on Antarctic Earth Sciences, Edinburgh: Scientific Committee on Antarctic Research, p. 168.

Atkins, C.B., and Dunbar, G.B., 2009, Aeolian sediment flux from sea ice into Southern McMurdo Sound, Antarctica: Global and Planetary Change, v. 69, p. 133-141.

Ballantyne, C.K., 1991, Holocene geomorphic activity in the Scottish Highlands: Scottish Geographical Magazine, v. 107, p. 84-98.

Bamber, J.L., Griggs, J.A., Hurkmans, R.T.W.L., Dowdeswell, J.A., Gogineni, S.P., Howat, I., Mouginot, J., Paden, J., Palmer, S., Rignot, E., and Steinhage, D., 2013, A new bed elevation dataset for Greenland: The Cryosphere, v. 7, p. 499-510.

Bannister, S., Yu, J., Leitner, B., and Kennett, B.L.N., 2003, Variations in crustal structure across the transition from West to East Antarctica, Southern Victoria Land: Geophysical Journal International, v. 155, p. 870-884.

Bemis, K., Walker, J., Borgia, A., Turrin, B., Neri, M., and Swisher, C., 2011, The growth and erosion of cinder cones in Guatemala and El Salvador: models and statistics: Journal of Volcanology and Geothermal Research, v. 201, p. 39-52.

146

Bierman, P.R., Corbett, L.B., Graly, J.A., Neumann, T.A., Lini, A., Crosby, B.T., and Rood, D.H., 2014, Preservation of a preglacial landscape under the center of the Greenland ice sheet: Science, v. 344, p. 402-405.

Bleacher, J.E., Glaze, L.S., Greeley, R., Hauber, E., Baloga, S.M., Sakimoto, S., Williams, D.A., and Glotch, T.D., 2009, Spatial and alignment analyses for a field of small volcanic vents south of Pavonis Mons and implications for the Tharsis province, Mars: Journal of Volcanology and Geothermal Research, v. 185, p. 96-102.

Bloomfield, K., 1975, A late-Quaternary monogenetic volcano field in central Mexico: Geologische Rundschau, v. 64, p. 476-497.

Bockheim, J.G., Campbell, I.B., and McLeod, M., 2007, Permafrost distribution and active-layer depths in the McMurdo Dry Valleys, Antarctica: Permafrost and Periglacial Processes, v. 18, p. 217-227.

Carracedo, J.C., Badiola, E.R., and Soler, V., 1992, The 1730-1736 eruption of Lanzarote, Canary Islands – A long, high magnitude basaltic fissure eruption: Journal of Volcanology and Geothermal Research, v. 53, p. 239-250.

Clarke, H., Troll, V.R., and Carracedo, J.C., 2009, Phreatomagmatic to Strombolian eruptive activity of basaltic cinder cones: Montaña Los Erales, Tenerife, Canary Islands: Journal of Volcanology and Geothermal Research, v. 180, p. 225-245.

Cohen, K.M., Finney, S.C., Gibbard, P.L., and Fan, J.-X., 2013 (updated), The ICS international chronostratigraphic chart: Episodes, v. 36, p. 199-204.

Conner, C.B., 1990, Cinder cone clustering in the TransMexican Volcanic Belt: implications for structural and petrologic models: Journal of Geophysical Research, v. 95, p. 19,395-19,405.

Connor, C.B., Condit, C.D., Crumpler, L.S., and Aubele, J.C., 1992, Evidence of regional structural controls on vent distribution: Springerville Volcanic Field, Arizona: Journal of Geophysical Research, v. 97, p. 12,349-12,359.

Cooper, A.F., Adam, L.J., Coulter, R.F., Eby, G.N., and McIntosh, W.C., 2007, Geology, geochronology and geochemistry of a basanitic volcano, White Island, Ross Sea, Antarctica: Journal of Volcanology and Geothermal Research, v. 165, p. 189-216.

Corazzato, C., and Tibaldi, A., 2006, Fracture control on type, morphology and distribution of parasitic volcanic cones: an example from Mt. Etna, Italy: Journal of Volcanology and Geothermal Research, v. 158, p. 177-194.

147

Cowan, E.A., Seramur, K.C., Cai, J., and Powell, R.D., 1999, Cyclic sedimentation produced by fluctuations in meltwater discharge, tides, and marine productivity in an Alaskan fjord: Sedimentology, v. 46, p. 1109-1126.

Csathó, B., Schenk, T., Krabill, W., Wilson, T., Lyons, W., McKenzie, G., Hallam, C., Manizade, S., and Paulsen, T., 2005, Airborne laser scanning for high-resolution mapping of Antarctica: Eos, v. 86, no. 25, p. 237-238.

Cuffey, K.M., Conway, H., Gades, A.M., Hallet, B., Lorrain, R., Severinghaus, J.P., Steig, E.J., Vaughn, B., and White, J.W.C., 2000, Entrainment at cold glacier beds: Geology, v. 28, p. 351-354.

Cziferszky, A., Fleming, A.H., and Fox, A., 2010, An assessment of ASTER elevation data over glaciated terrain on Pourquis Pas Island, Antarctic Peninsula: Geological Society of London Special Publications, v. 345, p. 23-32.

Davis, P.T., Briner, J.P., Coulthard, R.D., Finkel, R.W., and Miller, G.H., 2006, Preservation of Arctic landscapes overridden by cold-based ice sheets: Quaternary Research, v. 65, p. 156-163.

De Santis, L., Anderson, J.B., Barncolini, G., and Zayatz, I., 1995, Seismic record of late Oligocene through Miocene glaciation in the central and eastern continental shelf of the Ross Sea, in Cooper, A.K., et al., eds., Geology and Seismic Stratigraphy of the Antarctic Margin: Washington, D.C., American Geophysical Union, Antarctic Research Series, v. 68, p. 235-260.

Del Carlo, P., Panter, K.S., Bassett, K., Bracciali, L., Di Vincenzo, G., and Rocchi, S., 2009, The upper lithostratigraphic unit of ANDRILL AND-2A core (Southern McMurdo Sound, Antarctica): Local Pleistocene volcanic sources, paleoenvironmental implications and subsidence in the southern Victoria Land Basin: Global and Planetary Change, v. 69, p. 142-161.

Denton, G.H., and Hughes, T.J., 2000, Reconstruction of the Ross ice drainage system, Antarctica, at the Last Glacial Maximum: Geografiska Annaler, v. 82, p. 143-166.

Denton, G.H., and Marchant, D.R., 2000, The geologic basis for a reconstruction of a grounded ice sheet in McMurdo Sound, Antarctica, at the Last Glacial Maximum: Geografiska Annaler, v. 82, p. 167-211.

Denton, G.H., Sugden, D.E., Marchant, D.R., Hall, B.L., and Wilch, T.I., 1993, East Antarctic Ice Sheet sensitivity to Pliocene climatic change from a Dry Valleys perspective: Geografiska Annaler, v. 75, p. 155-204.

148

Derrick, T.R., Bates, B.T., and Dufek, J.S., 1994, Evaluation of time-series data sets using the Pearson product-moment correlation coefficient: Medicine and Science in Sports and Exercise, v. 26, p. 919-928.

Di Traglia, F., Cimarelli, C., de Rita, D., and Torrente, D.G., 2009, Changing eruptive styles in basaltic explosive volcanism: examples from Croscat complex scoria cone, Garrotxa Volcanic Field (NE Iberian Peninsula): Journal of Volcanology and Geothermal Research, v. 180, p. 89-109.

Di Vincenzo, G., Bracciali, L., Del Carlo, P., Panter, K., Rocchi, S., 2010, 40Ar–39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): correlations with the Erebus Volcanic Province and implications for the age model of the core: Bulletin of Volcanology, v. 71, p. 487-505.

Dohrenwend, J.C., 1987, Morphologic criteria for estimating the ages of quaternary basaltic cinder cones, in Proceedings, Hawaii Symposium on How Volcanoes Work, Hilo, HI: Hawaii Institute of Geophysics, p. 56.

Dohrenwend, J.C., Wells, S.G., and Turrin, B.D., 1986, Degradation of Quaternary cinder cones in the Cima volcanic field, Mojave Desert, California: Geological Society of America Bulletin, v. 97, p. 421-427.

Domack, E., Duran, D., Leventer, A., Ishman, S., Doane, S., McCallum, S., Amblas, D., Ring, J., Gilbert, R., and Prentice, M., 2005, Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch: Nature, v. 436, p. 681-685.

Dóniz, J., Romero, C., Carmona, J., and García, A., 2011, Erosion of Cinder Cones in Tenerife by Gully Formation, Canary Islands, Spain: Physical Geography, v. 32, p. 139-160.

Echelmeyer, K. and Zhongxiang, W., 1987, Direct observation of basal sliding and deformation at sub-freezing temperatures: Journal of Glaciology, v. 33, p. 83–98.

Elliot, D.H., 1992, Jurassic magmatism and tectonism associated with Gondwanaland break-up: an Antarctic perspective: Geological Society of London Special Publications, v. 68, p. 165-184.

Esser, R.P., Kyle, P.R., and McIntosh, W.C., 2004, 40Ar/39Ar dating of the eruptive history of Mount Erebus, Antarctica: volcano evolution: Bulletin of Volcanology, v. 66, p. 671-686.

149

Euillades, L.D., Grosse, P., and Euillades, P.A., 2013, NETVOLC: an algorithm for automatic delimitation of volcano edifice boundaries using DEMs: Computers & Geosciences, v. 56, p. 151-160.

Favalli, M., Karátson, D., Mazzarinin, F., Pareschi, M.T., and Boschi, E., 2009, Morphometry of scoria cones located on a volcano flank: a case study from Mt. Etna (Italy), based on high-resolution LiDAR data: Journal of Volcanology and Geothermal Research, v. 186, p. 320-330.

Fedorov, A.V., Brierley, C.M., and Emanuel, K., 2010, Tropical cyclones and permanent El Nino in the early Pliocene epoch: Nature, v. 463, p. 1066-1077.

Ferreira, A.D., and Fino, M.R.M., 2012, A wind tunnel study of wind erosion and profile reshaping of transverse sand piles in tandem: Geomorphology, v. 139-140, p. 230- 241.

Fielding, C.R., Browne, G.H., Field, B., Florindo, F., Harwood, D.M., Krissek, L.A., Levy, R.H., Panter, K.S., Passchier, S., and Pekar, S.F., 2011, Sequence stratigraphy of the ANDRILL AND-2A drillcore, Antarctica: a long-term, ice-proximal record of Early to Mid-Miocene climate, sea-level and glacial dynamism: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 305, p. 337-351.

Fielding, C.R., Henrys, S.A., and Wilson, T.J., 2006, Rift history of the Western Victoria Land Basin: a new perspective based on integration of cores with seismic reflection data, in Futterer, D.K., Damaske, D., Kleinschmidt, G., Miller, H., and Tessensohn, F., eds., Antarctica: contributions to global earth sciences: Berlin, Springer-Verlag, p. 309-318.

Fitzgerald, P., 2002, Tectonics and the landscape evolution of the Antarctic plate since the breakup of Gondwana, with an emphasis on the West Antarctic Rift System and the Transantarctic Mountains: Royal Society of New Zealand Bulletin, v. 35, p. 453- 469.

Fitzgerald, P.G., Saniford, M., Barrett, P.J., and Gleadow, A.J.W., 1986, Asymmetric extension associated with uplift and subsidence in the Transantarctic Mountains and Ross Embayment: Earth and Planetary Science Letters, v. 81, p. 67-78.

