Periglacial and Glacial Landform Mapping in the Las Veguitas Catchment, Cordillera Frontal of the Andes (Argentina)

Home , Dry Andes, Glacial landform, Ice field, Landform, Rock glacier

Department of Physical Geography

Periglacial and glacial landform mapping in the Las Veguitas catchment, Cordillera Frontal of the Andes (Argentina)

Eirini Makopoulou

Master’s thesis NKA 211 Physical Geography and Quaternary Geology, 60 Credits 2018

Preface

This Master’s thesis is Eirini Makopoulou’s degree project in Physical Geography and Quaternary Geology at the Department of Physical Geography, Stockholm University. The Master’s thesis comprises 60 credits (two terms of full-time studies).

Supervisors have been Peter Kuhry at the Department of Physical Geography, Stockholm University and Dario Trombotto at the Geocryology, CONICET, Mendoza (Argentina). Examiner has been Johan Kleman at the Department of Physical Geography, Stockholm University.

The author is responsible for the contents of this thesis.

Stockholm, 12 June 2018

Lars-Ove Westerberg Vice Director of studies

Abstract

The semi-arid and arid Andes of South America are characterized by large areas with glacial and periglacial environments. This study focusses on the distribution of glacial and periglacial landforms in the Las Veguitas catchment, Cordillera Frontal, Argentina. A detailed geomorphological map of the Las Veguitas catchment is presented, based on high-resolution elevation data (ALOSPALSAR), satellite imagery (Landsat 8, World View 2, Google Earth), and field studies. First, a general topographical analysis is performed for the entire Las Veguitas catchment, including elevation, slope and aspect characteristics. Second, the altitudinal range of glacial features (glaciers, debris covered glaciers and thermokarst ponds on glaciers) and the altitudinal range and predominant aspect of periglacial features (active, inactive and fossil rock glaciers) are analyzed. Currently, glaciers are restricted to ≥ 4300m, but moraines are identified to elevations of c. 3200m. Active rock glaciers extend down to c. 3450m and have a more southern aspect then both inactive and fossil rock glaciers. Third, a temporal analysis has been performed of glacier and rock glacier flow using a time series of remote sensing images. Glacier flow traced by the displacement of thermokarst lake features (2006-2016) had a mean velocity of 6.66m/yr. The mean velocity of rock glaciers (1963-2017) was much lower at 0.63m/yr. Finally, the thesis discusses limitations and uncertainties in study methods and suggestions for further research activities.

Keywords: geomorphological map, glaciers, thermokarst lakes, mountain permafrost, rock glaciers, Argentinean Andes, remote sensing images, ArcGIS, spatial and temporal analyses

Contents

1 Introduction ...... 5 2 Background ...... 7 2.1 The Cordillera de los Andes ...... 7 2.2. Glacial history in the Central Andes ...... 8 2.3 Glacial Processes and landforms ...... 9 2.4 Periglacial Processes and landforms ...... 11 3 Study area...... 15 3.1 Geology ...... 15 3.2 Climate ...... 16 3.3 Vegetation cover ...... 17 3.4 Permafrost distribution ...... 17 4 Material and Methods ...... 17 4.1 Pre-field preparatory steps ...... 19 4.2 Fieldwork ...... 20 4.3 Final processing ...... 21 4.4 Temporal analysis ...... 22 5 Results ...... 23 5.1 Topography Maps ...... 23 5.2 Land cover and SAVI maps ...... 25 5.3 The geomorphological map ...... 25 6 Spatial and temporal analyses ...... 27 6.1 Topographic analysis ...... 27 6.1.1 Elevation, slope and aspect...... 27 6.1.2 Landform coverage ...... 29 6.1.3 Altitudinal distribution of current glacial features ...... 29 6.1.4 Altitudinal distribution and aspect of rock glaciers ...... 31 6.2 Temporal Analysis ...... 33 6.2.1 Thermokarst lake displacement in debris covered glacier (2006-2016)...... 33 6.2.2 Stepanek and Franke rock glacier flow (1963-2017) ...... 35 7 Discussion ...... 37 8 Conclusions ...... 39