Fitzsimons, S.J., McManus, K.J., Lorrain, R.D., 1999, Structure and strength of basal ice and substrate of a dry-based glacier: evidence for substrate deformation at subfreezing temperatres: Annals of Glaciology, v. 28, p. 236-240.

Fitzsimons, S.J., Lorrain, R.D., and Vandergoes, M.J., 2000, Behaviour of subglacial sediment and basal ice in a cold glacier, in Maltman, A.J., Hubbard, B., and

150

Hambrey, M.J., eds., Deformation of Glacial Materials: Geological Society of London Special Publications, v. 176, p. 181-190.

Fornaciai, A., Favilli, M., Karatson, D., Tarquini, S., and Boschi, E., 2012, Morphometry of scoria cones, and their relation to geodynamic setting: A DEM-based analysis: Journal of Volcanology and Geothermal Research, v. 217-218, p. 56-72.

Gabet, E.J., 2003, Sediment transport by dry ravel: Journal of Geophysical Research, v. 108, Article 2049, 22 p.

Gleadow, A.J.W., and Fitzgerald, P.G., 1987, Uplift history and structure of the Transantarctic Mountains: new evidence from fission track dating of basement apatites in the Dry Valleys area, southern Victoria Land: Earth and Planetary Science Letters, v. 82, p. 1-14.

Goodfellow, B.W., 2007, Relict non-glacial surfaces in formerly glaciated landscapes: Earth-Science Reviews, v. 80, p. 47-73.

Greeley, R., and Iversen, J.D., 1987, Measurements of wind friction speeds over lava surfaces and assessment of sediment transport: Geophysical Research Letters, v. 14, p. 925-928.

Grosse, P., van Wyk de Vries, B., Petrinovic, I.A., Euillades, P.A., and Alvarado, G.E., 2009, Morphometry and evolution of arc volcanoes: Geology, v. 42, p. 651-654.

Grosse, P., van Wyk de Vries, B., Euillades, P.A., Kervyn, M., and Petrinovic, I.A., 2012, Systematic morphometric characterization of volcanic edifices using digital elevation models: Geomorphology, v. 136, p. 114-131.

Grosse, P., Euillades, P., Euillades, L., and van Wyk de Vries, B., 2014, A global database of composite volcano morphometry: Bulletin of Volcanology, v. 76, Article 784, 16 p.

Hall, J., Wilson, T., and Henrys, S., Structure of the central Terror Rift, western Ross Sea, Antarctica, in Cooper, A.K., and Raymond, C.R., eds., Proceedings, 10th ISAES: USGS Open-File Report 2007-1047, Short Research Paper 108, 5 p.

Hansen, S.E., Julià, J., Nyblade, A.A., Pyle, M.L., Weins, D.A., and Anandakrishnan, S., 2009, Using S wave receiver functions to estimate crustal structure beneath ice sheets: An application to the Transantarctic Mountains and East Antarctic craton: Geochemistry, Geophysics, Geosystems, v. 10, Article Q08014, 10 p.

151

Harpel, C.J., Kyle, P.R., Esser, R.P., McIntosh, W.C., and Caldwell, D.A., 2004, 40Ar/39Ar dating of the eruptive history of Mount Erebus, Antarctica: summit flows, tephra, and caldera collapse: Bulletin of Volcanology, v. 66, p. 687-702.

Hasenaka, T., and Carmichael, I.S.E., 1985, The cinder cones of Michoacán-Guanajuato, central Mexico: their age, volume and distribution, and magma discharge rate: Journal of Volcanology and Geothermal Research, v. 25, p. 105-124.

Hayakawa, Y., Oguchi, T., and Lin, Z., 2008, Comparison of new and existing global digital elevation models: ASTER G-DEM and SRTM-3: Geophysical Research Letters, v. 35, L17404, 5 p.

Head, J.W., and Wilson, L., 1989, Basaltic pyroclastic eruptions: influence of gas-release patterns and volume fluxes on fountain structure, and the formation of cinder cones, spatter cones, rootless flows, lava ponds, and lava flows: Journal of Volcanology and Geothermal Research, v. 37, p. 261-271.

Henrys, S., Wilson, T., Whittaker, J.M., Fielding, C., Hall, J., and Naish, T., 2007, Tectonic history of mid-Miocene to present southern Victoria Land Basin, inferred from seismic stratigraphy in McMurdo Sound, Antarctica, in Cooper, A.K., and Raymond, C.R., eds., Proceedings, 10th ISAES: USGS Open-File Report 2007-1047, Short Research Paper 049, 4 p.

Hodson, A.J., and Ferguson, R.I., 1999, Fluvial suspended sediment transport from cold and warm-based glaciers in Svalbard: Earth Surface Processes and Landforms, v. 24, p. 957-974.

Hoffer, J.M., Penn, B.S., Quezada, O.A., and Morales, M., 1998, Qualitative age relationships of Late Cenozoic cinder cones, southern Rio Grande Rift, utilizing cone morphology and LANDSAT thematic imagery: a preliminary assessment, in Mack, G.H., ed., Las Cruces Country II, 49th Field Conference: New Mexico Geological Society Guidebook, p. 123-128.

Holmlund, P., and Näslund, J.-O., 1994, The glacially sculptured landscape in Dronning Maud Land, Antarctica, formed by wet-based mountain glaciation and not by the present ice sheet: Boreas, v. 23, p. 139-148.

Holness, S.D., 2004, Sediment movement rates and processes on cinder cones in the maritime subantarctic (Marion Island): Earth Surface Processes and Landforms, v. 29, p. 91-103.

Hooper, D.M., 1999, Cinder movement experiments on scoria cone slopes: Rates and direction of transport: Landform Analysis, v. 2, p. 5-18.

152

Hooper, D.M., and Sheridan, M.F., 1998, Computer-simulation models of scoria cone degradation: Journal of Volcanology and Geothermal Research, v. 83, p. 241-167.

Howat, I.M., Negrete, A., and Smith, B.E., 2014, The Greenland Ice Mapping Project (GIMP) land classification and surface elevation data sets: The Cryosphere, v. 8, p. 1509-1518.

Inbar, M., Gilichinsky, M., Melekestsev, I., Melnikov, D., and Zaretskaya, N., 2011, Morphometric and morphological development of Holocene cinder cones: A field and remote sensing study in the Tolbachik volcanic field, Kamchatka: Journal of Volcanology and Geothermal Research, v. 201, p. 301-311.

Inbar, M., Hubp, J.L., and Ruiz, L.V., 1994, The geomorphological evolution of the Paricutin cone and lava flows, Mexico, 1943-1990: Geomorphology, v. 9, p. 57-76.

Jamieson, S.S.R., Sugden, D.E., and Hulton, N.R.J., 2010, The evolution of the subglacial landscape of Antarctica: Earth and Planetary Science Letters, v. 293, p. 1- 27.

Jiménez-Espinosa, R., Vázquez, M., and Jiménez-Millán, J., 2007, Differential weathering of granitic stocks and landscape effects in a Mediterranean climate, Southern Iberian Massif (Spain): Catena, v. 70, p. 243-252.

Johnsen, R.L., Smith, E.I., and Biek, R.F., 2010, Subalkaline volcanism in the Black Rock Desert and Markagunt Plateau Volcanic Fields of south-central Utah, in Carney, S.M., Tabet, D.E., and Johnson, C.L., eds., Geology of South-Centrla Utah: Utah Geological Association Publication 39, p. 109-150.

Karátson, D., Thouret, J.-C., Moriya, I., and Lomoschitz, A., 1999, Erosion calderas: origins, processes, structural and climatic control: Bulletin of Volcanology, v. 61, p. 174-193.

Kereszturi, K., Jordan, G., Németh, K., and Dóniz-Páez, J.F., 2012, Syn-eruptive morphometric variability of monogenetic scoria cones: Bulletin of Volcanology, v. 74, p. 2171-2185.

Kervyn, M., Ernst, G.G.J., Carracedo, J.-C., and Jacobs, P., 2012, Geomorphometric variability of “monogenetic” volcanic cones: Evidence from Mauna Kea, Lanzarote, and experimental cones: Geomorphology, v. 136, p. 59-75.

Kwon, J., Min, K., Bickel, P., and Renne, P., Statistical methods for jointly estimating the decay constant of 40K and the age of a dating standard: Mathematical Geology, v. 34, p. 457-474.

153

Kyle, P.R., 1976, Geology, mineralogy and geochemistry of the Late Cenozoic McMurdo Volcanic Group, Victoria Land, Antarctica [Ph.D. thesis]: Wellington, New Zealand, Victoria University of Wellington, 444 p.

Kyle, P.R., 1981a, Geological history of Hut Point Peninsula as inferred from DVDP 1, 2, and 3 drillholes and surface mapping, in McGinnis, L.D., ed., Dry Valley Drilling Project: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 33, p. 427-445.

Kyle, P.R., 1981b, Evolution of a basanite – phonolite sequence, Hut Point Peninsula, Antarctica – Evidence from Dry Valley Drilling project drillholes 1, 2, and 3: Journal of Petrology, v. 22, p. 451-500.

Kyle, P.R., 1981c, Glacial history of the McMurdo Sound area as indicated by the distribution and nature of McMurdo Volcanic Group rocks, in McGinnis, L.D., ed., Dry Valley Drilling Project: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 33, p. 403-412.

Kyle, P.R., 1987, Hut Point Peninsula, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 109-112.

Kyle, P.R., 1990a, Erebus Volcanic Province Summary, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 81-88.

Kyle, P.R., 1990b, McMurdo Volcanic Group, Western Ross Embayment: Introduction, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 19-25.

Kyle, P.R., Adams, J., and Rankin, P.C., 1979, Geology and petrology of the McMurdo Volcanic Group at Rainbow Ridge, Brown Peninsula, Antarctica: Geological Society of America Bulletin, v. 90, p. 676-688.

Kyle, P.R., Moore, J.A., and Thirlwall, M.F., 1992, Petrologic evolution of anorthoclase phonolite lavas at Mount Erebus, Ross Island, Antarctica: Journal of Petrology, v. 33, p. 849-875.

Kyle, P.R., and Muncy, H.L., 1989, Geology and geochronology of McMurdo Volcanic Group rocks in the vicinity of Lake Morning, McMurdo Sound, Antarctica: Antarctic Science, v. 1, p. 345-350.

154

Lawler, D.M., 1993, Needle ice processes and sediment mobilization on river banks: the River Ilston, West Glamorgan, UK: Journal of Hydrology, v. 150, p. 81-114.

Lawver, L.A., and Gahagan, L.M., 1994, Constraints on timing of extension in the Ross Sea region: Terra Antarctica, v. 1, p. 545-552.

Levy, R., Cody, R., Crampton, J., Fielding, C., Golledge, N., Harwood, D., Henrys, S., McKay, R., Naish, T., Ohneiser, C., Wilson, G., Wilson, T., and Winter, D., 2012, Late Neogene climate and glacial history of the Southern Victoria Land coast from integrated drill core, seismic, and outcrop data: Global and Planetary Change, v. 80- 81, p. 61-84.

Lewis, A.R., Marchant, D.R., Ashworth, A.C., Hemming, S.R., and Machlus, M.L., 2007, Major middle Miocene global climate change: Evidence from East Antarctica and the Transantarctic Mountains: Geological Society of America Bulletin, v. 119, p. 1449- 1461.

Lisiecki, L.E., and Raymo, M.E., 2005, A Pliocene-Pleistocene stack of 57 globally distributed benthic δO18 records: Paleoceanography, v. 20, p. 1-17.

Lloyd Davies, M.T., Atkins, C.B., van der Meer, J.J.M., Barrett, P.J., and Hicock, S.R., 2009, Evidence for cold-based glacial activity in the Alan Hills, Antarctica: Quaternary Science Reviews, v. 28, p. 3124-3137.

Mankinen, E.A., and Cox, A., 1988, Paleomagnetic investigation of some volcanic rocks from the McMurdo Volcanic Province, Antarcitca: Journal of Geophysical Research, v. 93, p. 11,599-11,612.

Marchant, D.R., Denton, G.H., Sugden, D.E., and Swisher III, C.C., 1993, Miocene glacial stratigraphy and landscape evolution of the western Asgard Range, Antarctica: Geografiska Annaler, v. 75, p. 303-330.

Martin, A.P., Cooper, A.F., and Dunlap, J., 2010, Geochronology of Mount Morning, Antarctica: two-phase evolution of a long-lived trachyte-basanite-phonolite eruptive center: Bulletin of Volcanology, v. 72, p. 357-371.

Martin, U., and Németh, K., 2006, How Strombolian is a “Strombolian” scoria cone? Some irregularities in scoria cone architecture from the Transmexican Volcanic Belt, near Volcán Ceboruco, (Mexico) and Al Haruj (Libya): Journal of Voclanology and Geothermal Research, v. 155, p. 104-118.

Mashimbye, Z.E., de Clercq, W.P., and Niekerk, A.V., 2014, An evaluation of digital elevation models (DEMs) for delineating land components: Geoderma, v. 213, p. 312-319. 155

Mattsson, H.B., and Tripoli, B.A., 2011, Depositional characteristics and volcanic landforms in the Lake Natron-Engaruka monogenetic field, northern Tanzania: Journal of Volcanology and Geothermal Research, v. 203, p. 23-34.

Maynard, J.J., and Johnson, M.G., 2014, Scale-dependency of LiDAR derived terrain attributes in quantitative soil-landscape modeling: Effects of grid resolution vs. neighborhood extent: Geoderma, v. 230-231, p. 29-40.

McIntosh, W.C., 2000, 40Ar/39Ar Geochronology of tephra and volcanic clasts in CRP- 2A, Victoria Land Basin, Antarctica: Terra Antarctica, v. 7, p. 621-630.

McKay, R.M., Dunbar, G.B., Naish, T.R., Barrett, P.J., Carter, L., and Harper, M., 2008, Retreat History of the West Antarctic Ice (Sheet) Shelf in Western Ross Sea since the Last Glacial Maximum from deep-basin sediment core: Paleogeography, Paleoclimatology, Paleoecology, v. 260, p. 168-183.

McKay, R., Browne, G., Carter, L., Cowan, E., Dunbar, G., Krissek, L., Naish, T., Powell, R., Reed, J., Talarico, F., and Wilch, T., 2009, The stratigraphic signature of the late Cenezoic Antarctic Ice Sheets in the Ross Embayment: GSA Bulletin, v. 121, p. 1537-1561.

McKay, R., Naish, T., Carter, L., Riesselman, C., Dunbar, R., Sjunneskog, C., Winter, D., Sangiorgi, F., Warren, C., Pagani, M., Schouten, S., Willmott, V., Levy, R., DeConto, R., and Powell, R.D., 2012, Antarctic and Southern Ocean influences on Late Pliocene global cooling: Proceedings of the National Academy of Sciences of the United States of America, v. 109, p. 6423-6428.

Millan, C., 2013, Syntectonic fluid flux in a glaciated rift basing: Record from vein arrays in the AND-1B and AND-2A sedimentary rock cores, Victoria Land Basin, Antarctica [Ph.D. thesis]: Columbus, The Ohio State University, 225 p.

Miller, K.G., Wright, J.D., and Fairbanks, R.G., 1991, Unlocking the ice house: Oligocene-Miocene oxygen isotopes, eustasy, and margin erosion: Journal of Geophysical Research, v. 96B, p. 6829-6842.

Moholdt, G., and Kääb, A., 2012, A new DEM of the Austfonna ice cap by combining differential SAR interferometry with ICESat laser altimetry: Polar Research, v. 31, 18460, 11 p.

Moore, J.A., and Kyle, P.R., 1986, Mantle upwelling and evolution of phonolitic magmas at Ross Island: International Volcanological Congress Abstracts, p. 188.

Mora, O.E., Lenzano, M.G., Toth, C.K., and Grejner-Brzezinska, D.A., 2014, Analyzing 156

the effects of spatial resolution for small landslide susceptibility and hazard mapping, in The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-1, ISPRS Technical Commission I Symposium, Denver, Colorado, p. 293-300.

Naish, T., Powell, R., Levy, R., Wilson, G., Scherer, R., Talarico, F., Krissek, L., Niessen, F., Pompilio, M., Wilson, T., Carter, L., DeConto, R., Huybers, P., McKay, R., Pollard, D., Ross, J., Winter, D., et al., 2009, Obliquity-paced Pliocene West Antarctic ice sheet oscillations: Nature, v. 458, p. 322-328.

Noh, M.-J., and Howat, I.M., 2015, Automated stereo-photogrammetric DEM generation at high latitudes: Surface Extraction with TIN-based Search-space Minimization (SETSM) validation and demonstration over glaciated regions: GIScience & Remote Sensing, v. 52, p. 198-217.

O’Connor, W.P., and Bromwich, D.H., 1988, Surface airflow around Windless Bight, Ross Island, Antarctica: Quarterly Journal of the Royal Meteorological Society, v. 114, p. 917-938.

Panter, K.S., Dunbar, N.W., Scanlan, M.K., Wilch, T.I., Fargo, A.J., and McIntosh, W.C., 2011, Petrogenesis of alkaline magmas at Minna Bluff Antarctica: evidence for multi- stage differentiation and complex mixing processes: American Geophysical Union Fall Meeting, San Francisco, California, Abstract V31F-2590.

Parrot, J., 2007a, Study of volcanic cinder cone evolution by means of high resolution DEMs, in Proceedings, MODSIM 2007 International Congress on Modelling and Simulation, Christchurch: Modelling and Simulation Society of Australia and New Zealand, p. 1356-1362.

Parrot, J., 2007b, Tri-dimensional parameterisation: an automated treatment to study the evolution of volcanic cones: Géomorphologie: relief, processus, environnement, v. 3, p. 247-258.

Passchier, S., Browne, G., Field, B., Fielding, C.R., Krissek, L.A., Panter, K., and Pekar, S.F., 2011, Early and middle Miocene Antarctic glacial history from the sedimentary facies distribution in the AND-2A drill hole, Ross Sea, Antarctica: GSA Bulletin, v. 123, p. 2352-2365.

Paulsen, T.S., and Wilson, T.J., 2009, Structure and age of volcanic fissures on Mount Morning: A new constraint on Neogene to contemporary stress in the West Antarctic rift, southern Victoria Land, Antarctica: Geological Society of America Bulletin, v. 121, p. 1071-1088.

157

Paulsen, T.S., and Wilson, T.J., 2010, New criteria for systematic mapping and reliability assessment of monogenetic volcanic vent alignments and elongate volcanic vents for crustal stress analyses: Tectonophysics, v. 482, p. 16-28.

Pelletier, J.D., and Cline, M.L., 2007, Nonlinear slope-dependent sediment transport in cinder cone evolution: Geology, v. 35, p. 1067-1070.

Pollard, D., and DeConto, R.M., 2009, Modeling West Antarctic ice sheet growth and collapse through the past five million years: Nature, v. 458, p. 329-332.

Porter, S.C., 1972, Distribution, morphology, and size frequency of cinder cones on Mauna Kea Volcano, Hawaii: Geological Society of America Bulletin, v. 83, p. 3607- 3612.

Powell, R.D., and Domack, E.W., 2002, Glacimarine environments, in Menzies, J., ed., Modern and Past Glacial Environments: Boston, Butterworth-Heinemann, p. 361-390.

Pye, K., 1986, Mineralogical and textural controls on the weather of granitoid rocks: Catena, v. 13, p. 47-57.

Rapprich, V., Cajz, V., Košťák, M., Pécskay, Z., Řídkošil, T., Raška, P., and Radoň, M., 2007, Reconstruction of eroded monogenic Strombolian cones of Miocene age: A case study on character of volcanic activity of the Jičín Volcanic Field (NE Bohemia) and subsequent erosional rates estimation: Journal of Geosciences, v. 52, p. 169-180.

Riedel, C., Ernst, G.G.J., and Riley, M., 2003, Controls on the growth and geometry of pyroclastic constructs: Journal of Volcanology and Geothermal Research, v. 127, p. 121-152.

Rilling, S.E., 2009, Geochronological and geochemical assessment of Cenozoic volcanism from the Terror Rift region of the West Antarctic Rift System [Ph.D. thesis]: Ann Arbor, University of Michigan, 143 p.

Risso, C., Németh, K., Combina, A.M., Nullo, F., and Drosina, M., 2008, The role of phreatomagmatism in a Plio-Pleistocene high-density scoria cone field: Llancanelo Volcanic Field (Mendoza), Argentina: Journal of Volcanology and Geothermal Research, v. 169, p. 61-86.

Rocchi, S., Armienti, P., D’Orazio, M., Tonarini, S., Wijbrans, J.R., and Di Vincenzo, G., 2002, Cenozoic magmatism in the western Ross Embayment: Role of mantle plume versus plate dynamics in the development of the West Antarctic Rift System: Journal of Geophysical Research, v. 107, Article 2195, 22 p.

158

Rocchi, S., Storti, F., Di Vincenzo, G., and Rossetti, F., 2003, Intraplate strike-slip tectonics as an alternative to mantle plume activity for the Cenozoic rift magmatism in the Ross Sea region, Antarctica, in Storti, F., Holdsworth, R.E., and Salvini, F., eds., Intraplate Strike-Slip Deformation Belts: Geological Society of London Special Publications, v. 210, p. 145-158.

Rooney, T.O., Bastow, I.D., and Keir, D., 2011, Insights into extensional processes during magma assisted rifting: evidence from aligned scoria cones: Journal of Volcanology and Geothermal Research: v. 201, p. 83-96.

Ross, J.I., McIntosh, W.C., and Wilch, T.I., 2012, Detailed Ar-Ar geochronology of volcanism at Minna Bluff, Antarctica: two-phased growth and influence on Ross Ice Shelf: American Geophysical Union Fall Meeting, San Francisco, California, Abstract C31A-0578.

Rowland, S., Jurado-Chichay, Z., Ernst, G.G.J., and Walker, G.P.L., 2009, Pyroclastic deposits and lava flows from the 1759-1774 erupsion of El Jorullo, Mexico: Aspects of ‘violent Strombolian’ activity and comparison with Paricutin, in Thordarson, T., Self, S., Larsen, G., Rowland, S., and Hoskuldsson, A., eds., Studies in Volcanology: The Legacy of Georges Walker: London, Geological Society, Special Publication of IAVCEI, p. 105-128.

Scally, F.A., and Owens, I.F., 2004, Morphometric controls and geomorphic responses on fans in the Southern Alps, New Zealand: Earth Surface Processes and Landforms, v. 29, p. 311-322.

Scambos, T.A., and Haran, T., 2002, An image-enhanced DEM of the Greenland ice sheet: Annals of Glaciology, v. 34, p. 291-298.

Schmidt-Thome, M., Mueller, P., and Tessensohn, F., 1986, Malta Plateau, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 53-59.

Settle, M., 1979 – The structure and emplacement of cinder cone fields: American Journal of Science, v. 279, p. 1089-1107.