9 Limitations and further research ...... 40 Acknowledgments...... 41 References ...... 42 Appendix ...... 45

1 Introduction

The Central Andes of South America between Santiago, Chile and Mendoza, Argentina, consists of three major parts: the Cordillera Principal, the Cordillera Frontal, and the Precordillera. The Argentinean Andes have abundant mineral resources that attract mining (Angillieri, 2016). Many deposits are located at higher elevations in periglacial environments. High altitudes in combination with low mean annual air temperature are the main factors for Andean permafrost (Trombotto, 2000). Table 1 includes variable information about the climate, the types of landforms, and the geographic region for every mountain permafrost zone along the Cordillera de los Andes (Garleff and Stingl, 1986). In Argentina, the presence of continuous permafrost depends on topography and a mean annual temperature of -2o C to -4oC. At 33o S, it is found at > 4200m. The discontinuous permafrost zone can be identified by the presence of rock glaciers (Barsch, 1977). Currently, the lower permafrost limit in the Central Andes is generally found at an elevation of 3700-3800m (Trombotto, 2000). The term island permafrost was introduced for landform features found as isolated patches at c. 4000m and relict permafrost is represented by frozen ground at elevations as low as 3400m, predominantly in rock glaciers (Trombotto, 2000). Knowledge about the spatial distribution of rock glaciers and permafrost is important for studies that include the environment and water management, because rock glaciers are stores of frozen water (Brenning, 2008). In the high Andes of Argentina and Chile, glacial and periglacial processes have been studied since the 1970s (Corte, 1976; Wayne, 1984; Lothar, 1996; Trombotto 2000; Trombotto et al., 1999, 2004; Trombotto and Borzotta, 2009; Azocar, 2010; Angillieri, 2016). Knowledge of landforms, surface processes, and material distribution supplies critical information for land practices, especially in dynamic and complex mountainous areas (Barsch et al., 1987). A geomorphological map should contain information about lithology, morphography, structure, hydrography, age, and process or genesis (Gustavsson et al., 2006). This thesis aims to visualize and understand the landscape and its dynamics in the area of Las Veguitas, Central Andes, by mapping glacial and periglacial landforms. The general description of the geomorphology in this region has been presented by Wayne (1984), and hydrological, geomorphological, and global warming observations have been published by Trombotto and Borzotta (2009). The present study uses high resolution elevation (ALOSPALSAR) and spectral data (World View 2) to map landforms and a detailed geomorphological map has been produced. Temporal dynamics of the main glacial and

5 periglacial features are assessed using a time series of remote sensing images (1963/2006 to 2016/2017), using statistical techniques with a combination of terrain attributes and remote sensing variables. Maps can be easily digitized, analyzed and reproduced in GIS (Geographic Information Systems), but fieldwork remains the basis of a detailed geomorphological map. With the technical approaches offered by digital remote sensing and GPS-localized field observations, the geomorphological mapping can be more accurate. The detailed geomorphological map of the Las Veguitas catchment is the first of its kind for the Central Andes near Mendoza. Furthermore, the spatial distribution of mountain permafrost features will be used to assess the soil organic carbon storage in Andean periglacial environments, for which a field inventory was conducted in parallel to this study.

Table 1: Permafrost zones in the Andes, adapted from Trombotto (2000) and Garleff and Stingl (1986).

Permafrost Tropical Andes Dry Andes Central Andes Southern zones (17o-31oS) (31O-35OS) Andes

Continuous Chimborazo, NW Argentina, -2/-4 oC, 500- Ecuador, -1/-2 oC, 900mm/yr (6275m) <300mm/yr Discontinuous Active rock Rock glaciers, Active rock Active rock glaciers >175mm/yr glaciers glaciers (Barsch, 1977) Sporadic Rock glaciers Rock glaciers

Island Chimborazo, Cryobasin, (Isolated Ecuador, with patches) <5000m cryosediments