Shipp, S., Anderson, J., and Domack, E., 1999, Late Pleistocene-Holocene retreat of the West Antarctic Ice Sheet system in the Ross Sea: Part 1—Geophysical results: Geological Society of America Bulletin, v. 111, p. 1486-1516.

Song, Y., Liu, L., Ping, Y., and Tong, Y., 2005, A review of soil erodibility in water and wind erosion research: Journal of Geogrpahical Sciences, v. 15, p. 167-176.

159

Stockton, P.H., and Gillette, D.A., 2006, Field measurement of the sheltering effect of vegetation on erodible land surfaces: Land Degradation and Development, v. 2, p. 77- 85.

Sucipta, I.G.B.E., Takashima, I., and Muraoka, H., 2006, Morphometric age and petrological characteristics of volcanic rocks from the Bajawa Cinder Cone Complex, Flores, Indonesia: Journal of Mineralogical and Petrological Sciences, v. 101, p. 48- 68.

Sugden, D.E., Balco, G., Cowdery, S.G., Stone, J.O., and Sass III, L.C., 2005, Selective glacial erosion and weather zones in the coastal mountains of Marie Byrd Land, Antarctica: Geomorphology, v. 67, p. 317-334.

Sugden, D.E., Denton, G.H., and Marchant, D.R., 1995, Landscape evolution of the Dry Valleys, Transantarctic Mountains: Tectonic implications: Journal of Geophysical Research, v. 100, p. 9949-9967.

Sugden, D.E., and Denton, G., 2004, Cenozoic landscape evolution of the Convoy Range to Mackay Glacier area, Transantarctic Mountains: onshore to offshore synthesis: Geological Society of America Bulletin, v. 116, p. 840-857.

Sugden, D.E., Summerfield, M.A., Denton, G.H., Wilch, T.I., McIntosh, W.C., Marchant, D.R., and Rutford, R.H., 1999, Landscape development in the Royal Society Range, southern Victoria Land, Antarctica: stability since the mid-Miocene: Geomorphology, v. 28, p. 181-200.

Sugden, D.E., and Watts, S.H., 1977, Tors, felsenmeer, and glaciation in northern Cumberland Peninsula, Baffin Island: Canadian Journal of Earth Sciences, v. 14, p. 2817-2823.

Talarico, F.M., McKay, R.M., Powell, R.D., Sandroni, S., and Naish, T., 2012, Late Cenezoic oscillations of Antarctic ice sheets revealed by provenance of basement clasts and grain detrital modes in ANDRILL core AND-1B: Global and Planetary Change, v. 96-97, p. 23-40.

Tauxe, L., Gans, P., and Mankinen, E.A., 2004, Paleomagnetism and 40Ar/39Ar ages from volcanics extruded during the Matuyama and Brunhes Chrons near McMurdo Sound, Antarctica: Geochemistry, Geophysics, Geosystems, v. 5, Article Q06H12, 20 p.

Tibaldi, A., 1995, Morphology of pyroclastic cones and tectonics: Journal of Geophysical Research, v. 100, pages 24521-24535.

160

Toutin, T., Blondel, E., Clavet, D., and Schmitt, C., 2013, Stereo radargrammetry with Radarsat-2 in the Canadian Arctic: IEEE Transactions on Geoscience and Remote Sensing, v. 51, p. 2601-2609.

Valentine, G.A., Krier, D.J., Perry, F.V., and Heiken, G., 2005, Scoria cone construction mechanisms, Lathrop Wells volcano, southern Nevada, USA: Geological Society of America Bulletin, v. 33, p. 629-632.

Valentine, G.A., Krier, D.J., Perry, F.V., and Heiken, G., 2007, Eruptive and geomorphic processes at the Lathrop Wells scoria cone volcano: Journal of Volcanology and Geothermal Research, v. 161, p. 57-80.

Valentine, G.A., Perry, F.V., Krier, D., Keating, G.N., Kelley, R.E., and Cogbill, A.H., 2006, Small-volume basaltic volcanoes: Eruptive products and processes, and posteruptive geomorphic evolution in Crater Flat (Pleistocene), southern Nevada: Geological Society of America Bulletin, v. 118, p. 1,313-1,330.

Van den Broeke, M.R., and van Lipzig, N.P.M., 2003, Factors controlling the near- surface wind field in Antarctica: Monthly Weather Review, v. 131, p. 733-743.

Waller, R.I., 2001, The influence of basal processes on the dynamic behavior of cold- based glaciers: Quaternary International, v. 86, p. 117-128.

Waller, R.I., and Hart, J.K., 1999, Mechanisms and patterns of motion associated with the basal zone of an arctic glacier: Russell Glacier, Greenland: Journal of Glacial Geology and Geomorphology, v. 21, p. 1-20.

Watson, T., Nyblade, A., Weins, D.A., Anandakrishnan, S., Benoit, M., Shore, P.J., Voigt, D., and VanDecar, J., 2006, P and S velocity structure of the upper mantle beneath the Transantarctic Mountains, East Antarctic craton, and Ross Sea from travel time tomography: Geochemistry, Geophysics, Geosystems, v. 7, Article Q07005, 17 p.

Webb, P.N., 1974, Micropaleontology, paleoecology and correlation of the Pecten Gravels, Wright Valley, Antarctica, and descriptions of Trochoelphidiella onyxi n. gen., n. sp.: Journal of Foraminiferal Research, v. 4, p. 185-199.

Webb, P.N., and Wrenn, J.H., 1982, Upper Cenozoic micropaleontology and biostratigraphy of eastern Taylor Valley, Antarctica, in Craddock, C., Antarctic Geoscience: Symposium on Antarctic Geology and Geophysics: Madison, University of Wisconsin Press, p. 1117-1122.

161

Wilch, T.I., Denton, G.H., Lux, D.R., and McIntosh, W.C., 1993, Limited Pliocene glacier extent and surface uplift in middle Taylor Valley, Antarctica: Geografiska Annaler, v. 75, p. 331-351.

Wilch, T.I., McIntosh, W.C., Panter, K.S., Dunbar, N.W., Smellie, J.L., Fargo, A.G., Scanlan, M.K., Zimmerer, M.J., Ross, J., and Bosket, M.E., 2008, Volcanic and glacial geology of the Miocene Minna Bluff Volcanic Complex, Antarctica: American Geophysical Union Fall Meeting, San Francisco, California, Abstract V11F-06.

Wilch, T.I., McIntosh, W.C., Panter, K.S., Dunbar, N.W., Smillie, J., Fargo, A.G., Ross, J.I., Antibus, J.V., and Scanlan, M.K., 2011, Two-state growth of the Late Miocene Minna Bluff Volcanic Complex, Ross Embayment, Antarctica: implications for ice- sheet and volcanic histories: American Geophysical Union Fall Meeting, San Francisco, California, Abstract V31F-2591.

Williams, P.J., and Smith, M.W., 1989, The Frozen Earth: Fundamentals of Geocryology: Cambridge, Cambridge University Press, 306 p.

Wilson, G.S., Levy, R.H., Naish, T.R., Powell, R.D., Florindo, F., Ohneiser, C., Sagnotti, L., Winter, D.M., Cody, R., Henrys, S., Ross, J., Krissek, L., Niessen, F., Pompillio, M., Scherer, R., et al., 2012, Neogene tectonic and climatic evolution of the Western Ross Sea, Antarctica – Chronology of events from the AND-1B drill hole: Global and Planetary Change, v. 96-97, p. 189-203.

Wilson, T.J., 1993, Jurassic faulting and magmatism in the Transantarctic Mountains: Implcations for Gondwana breakup, in Findlay, R.H., Bands, M.R., Unrug, R., and Veevers, J., eds., Gondwana 8 – Assembly, Evolution, and Dispersal: Rotterdam, Netherlands, A.A. Balkema, p. 563-572.

Winberry, J.P., and Anandakrishnan, S., 2004, Crustal structure of the West Antarctic rift system and Marie Byrd Land hotspot: Geology, v. 32, p. 977-980.

Winter, D., Sjunneskog, C., Schere, R., Maffioli, P., Riesselman, C., and Harwood, D., 2010, Pliocene-Pleistocene diatom biostratigraphy of nearshore Antarctica from the AND-1B drillcore, McMurdo Sound: Global and Planetary Change, v. 96-97, p. 59- 74.

Wood, C.A., 1980a, Morphometric evolution of cinder cones: Journal of Volcanology and Geothermal Research, v. 7, p. 387-413.

Wood, C.A., 1980b, Morphometric analysis of cinder cone degradation: Journal of Volcanology and Geothermal Research, v. 8, p. 137-160.

162

Wrenn, J., and Webb, P.N., 1982, Physiographic analysis and interpretation of the Ferrar Glacier – Victoria Valley area, Antarctica, in Craddock, C., ed., Third Symposium on Antarctic Geology and Geophysics: Madison, University of Wisconsin Press, p. 1091-1099.

Wright, A.C., 1980, Landforms of McMurdo Volcanic Group, Southern Foothills of Royal Society Range, Antarctica: New Zealand Journal of Geophysics, v. 23, p. 605- 613.

Wright, A.C., and Kyle, P.R., 1986, White Island, Black Island, and Brown Peninsula, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 113-116.

Wright, A.C., and Kyle, P.R., 1987a, Minna Bluff, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 117-119.

Wright, A.C., and Kyle, P.R., 1987b, Mount Discovery, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 120-123.

Wright, A.C., and Kyle, P.R., 1987c, Mount Morning, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 124-127.

Wright, A.C., and Kyle, P.R., 1987d, Mason Spur, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 128-130.

Wright, A.C., and Kyle, P.R., 1987e, Royal Society Range, in LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes of the Antarctic Plate and Southern Oceans: Washington, DC, American Geophysical Union, Antarctic Research Series, v. 48, p. 128-130.

Wright-Grassham, A.C., 1987, Volcanic geology, mineralogy, and petrogenesis of the Discovery Volcanic Subprovince, Southern Victoria Land, Antarctica [Ph.D. Thesis]: Socorro, New Mexico Institute of Mining and Technology, 460 p.

163

Appendix A: Compiled EVP Age Data and Date Source Map

Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Mount Morning Hurricane Ridge 164.21000 -78.40200 -0.290 0.36 40Ar/39Ar Flow 3 Paulsen and Wilson (2009) Mount Morning Hurricane Ridge 164.16000 -78.45200 -0.270 0.22 40Ar/39Ar Cone Paulsen and Wilson (2009)

Mount Morning Riviera Ridge 163.54000 -78.42500 -0.020 0.02 40Ar/39Ar Flow 3 Paulsen and Wilson (2009) Mount Erebus Northwest of main crater 167.07614 -77.51781 0.001 0.01 40Ar/39Ar Flow 3 Harpel et al. (2004) Mount Erebus Upper Ice Tower Ridge 167.11881 -77.53267 0.004 0.00 40Ar/39Ar Cone Harpel et al. (2004)

Mount Erebus 40 39

164 South of main crater 167.16028 -77.53375 0.006 0.00 Ar/ Ar Flow 2 Harpel et al. (2004) Mount Erebus Tramways 167.13114 -77.52136 0.009 0.00 40Ar/39Ar Flow 2 Harpel et al. (2004)

Mount Erebus Lower Ice Tower Ridge 167.08647 -77.53386 0.009 0.01 40Ar/39Ar Flow 2 Harpel et al. (2004) Mount Erebus Nausea Knob 167.14558 -77.51964 0.010 0.01 40Ar/39Ar Flow 1 Harpel et al. (2004) Mount Erebus Lower Hut 167.15756 -77.50769 0.010 0.01 40Ar/39Ar Flow 2 Harpel et al. (2004) Mount Erebus Lower Hut 167.09035 -77.50842 0.011 0.08 40Ar/39Ar Flow 2 Harpel et al. (2004) Mount Erebus Lower Hut 167.15756 -77.50769 0.011 0.01 40Ar/39Ar Flow 2 Harpel et al. (2004) Mount Erebus Southeast of main crater 167.17856 -77.53783 0.012 0.00 40Ar/39Ar Flow 2 Harpel et al. (2004) Mount Erebus Southwest of main crater 167.12903 -77.53497 0.017 0.01 40Ar/39Ar Flow 3 Harpel et al. (2004) Mount Erebus Southwest of main crater 167.09406 -77.53728 0.021 0.00 40Ar/39Ar Flow 2 Harpel et al. (2004) Mount Erebus Three Sisters 166.96667 -77.56667 0.026 0.00 40Ar/39Ar Flow 1 Esser et al. (2004) Mount Erebus Hooper's Shoulder 166.88333 -77.53333 0.033 0.01 40Ar/39Ar Cone Esser et al. (2004)

Mount Erebus William's Cliff 166.80133 -77.58017 0.057 0.01 40Ar/39Ar Cone Esser et al. (2004)

164

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Mount Morning Hurricane Ridge 163.95000 -78.47500 0.060 0.08 40Ar/39Ar Cone Paulsen and Wilson (2009)

Mount Discovery 164.73000 -78.29000 0.060 0.01 40Ar/39Ar Flow 3 Tauxe et al. (2004) Mount Morning Mason Spur 164.36000 -78.55600 0.070 0.08 40Ar/39Ar Flow 3 Paulsen and Wilson (2009) Mason Spur 164.35878 -78.55147 0.070 0.08 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Mount Morning Hurricane Ridge 164.21000 -78.39000 0.080 0.01 40Ar/39Ar Flow 2 Tauxe et al. (2004) Royal Society Range 163.46726 -78.29363 0.080 0.13 K-Ar Flow 3 Armstrong (1978) Mount Morning Hurricane Ridge 164.23000 -78.39000 0.120 0.02 40Ar/39Ar Flow 1 Tauxe et al. (2004) Mount Morning Hurricane Ridge 164.27000 -78.39000 0.120 0.02 40Ar/39Ar Flow 2 Tauxe et al. (2004) Mount Erebus Hooper's Shoulder 166.80075 -77.51705 0.121 0.01 40Ar/39Ar Flow 3 Esser et al. (2004) Mount Morning Hurricane Ridge 164.20900 -78.40600 0.150 0.01 K-Ar Cone Martin et al. (2010)

Mount Erebus 167.09035 -77.50842 0.150 0.05 K-Ar Flow 3 Armstrong (1978) 165 Mount Erebus Bomb Peak 167.43333 -77.50833 0.157 0.01 40Ar/39Ar Flow 2 Esser et al. (2004)

Mount Morning Hurricane Ridge 164.22000 -78.37200 0.170 0.10 40Ar/39Ar Flow 1 Paulsen and Wilson (2009) Mount Discovery 164.80000 -78.31000 0.180 0.08 40Ar/39Ar Flow 2 Tauxe et al. (2004) Royal Society Range Pipecleaner 162.86480 -78.25577 0.196 0.09 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 163.46176 -78.28800 0.220 0.12 K-Ar Flow 3 Armstrong (1978) Mount Morning Mason Spur 164.39000 -78.53600 0.230 0.22 40Ar/39Ar Flow 3 Paulsen and Wilson (2009) Mason Spur 164.37834 -78.53619 0.230 0.22 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Royal Society Range Walcott Glacier-Roaring Valley 163.13728 -78.24404 0.242 0.05 40Ar/39Ar Flow 3 Sugden et al. (1999) Royal Society Range Walcott Glacier-Roaring Valley 163.17228 -78.24484 0.247 0.03 40Ar/39Ar Flow 2 Sugden et al. (1999) Royal Society Range Radian-Pipecleaner Glacier 162.89688 -78.23454 0.271 0.05 40Ar/39Ar Cone Sugden et al. (1999)

Mount Morning Hurricane Ridge 164.12000 -78.39000 0.280 0.02 40Ar/39Ar Cone Tauxe et al. (2004)

Royal Society Range Radian Glacier 162.74329 -78.20398 0.280 0.13 40Ar/39Ar Flow 1 Sugden et al. (1999) Mount Morning Hurricane Ridge 164.23000 -78.48200 0.290 0.02 K-Ar Cone Martin et al. (2010)

165

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Mount Morning Hurricane Ridge 164.22000 -78.37400 0.310 0.08 40Ar/39Ar Cone Paulsen and Wilson (2009)

Royal Society Range Radian Glacier 162.74165 -78.20614 0.320 0.04 40Ar/39Ar Flow 1 Sugden et al. (1999) Hut Point Peninsula 166.69000 -77.85000 0.330 0.02 40Ar/39Ar Flow 1 Tauxe et al. (2004) Hut Point Peninsula 166.70000 -77.84000 0.340 0.01 40Ar/39Ar Flow 2 Tauxe et al. (2004) Mount Erebus Abbott Peak 166.89528 -77.47720 0.342 0.02 40Ar/39Ar Cone Esser et al. (2004)

Hut Point Peninsula 166.76000 -77.84000 0.350 0.01 40Ar/39Ar Flow 2 Tauxe et al. (2004) Mount Morning Hurricane Ridge 164.27000 -78.37300 0.410 0.39 40Ar/39Ar Flow 3 Paulsen and Wilson (2009) Mount Morning Hurricane Ridge 164.22300 -78.43600 0.410 0.20 K-Ar Cone Martin et al. (2010)

Mount Erebus Abbott Peak 166.82500 -77.47167 0.430 0.04 40Ar/39Ar Flow 3 Esser et al. (2004) Hut Point Peninsula 166.65952 -77.84232 0.430 0.07 K-Ar Flow 3 Armstrong (1978) Mount Erebus 167.16560 -77.52940 0.440 0.09 K-Ar Cone Armstrong (1978)

166 Mount Erebus Abbott Peak 166.81402 -77.45245 0.508 0.02 40Ar/39Ar Cone Esser et al. (2004)

Mount Erebus Crash Nunatak 167.64330 -77.44463 0.520 0.12 40Ar/39Ar Flow 3 Esser et al. (2004) Mount Erebus Abbott Peak 166.90000 -77.46667 0.531 0.38 40Ar/39Ar Flow 3 Esser et al. (2004) Mount Erebus 167.16311 -77.52905 0.550 0.15 K-Ar Cone Armstrong (1978)

Hut Point Peninsula 166.65022 -77.84234 0.570 0.03 K-Ar Flow 3 Armstrong (1978) Royal Society Range Roaring Valley 163.08049 -78.25965 0.616 0.07 40Ar/39Ar Flow 2 Sugden et al. (1999) Hut Point Peninsula 166.83000 -77.80000 0.650 0.05 40Ar/39Ar Flow 3 Tauxe et al. (2004) Mount Morning Riviera Ridge 163.80600 -78.37600 0.660 0.03 K-Ar Cone Martin et al. (2010)

Royal Society Range 163.48793 -78.30017 0.710 0.16 K-Ar Flow 2 Armstrong (1978) Daily Islands 165.02000 -77.88000 0.770 0.03 40Ar/39Ar Flow 1 Tauxe et al. (2004) Brown Peninsula Juergens Island 165.03300 -77.88500 0.775 0.02 40Ar/39Ar Cone Del Carlo et al., 2009

Mount Terror Cape Crozier 169.28429 -77.46242 0.800 0.14 K-Ar Flow 3 Armstrong (1978) Mount Erebus Mount Terra Nova 167.95165 -77.51660 0.800 0.50 K-Ar Cone Armstrong (1978)

166

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Mount Erebus 167.14742 -77.48204 0.810 0.02 K-Ar Flow 2 Armstrong (1978) Royal Society Range 163.18389 -78.25194 0.840 0.07 K-Ar Flow 1 Armstrong (1978) Royal Society Range Roaring Valley 162.90067 -78.30313 0.853 0.05 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 162.90000 -78.30200 0.860 0.23 40Ar/39Ar Cone Lawrence et al. (2009)

Royal Society Range 163.08000 -78.26000 0.880 0.08 40Ar/39Ar Flow 2 Lawrence et al. (2009) Royal Society Range Roaring Valley 163.14368 -78.25236 0.900 0.13 40Ar/39Ar Flow 2 Sugden et al. (1999) Royal Society Range 163.18471 -78.25159 0.900 0.09 K-Ar Flow 1 Armstrong (1978) Royal Society Range Roaring Valley 163.23875 -78.26421 0.981 0.07 40Ar/39Ar Flow 1 Sugden et al. (1999) Hut Point Peninsula 166.73895 -77.81066 1.000 0.15 K-Ar Flow 2 Armstrong (1978) Hut Point Peninsula 166.71400 -77.85400 1.030 0.10 40Ar/39Ar Flow 3 Lawrence et al. (2009) Mount Morning Hurricane Ridge 164.16700 -78.38300 1.060 0.02 K-Ar Flow 2 Martin et al. (2010)

167 Royal Society Range Roaring Valley 162.92521 -78.30384 1.065 0.00 40Ar/39Ar Flow 1 Sugden et al. (1999)

Royal Society Range Radian Glacier 162.96218 -78.23836 1.080 0.22 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 163.11652 -78.26330 1.120 0.14 K-Ar Flow 3 Armstrong (1978) Royal Society Range Howchin Glacier 163.59373 -78.18867 1.134 0.66 40Ar/39Ar Flow 1 Sugden et al. (1999) Royal Society Range Radian Glacier 162.72479 -78.22778 1.140 0.11 40Ar/39Ar Cone Sugden et al. (1999)

Mount Morning 163.53579 -78.48334 1.150 0.02 K-Ar Cone Armstrong (1978)

Royal Society Range Mt. Kemp 162.70571 -78.30622 1.170 0.45 40Ar/39Ar Cone Sugden et al. (1999)

Hut Point Peninsula 166.64000 -77.85000 1.180 0.01 40Ar/39Ar Flow 3 Tauxe et al. (2004) Mount Morning Riviera Ridge 163.54900 -78.45800 1.190 0.03 40Ar/39Ar Cone Martin et al. (2010)

Royal Society Range Roaring Valley 163.25413 -78.26379 1.210 0.18 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 163.28314 -78.33075 1.210 0.09 K-Ar Cone Armstrong (1978)

Mount Morning Riviera Ridge 163.80700 -78.45200 1.230 0.03 K-Ar Flow 1 Martin et al. (2010) Hut Point Peninsula 166.68000 -77.85100 1.230 0.02 40Ar/39Ar Flow 1 Lawrence et al. (2009)

167

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Royal Society Range Bulwark 163.55138 -78.28153 1.261 0.04 40Ar/39Ar Cone Sugden et al. (1999)

Mount Terror Cape Crozier 169.32326 -77.51231 1.290 0.05 K-Ar Cone Armstrong (1978)

Mount Terror Cape Crozier 169.20691 -77.46696 1.310 0.04 K-Ar Cone Armstrong (1978)

Mount Terror 168.93633 -77.50378 1.323 0.05 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Hut Point Peninsula 166.67000 -77.84900 1.330 0.12 40Ar/39Ar Flow 2 Lawrence et al. (2009) Mount Terror Cape Crozier 169.23000 -77.47000 1.330 0.02 40Ar/39Ar Flow 3 Tauxe et al. (2004) Mount Terror Cape Crozier 169.33000 -77.51400 1.360 0.01 40Ar/39Ar Cone Lawrence et al. (2009)