Degraded Rock glacier, ice temp. -1.6 oC

Relict Salt lakes in the Rock glaciers Atacama and Altipano

The specific objectives and aims of this thesis are to:

 Create a comprehensive geomorphological map for the study area by mapping the glacial and periglacial landforms by using satellite images, a digital elevation model (DEM) and field observations  Perform a topographic analysis of the study area by processing the DEM and create new datasets on slope and aspect  Characterize the altitudinal distribution and aspect of the main glacial and periglacial landforms  Conduct a temporal analysis of landform dynamics using an aerial photograph from 1963 and compare it with current remote sensing data

2 Background 2.1 The Cordillera de los Andes

The Andes extend along the western side of South America and were created by plate tectonic processes caused by the compression of the western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate (Ollier and Pain, 2000). The range is roughly 9000 km long and up to 750 km wide, elevation is in excess of 6000m, and the range can be divided into three parts (Fig. 1):

1. The Southern Patagonian Andes, from Tierra del Fuego to Gulf of Penas 2. The Central Chilean-Peruvian Andes, from the Gulf of Penas to Amotape 3. The Northern Colombian-Venezuelan Andes, from Amotape to the Caribbean Arc

The evolution of the central Andes as described by Summerfield (1991), has been continuous subduction since the Mesozoic. During an episode of mountain building that happened in the Late Cretaceous – Early Cenozoic to the east of the earlier orogeny a period of emplacement of granite intrusions occurred resulting in the development of the Western Cordillera. Another consequence of this, was the transmission of compressive stresses to the East where the Eastern Cordillera was folded and uplifted. In the Pliocene-Miocene, emplacement of magma caused intense folding and the formation of thrust sheets in the Eastern Cordillera. High narrow ranges were formed when the Eastern Cordillera was pressed against 7 the Brazilian Shield, with the possible result of a change in the orientation of the Andes at Amotape.

Figure 1: Major structural and morphological divisions of the Andes (modified from A. Gansser, 1973).

" Because of copyright protection, this figure is missing in its electronic format.

See: Summerfield, M. A., 1991. Global Geomorphology, John Wiley and Sons, pg. 64, or the paper copy. "

2.2 Glacial history in the Central Andes

Clapperton (1983) summarized the glacial history of the Andes by the identification of moraine groups or drift units from glaciers, which have been assigned to the following periods: Holocene (10000 BP- present), the late glacial (ca. 16000-10000 BP), the last glaciation ‘late’ (ca. 30000-16000 BP), the last glaciation ‘middle and early’ (ca. 80000-30000 BP), the

8 penultimate glaciation (ca. 140000-170000 BP), and the pre-penultimate Pleistocene glaciations (<1.8-5 Ma BP). During the last 600 years glaciers have receded dramatically in almost all the Andes (Clapperton, 1983). Between the limits of the Little Ice Age glaciers and the moraines of the last glaciation a number of distinct groups of lateral and terminal moraines have been identified. In the Last Glaciation (ca. 30000-10000 BP), massive lateral-terminal moraine arcs are located at various distances down valley from the Holocene moraines. Morphologically, the moraines are fresh with sharp crests. The extent of Andean glacier expansion can be distinguished at two scales, the events dating to the Holocene and those developed in the Late Pleistocene (Clapperton, 1983), each glaciation inheriting a more eroded bed (deeper valleys and basins) than the previous one.