Royal Society Range Radian Glacier 162.96848 -78.21989 1.370 0.42 40Ar/39Ar Cone Sugden et al. (1999)

Mount Terror Cape Crozier 169.29200 -77.48700 1.380 0.05 40Ar/39Ar Cone Lawrence et al. (2009)

Mount Terror Cape Crozier 168.89572 -77.50555 1.432 0.02 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Mount Terror Cape Crozier 169.33200 -77.51300 1.450 0.06 40Ar/39Ar Cone Lawrence et al. (2009)

168 Taylor Valley East side of Rhone Glacier 162.25270 -77.70164 1.500 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Taylor Valley 162.13430 -77.75196 1.530 0.06 K-Ar Flow 3 Armstrong (1978) Royal Society Range Radian Glacier 163.00122 -78.21948 1.550 0.30 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range Radian Glacier 162.78155 -78.22837 1.600 0.25 40Ar/39Ar Flow 1 Sugden et al. (1999) Royal Society Range Radian Glacier 162.78694 -78.22570 1.620 0.28 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range Walcott Glacier 162.96173 -78.19783 1.630 0.34 40Ar/39Ar Flow 1 Sugden et al. (1999) Royal Society Range 163.57308 -78.30304 1.650 0.30 K-Ar Cone Armstrong (1978)

Royal Society Range 163.55793 -78.28040 1.660 0.40 K-Ar Cone Armstrong (1978)

Royal Society Range 163.31781 -78.32504 1.680 0.08 K-Ar Cone Armstrong (1978)

Royal Society Range Radian Glacier 162.89594 -78.21562 1.769 0.06 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 163.10665 -78.27168 1.780 0.19 K-Ar Flow 2 Armstrong (1978) Taylor Valley 162.25290 -77.70022 1.790 0.13 K-Ar Flow 1 Armstrong (1978) Ferrar Valley 162.73848 -77.76609 1.830 0.18 40Ar/39Ar Cone Sugden et al. (1999)

168

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Royal Society Range 163.50708 -78.30494 1.830 0.09 K-Ar Flow 2 Armstrong (1978) Taylor Valley 162.11797 -77.76618 1.840 0.11 K-Ar Flow 2 Armstrong (1978) Mount Morning Riviera Ridge 163.53300 -78.50200 1.850 0.03 K-Ar Cone Martin et al. (2010)

Royal Society Range Roaring Valley 163.16008 -78.26839 1.877 0.08 40Ar/39Ar Cone Sugden et al. (1999)

Mount Morning Riviera Ridge 163.64700 -78.48100 1.880 0.03 40Ar/39Ar Cone Martin et al. (2010)

Taylor Valley Northeast Sollas Glacier 162.59443 -77.70292 1.890 0.00 40Ar/39Ar Flow 3 Sugden et al. (1999) Ferrar Valley 162.43368 -77.85500 1.890 0.22 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range Roaring Valley 163.17302 -78.25608 1.890 0.30 40Ar/39Ar Flow 2 Sugden et al. (1999) Brown Peninsula 165.35228 -78.12009 1.910 0.19 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Royal Society Range Walcott Glacier 163.18630 -78.18560 1.910 0.14 40Ar/39Ar Flow 1 Sugden et al. (1999) Royal Society Range Roaring Valley 163.16783 -78.26859 1.925 0.09 40Ar/39Ar Cone Sugden et al. (1999)

169 Royal Society Range 163.72900 -78.25400 1.930 0.05 40Ar/39Ar Flow 2 Lawrence et al. (2009)

Royal Society Range Heald Island 163.73648 -78.25254 1.942 0.07 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 162.78700 -78.22400 1.990 0.04 40Ar/39Ar Flow 2 Lawrence et al. (2009) Royal Society Range Dromedary Platform 163.33058 -78.28291 1.990 0.60 40Ar/39Ar Flow 1 Sugden et al. (1999) Taylor Valley 162.13287 -77.76683 2.000 0.06 K-Ar Flow 3 Armstrong (1978) Royal Society Range 162.87900 -78.24400 2.080 0.65 40Ar/39Ar Cone Lawrence et al. (2009)

Royal Society Range Radian-Pipecleaner Glacier 162.88925 -78.24582 2.080 0.16 40Ar/39Ar Cone Sugden et al. (1999)

Ferrar Valley 162.60865 -77.80274 2.100 0.16 40Ar/39Ar Cone Sugden et al. (1999)

Brown Peninsula 165.26695 -78.11750 2.100 0.40 K-Ar Flow 1 Armstrong (1978) Royal Society Range 163.10632 -78.27105 2.100 0.09 K-Ar Flow 2 Armstrong (1978) White Island 167.49372 -78.09019 2.110 0.05 40Ar/39Ar Flow 2 Cooper et al. (2007) Royal Society Range Roaring Valley 163.15673 -78.27064 2.170 0.07 40Ar/39Ar Cone Sugden et al. (1999)

Taylor Valley Northeast Sollas Glacier 162.57715 -77.70651 2.190 0.00 40Ar/39Ar Flow 3 Sugden et al. (1999)

169

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Brown Peninsula 165.41308 -78.13519 2.200 0.09 K-Ar Flow 2 Armstrong (1978) Ferrar Valley 162.58500 -77.79424 2.220 0.11 40Ar/39Ar Cone Sugden et al. (1999)

Brown Peninsula 165.46388 -78.11762 2.250 0.05 K-Ar Flow 2 Armstrong (1978) Ferrar Valley 162.71708 -77.77598 2.380 0.09 40Ar/39Ar Cone Sugden et al. (1999)

Ferrar Valley 162.91344 -77.83983 2.390 0.33 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 163.30703 -78.27276 2.440 0.16 K-Ar Flow 2 Armstrong (1978) Taylor Valley West Sollas Glacier 162.58101 -77.73413 2.510 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Ferrar Valley 162.93705 -77.81768 2.520 0.11 40Ar/39Ar Cone Sugden et al. (1999)

Taylor Valley East of Bornes Glacier 162.12895 -77.76133 2.530 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range Radian Glacier 162.97011 -78.24022 2.534 0.05 40Ar/39Ar Cone Sugden et al. (1999)

Taylor Valley Marr Site 162.70859 -77.70797 2.550 0.00 40Ar/39Ar Cone Sugden et al. (1999)

170 Taylor Valley East side of LaCroix Glacier 162.58092 -77.67721 2.570 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Taylor Valley 162.55371 -77.70188 2.660 0.06 K-Ar Flow 3 Armstrong (1978) Ferrar Valley 162.60688 -77.80043 2.670 0.15 40Ar/39Ar Cone Sugden et al. (1999)

Brown Peninsula 165.38197 -78.08443 2.700 0.09 K-Ar Flow 2 Armstrong (1978) Taylor Valley East side of Rhone Glacier 162.25006 -77.70229 2.710 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Ferrar Valley 162.61684 -77.78905 2.720 0.12 40Ar/39Ar Cone Sugden et al. (1999)

Ferrar Valley 162.66296 -77.85010 2.770 0.08 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range 163.52187 -78.32590 2.880 0.15 K-Ar Flow 3 Armstrong (1978) Black Island 166.62570 -78.23540 2.900 1.40 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Taylor Valley 162.70203 -77.69983 2.930 0.10 K-Ar Flow 2 Armstrong (1978) Taylor Valley 162.56746 -77.73415 2.950 0.07 K-Ar Flow 2 Armstrong (1978) Taylor Valley West side of Matterhorn Glacier 162.34913 -77.68933 2.970 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Mount Bird 166.37269 -77.26769 3.000 0.15 K-Ar Flow 2 Armstrong (1978)

170

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Taylor Valley 162.56896 -77.70103 3.000 0.10 K-Ar Flow 3 Armstrong (1978) Mount Morning Riviera Ridge 163.57600 -78.47000 3.070 0.08 40Ar/39Ar Cone Martin et al. (2010)

Taylor Valley 162.55047 -77.73376 3.110 0.09 K-Ar Flow 2 Armstrong (1978) Mount Bird 166.38379 -77.27170 3.150 0.09 K-Ar Flow 1 Armstrong (1978) White Island 167.41122 -78.04178 3.290 0.10 40Ar/39Ar Flow 3 Cooper et al. (2007) Black Island 166.45194 -78.21859 3.350 0.14 K-Ar Flow 2 Armstrong (1978) Wright Valley 162.36012 -77.56480 3.400 0.30 40Ar/39Ar Cone Sugden et al. (1999)

Taylor Valley West side of Matterhorn Glacier 162.35034 -77.68957 3.470 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Mount Morning Hurricane Ridge 164.11000 -78.37000 3.500 0.20 40Ar/39Ar Flow 3 Paulsen and Wilson (2009) Wright Valley 162.39354 -77.48297 3.500 0.20 K-Ar Flow 3 Armstrong (1978) Taylor Valley East Sollas Glacier 162.63536 -77.71586 3.570 0.00 40Ar/39Ar Cone Sugden et al. (1999)

171 Mount Bird 166.40045 -77.24038 3.700 0.20 K-Ar Flow 2 Armstrong (1978)

Taylor Valley East side of Matterhorn Glacier 162.44056 -77.68310 3.740 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Wright Valley 162.14575 -77.51778 3.750 0.20 K-Ar Flow 3 Armstrong (1978) Black Island 166.43239 -78.21893 3.800 0.09 K-Ar Flow 3 Armstrong (1978) Mount Morning Gandalf Ridge 164.13200 -78.34300 3.880 0.05 K-Ar Flow 3 Martin et al. (2010) Taylor Valley East Sollas Glacier 162.62451 -77.72207 3.890 0.00 40Ar/39Ar Cone Sugden et al. (1999)

Black Island 166.34608 -78.21517 4.010 0.02 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Mount Discovery 165.41266 -78.33055 4.100 0.11 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Royal Society Range Heald Island 163.73150 -78.25415 4.260 0.18 40Ar/39Ar Cone Sugden et al. (1999)

Mount Morning Hurricane Ridge 164.27000 -78.40000 4.470 0.04 40Ar/39Ar Flow 1 Tauxe et al. (2004) Mount Bird 166.72626 -77.27218 4.500 0.60 K-Ar Cone Armstrong (1978)

White Island 167.45225 -78.07415 4.603 0.18 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

White Island 167.52683 -78.05178 4.680 0.06 40Ar/39Ar Flow 3 Cooper et al. (2007)

171

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Minna Bluff 165.67058 -78.45870 4.880 0.68 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

Mount Morning Riviera Ridge 163.63300 -78.45700 5.010 0.04 40Ar/39Ar Flow 2 Martin et al. (2010) White Island 167.21697 -78.14731 5.040 0.31 40Ar/39Ar Cone Cooper et al. (2007)

Mount Discovery 165.00450 -78.36783 5.300 0.14 K-Ar Cone Armstrong (1978)

Mason Spur 164.45000 -78.54500 6.130 0.20 K-Ar Cone Wright-Grassham (1987)

Royal Society Range Roaring Valley 163.10323 -78.27499 6.340 0.10 40Ar/39Ar Cone Sugden et al. (1999)

Royal Society Range Roaring Valley 163.22289 -78.24413 6.400 0.33 40Ar/39Ar Flow 2 Sugden et al. (1999) Royal Society Range Radian Glacier 162.73622 -78.22468 6.730 0.17 40Ar/39Ar Cone Sugden et al. (1999)