2.3 Glacial Processes and landforms

During the Pleistocene epoch, large sections of the earth’s surface in temperate latitudes were covered with huge continental ice sheets, and mountain ranges were sites of intense alpine glaciations at altitudes 1000m below present snowlines, but these glaciers melted away some 10.000 years ago and their impressions remain upon today’s landscape (Easterbrook, 1999). Glaciers are masses of ice and granular snow formed by compaction and recrystallization of snow, lying largely or wholly on land and showing evidence of past or present movement. Important parameters in this definition include the transformation of snow into ice to thicknesses great enough to promote motion (Easterbrook, 1999). Summerfield (1991) classified glaciers into six subtypes: ice dome, outlet glacier, ice field, cirque glacier, valley glacier and other small glaciers. In this study, cirque glaciers are most common (Fig. 2A). The movement of glaciers can be distinguished in two types of ice movement, internal deformation and basal sliding, the importance of these two mechanisms varies significantly with basal sliding accounting for up to 90% of the movement of warm-based glaciers, but being largely inoperative in cold-based glaciers Summerfield (1991). Two principal processes, abrasion and plucking (quarrying), are responsible for nearly all glacial erosion (Easterbrook, 1999). It is difficult to make an estimation of the rate of the glacial erosion processes. In the majority of glacial areas, traces of the pre-glacial surfaces are easily recognized and thus, post-Pliocene erosion can be easily recognized, however, in

9 continental glacial districts, traces of the pre-glacial surfaces appear to have been subjected to little alteration, while at the same time there is a complete absence of soil (Pavlopoulos et al. 2009). Summerfield, (1991) proposed that subglacial debris is transported along the base of a glacier, but glaciers also acquire supraglacial debris through material falling on to the ice surface from rock walls or other ice-free areas. Naturally, supraglacial debris is likely to be most abundant in valley and cirque glaciers and absent over large areas of ice sheets. Once it is buried, it becomes englacial debris and it can travel as such to the glacier snout (Easterbrook, 1999). Cirques (Fig. 2A) are characterized by steep headwalls that may vary from less than 100m to many hundreds of meter high (Easterbrook, 1999). Cirque development starts with the formation of a firn bank in a suitable depression, involving active frost weathering and mass movement processes promoted by the presence of meltwater around the firn bank. According to Summerfield (1991), the regular concave long profile form induces rotational sliding, and the flow lines are inclined away from the glacier surface near the headwall and towards the surface near the terminus. In order to maintain the ratio between height and length, deepening of the cirque floor must be accompanied by a retreat of the headwall. It has long been observed that the top layer of actively moving ice on a cirque glacier is usually separated from the headwall by a deep chasm known as a bergschrund (Summerfield, 1991). The physical characteristics of glacial sediments vary widely. Those deposited directly from glacial ice called till, are poorly sorted and not stratified, whereas those deposited from meltwater streams (outwash) or lakes (glaciolacustrine sediments) are sorted and stratified (Summerfield, 1991). Lateral Moraines (Fig. 2J & K), according to Summerfield (1991), are linear ridges of till formed by the accumulation of rock debris along the sides of a glacier. Most of the material is delivered to the moraine by ice movement, much of the rock debris in the lateral moraine is derived from rock falls and tributary streams from the valley sides above the glacier and is carried along the glacial margin until released by melting ice. Medial Moraines are formed when two tributary glaciers come together, the inside lateral moraines on each glacier no longer have a valley side against which to bank their lateral moraines, and they unite to form medial moraines that form ribbon like bands down-glacier (Easterbrook, 1999).

End Moraines are formed by the accumulation of rock debris at the terminus of a glacier. They are generally curvilinear in form, reflecting the shape of the glacier terminus and they are typically composed mostly of till, although bulldozed material and lenses of sand and gravel are not unusual (Easterbrook, 1999). Outwash Plains (Fig. 2J) are depositions of sand and gravel by meltwater streams beyond the margin of glaciers to produce flat, sloping plains. The plains slope away from the glacier because of the gradient of the meltwater streams that deposit the sediments (Easterbrook, 1999).

2.4 Periglacial Processes and landforms

The term ‘periglacial’ was introduced in 1909 by the Polish scientist Walery von Lozinski to describe the landforms and the processes occurring around the margins of the great Pleistocene ice sheets. Subsequently it was applied more broadly to encompass those processes and landforms associated with very cold climates in areas not permanently covered with snow or ice and in many cases located far from glaciers or ice sheets (Summerfield, 1991). Periglacial refers to non-glacial processes and landforms associated with cold climates, particularly with various aspects of frozen ground (Easterbrook, 1999). Washburn (1979) presented the classification of periglacial climates into four distinct categories:

1. Polar lowlands with mean temperature of the coldest month <-3 oC, ice caps, bare rock surfaces and tundra vegetation 2. Subpolar lowlands with mean temperature of the coldest month <-3 oC and the warmest month >10 oC which roughly coincides with tree-line in the northern hemisphere 3. Mid-latitude lowlands with mean temperature of the coldest month <-3 oC and mean temperature >10 oC for at least four months per year, which corresponds to taiga type of vegetation 4. Highlands where climate is influenced by altitude and latitude, and diurnal temperature ranges tend to be large

Periglacial processes, primarily freezing and thawing, are similar to those in temperate climates, but differ in their frequency and intensity. The effects of periglacial processes on the

11 landscape are not restricted to Polar Regions, also freeze-thaw occurs in areas beyond the permafrost regions and especially during the Pleistocene intense action of periglacial processes in mid-latitude regions accelerated hillslope development (Easterbrook, 1999). Solifluction (solum = soil, fluere = to flow) was described by Andersson (1906), who recognized its importance as a gradational agent in cold climatic regions where the soil is periodically saturated by the thawing of ice ground. Andersson (1906) defined the process as the flowing from higher to lower ground of masses of waste saturated with water (this may come from snow-melting or rain). Rock glaciers (Fig. 2D, E, F), according to Summerfield (1991), are tongue-shaped masses of angular boulders resembling in form a small glacier, they have a steep front, exceptionally exceeding 100m in height, which stands at the angle of repose of the constituent material. Rock glaciers are usually coming down from cirques or cliff-faces and may reach a length of 1km or more (Summerfield, 1991). According to Trombotto et al. (2004), an active rock glacier can be characterized as a mass of rock fragments and finer material, generally on a slope that contains either an ice core or interstitial ice and shows evidence of on-going movement. An example is the Stepanek rock glacier as shown in Fig 2D. On the other hand, an inactive rock glacier is a mass of rock fragments and finer material, on a slope that contains either an ice core or interstitial ice and shows evidence of past but not present movement (vegetated part of the Franke rock glacier, Fig. 2E). A fossil rock glacier can be defined as a former rock glacier area that has lost its ice content (lower part of the Infiernillo rock glacier, Fig. 2F). Thermokarst is a term used to describe topographic depressions formed by the thawing of ground ice (Summerfield, 1991). When these depressions are filled with water they form thaw lakes, also known as Thermokarst lakes (Black, 1969). In the Las Veguitas catchment, thermokarst lakes are found on the debris covered glaciers (Fig. 2B & C). Patterned ground is land in a periglacial region characterized by the surface material having distinct, symmetrical and geometric shapes (Easterbrook, 1999). Washburn (1956) developed a descriptive classification of patterned ground which emphasizes both the shape and degree of sorting of the materials. Five basic patterns are recognized: circles (Fig. 2G & I), nets, polygons, steps and stripes (Fig. 2H).

Figure 2: Glacial and periglacial landforms, illustrated by examples from the Las Veguitas catchment (Central Andes, Argentina).

3 Study area

The study area (Fig. 3) is located between 69o 22’ and 69o26’ W and 32o 57’ and 33o 00 S in the Cordon del Plata mountains, Cordillera Frontal, Argentina. The study area covers approximately 30 km2 and reaches heights of approximately 5500 meters above sea level. The highest peaks which are included in the study area are Cerro Rincon with 5420m, and Cerro Vallecitos with 5426m. The lower limit for the study area is 3000m, where the drainage of Las Veguitas catchment joins with the Rio Blanco river.

Figure 3: Location of the study area in South America (ArcMap Basemap) and satellite image of the Las Veguitas catchment (World View 2).

Sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. 3.1 Geology

The Cordillera Frontal contains a Paleozoic basement constituted by sedimentary, metamorphic and igneous rocks, which was strongly deformed during the Famatinian and Gondwanan orogenic cycles (Ramos, 1988) and is intruded by Upper Paleozoic granitoids. An 15

Andean cover lies over the Paleozoic basement and is constituted by Permo-Triassic and Cenozoic sedimentary, volcanic and volcanoclastic rocks, intruded by Mesozoic and Cenozoic granitoids (Rabassa and Clapperton, 1990). In the Las Veguitas study area there are quartzites and related metasediment rocks of volcanic origin, rhyolites and andesites and a few plutonic rocks. The southern part is composed of dark colorized quartzites, whereas the northern part is dominated by reddish-brown rhyolites (Wayne, 1984).

3.2 Climate

The study area belongs to Semi-Arid and Arid morphoclimatic zone with mean annual temperatures of -2 to 15oC and mean annual precipitation of 300-600mm and 0-300mm, respectively (Summerfield, 1991). According to Lliboutry (1998), conditions for areas with this type of climate are short lived summers and rigorous winters with low temperatures, scarce precipitation and strong winds. The closest meteorological station to the study area is “Vallecitos” at 2550m (32o 56’ S and 69o 23’ W). The mean annual air temperature was 6.3 oC between 1979-1994 and the mean annual precipitation 442mm between 1979-1983 (Trombotto et al. 2009). At the meteorological station Cristo Redentor, located at 3800m (32o 54’S and 70o 12’ W), scarse data are available for the period 1941 to 1984, with a mean annual temperature of -1.3o C, and mean monthly temperatures ranging from c. +4 to -7o C (Fig. 4).

Figure 4: Mean monthly temperatures at Cristo Redentor, based on 13 years of complete data for the period 1941 to 1984 (http://climexp.knmi.nl).

Mean monthly temperatures (1941-1984) 6,0

4,0

2,0

0,0 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun -2,0

-4,0

-6,0

-8,0

3.3 Vegetation cover

The study area is located at high altitude where the vegetation cover becomes limited. With the semi-arid and arid climate, the vegetation is represented almost exclusively by shrubs, grasses and cushion plants. Denser vegetation is only present in small wetland areas on outwash plains, slope fens and stable surfaces of Pleistocene moraines up to 3600m, above which vegetation becomes very scarse.

3.4 Permafrost distribution

The South American periglacial geomorphology is determined by cryogenic processes associated to Andean permafrost (Trombotto et al., 1997). Figure 5 shows the distribution of permafrost along the Cordillera de los Andes, based on modelling in combination with field evidence (Saito et al., 2016). In the Central Andes (31-35 oS), permafrost extends from the mountain tops down to elevations of c. 3500m. Periglacial processes that occur in the Las Veguitas study area are frost-related mass movement, solifluction, nivation, permafrost creep, and vertical and horizontal sorting. From these processes, the landforms that have been created are rock glaciers, solifluction lobes, and patterned ground (circles, stripes).

4 Material and Methods

Geomorphological mapping is a powerful scientific tool used to understand landscape configuration and development (Gustavsson et al., 2006). In order to map the geomorphological processes in the Las Veguitas catchment, an integrated analysis was carried out based on a digital elevation model (DEM), interpretation of satellite images and aerial photographs (Table 2), and field investigations (November 26-December 18, 2017). Observations were made on landforms, periglacial features and vegetation cover. Despite of the huge amount of high-resolution data on the Earth’s surface, the visual impression gained from the direct observations in the field remains invaluable. Though field mapping by its nature is subjective and affected by the skills (experience) of the mapper, it allows the mapper to become familiar with the landscape.

Figure 5: Latitude-altitude cross-section of current permafrost distribution in the Andes (adapted from Saito et al., 2016). Dark blue: continuous permafrost; light blue. Discontinuous permafrost; quadrangles: terminus of rock glaciers.

" Because of copyright protection, this picture is missing in its electronic format. See: https://onlinelibrary.wiley.com/doi/epdf/10.1002/ppp.1863 Saito, K., Trombotto, D.L., Yoshikawa, K., Mori, J., Sone, T., Marchenko, S., Romanovsky, V., Walsh, J., Hendricks, A. and Bottegal, E., 2015. Late Quaternary Permafrost Distributions Downscaled for South America: Examinations of GCM-based Maps with Observations.