Black Island 166.57900 -78.21000 7.250 0.07 40Ar/39Ar Flow 2 Lawrence et al. (2009) White Island Camp Crater 167.45205 -78.16358 7.650 0.69 Pb-U Cone Cooper et al. (2007)

Minna Bluff 166.88428 -78.55467 8.319 0.35 40Ar/39Ar Cone Paulsen and Wilson (unpublished)

1 Minna Bluff 40 39 72 167.04093 -78.56820 8.320 0.25 Ar/ Ar Cone Paulsen and Wilson (unpublished)

Black Island 166.60700 -78.21900 9.020 0.05 40Ar/39Ar Flow 3 Lawrence et al. (2009) Royal Society Range Howchin Glacier 163.57850 -78.18775 10.500 1.10 40Ar/39Ar Flow 1 Sugden et al. (1999) Black Island 166.37419 -78.14696 10.900 0.40 K-Ar Flow 3 Armstrong (1978) Mason Spur 164.41700 -78.54500 11.400 0.20 K-Ar Cone Wright-Grassham (1987)

Black Island 166.23506 -78.12566 11.440 0.16 40Ar/39Ar Flow 1 Paulsen and Wilson (unpublished) Mason Spur 164.36700 -78.55300 11.500 0.10 K-Ar Cone Wright-Grassham (1987)

Mason Spur 164.46700 -78.54700 11.700 0.40 K-Ar Flow 3 Wright-Grassham (1987) Royal Society Range Walcott Glacier 163.30623 -78.21045 12.100 1.20 40Ar/39Ar Flow 1 Sugden et al. (1999) Royal Society Range Howchin Glacier 163.54280 -78.18463 12.430 0.22 40Ar/39Ar Flow 1 Sugden et al. (1999) Royal Society Range 163.56700 -78.18600 12.610 0.11 40Ar/39Ar Flow 2 Lawrence et al. (2009) Royal Society Range 163.58000 -78.18700 12.700 0.09 40Ar/39Ar Flow 1 Lawrence et al. (2009) Mount Morning Pinnacle Valley 163.78300 -78.37500 13.000 0.30 K-Ar Cone Wright-Grassham (1987)

172

(continued) Region Locality Longitude Latitude Age (Ma) Error Type Context Certainty Source Mount Morning Pinnacle Valley 163.74400 -78.37400 13.100 0.30 K-Ar Flow 3 Wright-Grassham (1987) Royal Society Range 163.52373 -78.33689 13.200 0.40 K-Ar Flow 3 Armstrong (1978) Royal Society Range 163.30800 -78.21000 13.420 0.18 40Ar/39Ar Flow 1 Lawrence et al. (2009) Royal Society Range 163.55511 -78.18603 13.800 0.20 K-Ar Flow 2 Armstrong (1978) Mount Morning Pinnacle Valley 163.76700 -78.36300 14.100 0.30 K-Ar Cone Wright-Grassham (1987)

Mount Morning Pinnacle Valley 163.80400 -78.37300 14.600 0.20 K-Ar Flow 1 Kyle and Muncy (1989) Mount Morning Pinnacle Valley 163.80200 -78.37200 15.200 0.20 K-Ar Cone Kyle and Muncy (1989)

Mount Morning Pinnacle Valley 163.80600 -78.37500 15.400 0.10 40Ar/39Ar Cone Martin et al. (2010)

Mount Morning Gandalf Ridge 164.13700 -78.34700 16.800 0.20 K-Ar Flow 1 Kyle and Muncy (1989) Mount Morning Gandalf Ridge 164.13500 -78.33900 17.200 0.20 K-Ar Flow 1 Kyle and Muncy (1989) Mount Morning Gandalf Ridge 164.12800 -78.35300 17.600 0.06 K-Ar Flow 2 Kyle and Muncy (1989) 173 Mount Morning Gandalf Ridge 164.14300 -78.33700 18.730 0.32 K-Ar Flow 2 Kyle and Muncy (1989)

Criteria for certainty of flow genesis: 1 Most certain - clear flow path 2 Certain - distinct to indistinct flow path or breaching direction and logical geographic proximity (e.g. downslope, isolated, etc.) 3 Least certain - indistinct to no flow path or breaching direction and logical geographic proximity

173

174

Figure 65. Map of the EVP showing the locations of compiled dates and whether they were derived from flow samples (circles) or cones (triangles) 174

Appendix B: MORVOLC and NETVOLC Parameters

MORVOLC Program Parameters (input_param.txt)

[paths] path_img = [MORVOLC_home]\Images\ fileDEM = [MORVOLC_home]\Images\[DEM].dat dirROI = [MORVOLC_home]\Contours dirResults = [MORVOLC_home]\Results\

[curves] equidist=2 ;equidistance of elevation curves, in meters equidist_type=FLOAT ;INT/FLOAT equidistance value type (integer or floating point) summit_factor=8 ;factor to determine at which elevation the summit region starts min_area_peak=1 ;minimum area, in pixel units, that a secondary curve has to have to be considered the base of a secondary peak dif_centroid=2 ;minimum difference between secondary curve centroids, in pixel units, for consideration as different secondary peaks/holes manual_summit=NO ;NO/YES defines if a user-defined summit region elevation is used (if YES, indicate elevation in summit_value) summit_value=0 ;user-defined summit region elevation (when manual_summit=YES)

[volume] vol_IDW=YES ;NO/YES defines if volume and height from IDW base are computed vol_TIN=YES ;NO/YES defines if volume and height from TIN base are computed vol_POLY1=YES ;NO/YES defines if volume and height from first degree polynomial base are computed vol_MAX=YES ;NO/YES defines if maximum volume from horizontal base is computed

[crater] crater?=NO ;NO/YES defines if a crater outline is used or not

[ENVI] KERNEL=3 ;kernel to be used for computing DEM-derived slope and shaded relief images SHADED_RELIEF_AZIMUTH=45 ;azimuthal angle to be used for computing shaded relief and 3D images SHADED_RELIEF_ELEVATION=45 ;elevation angle to be used for computing shaded relief and 3D images

175

NETVOLC Program Sample Parameters (input_param.txt) From WV01_20110224 (Cape Crozier)

[BATCH] dem=DEM_2_clip1.dat ;DEM file name volcanoesList=volcanoes.txt ;Volcanoes file name

[ENVIRONMENT] appMCF=f:\cygwin\bin\mcflight ;MCF solver appGREP=f:\cygwin\bin\grep ;grep command

[NETVOLC] net_plot_triang=y ;flag indicating if network triangulation plot is desired (y/n). Default is y. polar_plot_triang=y ;flag indicating if polar coordinate network triangulation plot is desired (y/n). Default is y. perc_threshold=100 ;percentage of arcs to be considered based on its cost. Default is 100 . perc_threshold_arcs=100 ;percentage of arcs to be considered based on its length. Default is 99. bin_size=1 ;bin size for estimating histogram (see idl histogram documentation). Default is 1. ang_threshold =5 ;border to be considered in the polar coordinate system for linking fictitious nodes to the network (in degrees). It means that nodes with an azimuth polar coordinate value within (−180; -180+ang_threshold) degrees will be linked to the supply node. Nodes with an azimuth polar coordinate value within (180-ang_threshold; 180) degrees will be linked to the demand node. Default is 5. smooth_width=2 ;smoothing factor of the final solution: default is 2. min_threshold_separation=0 ;minimum radial distance (in pixel units) from the central point of the solution. Default is 0. max_threshold_separation=650 ;maximum radial distance (in pixel units) from the central point of the solution. Default is equal or greater to window size extracted from the DEM. use_dem=n ;flag indicating if height information must be considered (y/n). Default is n. min_dem_height_filter=0 ;minimum height of the solution (if use_dem flag is set to y). max_dem_height_filter=985 ;maximum height of the solution (if use_dem flag is set to y). use_slope=n ;flag indicating if slope information must be considered (y/n). Default is n. slope_factor=1. ;factor establishing the influence of slope on the solution (when slope_factor flag is set to y). Default is 1. iterations=10 ;number of iterations to be performed. Default is 10. overflow=1.e+07 ;number considered an overflow. It is used for filtering arcs with an associated cost greater than this value. Default is 1.e+07. stdev_factor=1 ;number of standard deviations to be considered when statistics are calculated. Default is 1.

176 cancel_strategy=a ;It is used for reducing the network in every iteration. a: indicates network must be reduced cancelling arcs. n: indicates network must be reduced cancelling nodes. Default is a.

[ENVI] KERNEL=3 ;kernel to be used for estimating DEM derived products SHADED_RELIEF_AZIMUTH=45 ;azimuthal angle to be used for calculating shaded relief product SHADED_RELIEF_ELEVATION=45 ;elevation angle to be used for calculating shaded relief product

NETVOLC Volcano Sample Parameters (volcanoes.txt) From WV01_20110224 (Cape Crozier)

[cone] [long (m)] [lat (m)] [x (m)] [y (m)]

CC_008 -1334171.2168 251439.3755 580 550 CC_018 -1339022.9489 255063.0610 550 550

177

Appendix C: Morphometric Parameters

Key to Morphometric Parameters

Symbol (unit) Name Description

2 AB (km ) Basal area Planimetric area of the edifice outline

WB (m) Basal width Average width of the edifice base calculated as SQRT(AB/π)*2

MAxB Major basal axis Length of the maximum base diameter passing through the centroid HMAX (m) Maximum height Difference between the summit elevation and the elevation of the lowest point of the edifice outline

178

HIDW (m) IDW mean height Difference between the summit elevation and the elevation of the 3D IDW basal surface of the cone Volume enclosed between the DEM surface of the edifice and a horizontal base with elevation equal to the lowest edifice V (km3) Maximum volume MAX outline point 3 VIDW (km ) IDW mean volume Volume enclosed between the DEM surface of the edifice and the 3D IDW basal surface ei Main flank ellipticity index Measure of the elongation of the main elevation contours that enclose the edifice ii Main flank irregularity index Measure of the complexity of the main elevation contours that enclose the edifice

eiAVG Mean ellipticity index Mean of all ei values

iiAVG Mean irregularity index Mean of all ii values

H/WB Height/basal width ratio Measure the overall steepness of the edifice

WS/WB Summit width/basal width ratio Measure of the relative size of the summit region

SMIN (º) Minimum slope Mean slope of the height interval with minimum average slope value

SMAX (º) Maximum slope Mean slope of the height interval with maximum average slope value

STOT (º) Mean slope Mean slope of the entire edifice

178

(continued) Symbol (unit) Name Description

SσTOT (º) Mean slope standard deviation Standard deviation of mean slope of the edifice

SFL (º) Mean flank slope Mean slope of the edifice excluding the summit region

SσFL (º) Mean flank slope standard deviation Standard deviation of mean slope of the flank

SS (º) Mean summit slope Mean slope of the summit region

SσS (º) Mean summit slope standard deviation Standard deviation of the mean slope of the summit region

ESMAX (m) Maximum slope elevation Elevation of height interval with mean maximum slope

HSMAX Maximum slope height fraction Fraction of height relative to HMAX at which the maximum mean slope occurs

SSMAX (º) Mean maximum slope Mean slope of the height interval with the maximum average slope

αS (º) Maximum basal axis through summit Azimuth of major basal axis passing through summit point

αB (º) Maximum basal axis through base Azimuth of major basal diameter passing through base centroid

αMAX (º) Maximum basal axis orientation Azimuth of the axis of maximum basal width that passes through any point

179 αFL (º) Mean flank azimuth Average azimuth of maximum diameters of main elevation contours on edifice flank

179

Morphometric Parameters

Age A W MAx H H V V S S S Sσ S Sσ Sσ ES SS α α α α Cone ID Error Glac. B B B MAX IDW MAX IDW ei ii ei ii H/W W /W MIN MAX TOT TOT FL FL S (º) S MAX HS MAX S B MAX FL (Ma) (km2) (m) (m) (m) (m) (km3) (km3) AVG AVG B S B (º) (º) (º) (º) (º) (º) S (º) (m) MAX (º) (º) (º) (º) (º) MM_109 0.060 0.08 N 0.4038 717 846 208 78 0.0410 0.0068 1.39 1.63 2.19 1.05 0.109 0.003 0.00 68.09 20.63 9.79 20.63 9.79 18.29 7.60 1728 0.992 26 169 16 168 137

MM_022 0.120 0.02 N 0.3384 656 836 122 73 0.0230 0.0068 1.62 1.53 2.48 1.16 0.111 0.191 0.00 72.11 20.02 10.08 19.43 9.78 27.20 10.74 785 0.769 23 62 35 46 41

MM_003 0.170 0.10 N 0.0118 122 148 34 18 0.0002 0.0001 1.46 1.41 1.25 1.05 0.143 0.548 0.52 53.63 22.32 9.53 24.54 8.43 16.23 9.73 462 0.738 29 9 18 91 166

RS_060 0.196 0.09 N 0.0263 183 211 68 38 0.0010 0.0003 1.33 1.33 2.17 1.30 0.206 0.069 0.70 64.52 27.78 11.05 27.82 11.05 20.77 8.26 1480 0.785 30 166 103 97 21

MS_001 0.230 0.22 N 0.2416 555 635 225 74 0.0356 0.0067 1.31 1.25 4.22 1.35 0.134 0.060 0.00 74.56 25.46 11.62 25.51 11.61 16.02 9.52 942 0.915 32 8 11 11 84

MM_068 1.060 0.02 N 0.4898 790 952 200 150 0.0453 0.0219 1.45 1.62 1.73 1.30 0.190 0.335 0.00 78.52 24.41 11.88 24.22 11.81 25.85 12.27 790 0.533 32 23 17 25 160

MM_510 1.230 0.03 N 0.0537 261 374 107 39 0.0032 0.0006 2.05 1.48 5.87 2.28 0.148 0.142 0.00 65.20 25.34 10.50 25.53 10.46 16.09 7.96 1516 0.959 19 4 5 2 161

RS_008 1.261 0.04 N 0.7196 957 1071 245 140 0.1011 0.0284 1.25 1.49 3.08 1.25 0.146 0.111 0.00 76.09 21.72 11.49 21.79 11.50 15.66 8.23 520 0.946 19 33 38 31 3

RS_080 1.650 0.30 N 0.0173 148 183 45 20 0.0004 0.0001 1.52 1.37 1.64 1.13 0.132 0.096 0.56 50.72 19.72 6.71 19.74 6.68 18.27 9.84 546 0.901 26 42 141 41 13

RS_079 1.830 0.09 N 0.1455 430 528 71 38 0.0054 0.0015 1.50 1.39 3.59 1.55 0.088 0.163 0.00 53.19 15.71 7.18 15.74 7.16 14.61 7.79 546 0.915 17 11 31 30 164

180 MB_039 1.990 0.03 N 0.2740 591 705 83 55 0.0105 0.0035 1.43 1.40 3.11 1.87 0.093 0.343 0.00 70.13 18.25 9.96 16.77 9.06 24.04 11.15 682 0.628 24 10 180 11 77

RS_014 2.440 0.16 N 0.0141 134 169 24 17 0.0002 0.0001 1.60 1.32 1.95 1.15 0.129 0.172 0.21 42.42 18.41 7.57 18.72 7.44 9.56 5.44 500 0.775 21 66 84 55 82

BP_010 2.700 0.09 N 0.6169 886 930 144 88 0.0497 0.0188 1.10 1.11 3.18 1.79 0.099 0.295 0.11 67.46 19.23 9.24 19.67 9.20 14.61 8.32 270 0.865 21 24 29 29 3

MM_507 3.070 0.08 N 0.1661 460 603 133 55 0.0131 0.0025 1.72 1.43 2.84 1.32 0.119 0.104 0.08 65.95 19.51 7.72 19.60 7.67 11.31 7.49 1914 0.978 15 143 6 173 65

BI_010 3.350 0.14 N 0.6053 878 977 158 127 0.0395 0.0225 1.24 1.36 1.64 1.16 0.144 0.094 0.03 67.22 18.77 9.87 18.75 9.87 21.08 10.05 696 0.896 27 36 49 44 67

MD_049 4.100 0.11 N 0.1592 450 565 56 43 0.0048 0.0025 1.57 1.30 2.30 1.57 0.095 0.339 0.06 62.30 15.38 8.77 15.78 8.81 12.23 7.82 522 0.726 18 29 29 31 7

MB_075 4.880 0.68 N 0.2227 533 621 117 55 0.0164 0.0045 1.36 1.35 1.71 1.26 0.103 0.050 0.00 71.49 20.31 8.94 20.33 8.94 12.86 5.51 646 0.961 13 92 133 108 27

MB_076 5.370 0.48 N 0.0847 328 407 59 24 0.0022 0.0003 1.53 1.33 2.34 1.41 0.073 0.081 0.00 64.66 16.49 9.47 16.46 9.47 21.16 9.18 534 0.860 24 85 88 86 177

MB_079 5.730 0.25 N 0.1266 401 476 70 40 0.0061 0.0022 1.41 1.49 2.25 2.16 0.100 0.340 0.30 56.41 19.00 7.96 19.54 7.88 14.90 7.29 662 0.917 16 23 30 31 44

MB_005 7.310 0.23 N 0.2083 515 666 86 52 0.0074 0.0025 1.67 1.43 1.89 1.18 0.101 0.098 0.03 67.47 18.10 9.71 18.14 9.72 13.22 6.97 738 0.820 22 118 111 111 168

MB_015 7.500 0.30 N 0.1156 384 546 108 39 0.0067 0.0007 2.03 2.14 1.44 1.24 0.101 0.058 0.19 69.31 19.92 10.36 19.94 10.37 13.08 7.23 806 0.963 29 146 98 109 85

BI_022 9.020 0.07 N 0.9494 1099 1193 164 51 0.0954 0.0095 1.18 1.71 2.54 1.55 0.046 0.074 0.05 67.87 16.27 8.75 16.29 8.75 11.30 7.33 606 0.965 12 126 125 125 130

180

(continued)

Age A W MAx H H V V S S S Sσ S Sσ Sσ ES S α α α α Cone ID Error Glac. B B B MAX IDW MAX IDW ei ii ei ii H/W W /W MIN MAX TOT TOT FL FL S (º) S MAX HS MAX S B MAX FL (Ma) (km2) (m) (m) (m) (m) (km3) (km3) AVG AVG B S B (º) (º) (º) (º) (º) (º) S (º) (m) MAX (º) (º) (º) (º) (º) ME_014 0.033 0.01 Y 0.0320 202 240 93 46 0.0020 0.0005 1.42 1.27 1.37 1.07 0.229 0.074 0.34 71.21 30.50 13.14 30.57 13.13 18.20 8.24 1770 0.977 24 63 91 93 137

HP_001 0.348 0.01 Y 0.1061 368 414 84 43 0.0056 0.0012 1.27 1.23 3.09 1.32 0.117 0.076 0.00 51.50 20.46 9.40 20.50 9.39 17.54 9.72 246 0.955 23 24 91 96 85

DI_410 0.775 0.02 Y 0.2522 567 652 101 93 0.0090 0.0069 1.32 1.27 1.44 1.15 0.164 0.239 0.00 61.00 20.83 10.25 21.46 10.02 10.45 8.28 18 0.745 30 12 14 25 21

RS_027 0.853 0.05 Y 0.2427 556 608 147 48 0.0213 0.0031 1.20 1.21 2.27 1.07 0.087 0.003 0.00 72.56 20.22 10.52 20.22 10.52 23.23 10.49 1888 0.996 26 144 33 41 90

HP_010 1.000 0.15 Y 0.1191 389 446 99 49 0.0061 0.0013 1.31 1.18 1.91 1.17 0.126 0.112 0.00 55.86 18.23 8.65 18.23 8.64 18.35 8.95 236 0.934 19 81 91 88 10

CC_018 1.290 0.05 Y 0.4920 791 839 218 149 0.0540 0.0214 1.12 1.14 1.36 1.29 0.188 0.293 0.00 69.98 24.25 11.99 24.85 11.97 17.87 10.16 300 0.770 35 171 37 38 61

CC_008 1.310 0.04 Y 0.4087 721 785 196 100 0.0455 0.0088 1.19 1.22 1.43 1.25 0.138 0.055 0.00 71.42 24.33 10.60 24.36 10.60 14.97 7.99 304 0.957 26 16 55 54 30

WI_013 2.110 0.05 Y 0.1640 457 564 95 50 0.0102 0.0021 1.52 1.49 3.04 1.85 0.109 0.519 0.11 57.47 16.75 9.38 17.42 9.41 14.89 9.03 600 0.767 11 36 38 38 16

BP_017 2.250 0.05 Y 1.5498 1405 1478 315 159 0.3023 0.0963 1.11 1.10 3.82 1.62 0.113 0.167 0.00 78.02 23.58 12.29 23.71 12.35 20.30 10.16 748 0.939 21 66 102 93 58

WI_045 3.290 0.10 Y 0.6261 893 1005 117 58 0.0497 0.0158 1.27 1.14 2.72 1.92 0.065 0.282 0.00 51.96 12.96 6.74 13.18 6.73 10.44 6.35 264 0.865 23 85 88 88 2

MR_003 3.700 0.20 Y 0.4120 724 778 246 87 0.0600 0.0124 1.15 1.22 1.80 1.56 0.121 0.160 0.00 66.11 22.79 9.29 23.10 9.17 11.31 6.16 288 0.936 16 93 5 7 21

181 WI_007 4.603 0.18 Y 1.3770 1324 1328 272 113 0.1872 0.0393 1.11 1.12 2.25 1.27 0.085 0.021 0.00 62.52 15.08 7.07 15.08 7.07 11.92 6.62 662 0.925 22 13 89 89 26

WI_036 5.040 0.31 Y 0.8516 1041 1096 420 109 0.2209 0.0216 1.11 1.16 2.06 1.23 0.105 0.185 0.00 71.76 22.69 10.07 22.89 10.07 16.99 8.16 420 0.912 12 144 16 13 30

MB_065 8.090 0.12 Y 0.1482 434 547 102 49 0.0075 0.0017 1.59 1.30 1.38 1.15 0.114 0.060 0.00 64.78 19.83 8.63 19.84 8.63 15.39 8.15 778 0.888 23 55 39 40 168

MB_060 8.319 0.35 Y 0.8013 1010 1144 190 34 0.0638 0.0025 1.28 1.34 3.76 1.02 0.033 0.002 0.00 60.61 15.85 7.73 15.85 7.73 13.42 4.29 580 0.994 13 41 53 53 138

BI = Black Island MB = Minna Bluff MM = Mount Morning BP = Brown Peninsula MD = Mount Discovery MS = Mason Spur CC = Cape Crozier ME = Mount Erebus RS = Royal Society Range DI = Dailey Islands MR = Mount Bird WI = White Island HP = Hut Point

181

182

Figure 66. EVP map showing cone locations, age, and ID labels, corresponding to Appendix C table of morphometric parameters. 182