Permafrost and Periglacial Processes, pg. 51. "

Table 2: Remotely sensed information and data used in this study.

Type Date Resolution Source WorldView 2 18-03-2017 0.5 cm Digital Globe

Landsat 8 26-01-2017 30 m U.S. Geological Survey (USGS) Aerial Photograph ?-?-1963 1:50000 Military Geographic Institute of Argentina DEM ?-?-2011 12.5 m Earth data Nasa (ALOS PALSAR) Satellite Imagery 03-06-2006, 2.5 m Google Earth 04-09-2010, 20-03-2016 According to Otto and Smith (2013), the production of good and purposeful maps in the field requires a clear definition of the aims and objectives. The mapping procedure included (1) pre-field preparatory steps, (2) the fieldwork and (3) final processing to produce the geomorphological map. Finally, (4) a temporal analysis of glacier and rock glacier flow could be performed based a time series of remote sensing images.

4.1 Pre-field preparatory steps

The first step before the field study was to obtain high resolution data for the Las Veguitas catchment. The Digital Elevation Model (DEM) was provided by Earth Data, NASA and downloaded from https://vertex.daac.asf.alaska.edu/. The DEM has a spatial resolution of 12.5 meters and it is constructed from Radar data which were geometrically and radiometrically corrected. The products created from the DEM are:

 a topographic map  a slope map  an aspect map  a preliminary landform map

All the maps and visualizations were produced in ArcMap 10.5, ArcGIS software and they are referenced to WGS-84 (World Geodetic System-84), using the UTM zone 19S (Universal Transverse Mercator), as a projected coordinate system. The study area was mapped in ArcMap 10.5 and with Google Earth Pro software (satellite imagery). All the landforms were digitized from Google Earth Pro imagery and then converted through ArcMap 10.5 into shape files for further analysis. The preliminary geomorphological map for the study area (glaciers, debris covered glaciers, rock glaciers, outwash plains, moraines, cirques, thermokarst lakes, colluvium and exposed bedrock) was prepared for a better understanding of the study area before the field trip. The criteria for the landform classification and identification are presented in Table 3, and are compatible with other geomorphological descriptions and previous studies (Barsch, 1977; Summerfield, 1991; Easterbrook, 1999; Trombotto et. al., 2004). A satellite image from Landsat 8 with resolution 30 meters spatial resolution was downloaded from https://earthexplorer.usgs.gov/. Based on this satellite image, the following preliminary products were developed:

 A land cover map  A Soil Adjusted Vegetation (SAVI) map

The satellite image was processed with ENVI 5.4 software and the product is a supervised land cover classification which includes Spectral Angle Mapper (SAM). The SAM method is a spectral classification technique that uses an n-D angle to match pixels to training data. This method determines the spectral similarity between two spectra by calculating the angle between the spectra and treating them as vectors in a space with dimensionality equal to the number of bands. Smaller angles represent closer matches to the reference spectrum. The pixels are assigned to the class with the smallest angle (Exelis, 2015). The selection of training data for the study area was based on Google Earth observation and the satellite image, which resulted in the identification of four different land cover types: snow- ice, barren ground, sparse vegetation, dense vegetation.

The Soil adjusted vegetation index (SAVI) is similar to NDVI but is used in areas where the vegetation cover is low and it uses the red and near infrared (NIR) spectral wavelengths to nearly eliminate the soil influences in vegetation indices (Huete, 1988). The equation is:

푵푰푹−푹푬푫 SAVI = ∗ (ퟏ + 푳) 푵푰푹+푹푬푫+푳 where “L” is a correction factor that ranges from 0 to 1. The value 0 is used when the area has very high vegetation cover and then it becomes the same equation as NDVI. The value is 1 for areas with very low vegetation. In this study, the value is 0.5 which is typically used for intermediate vegetation cover (Huete, 1988).

4.2 Fieldwork

The field trip took place from the 27th of November to the 17th of December 2017. During the field campaign the use of a hand-held GPS was helpful to localize ground truth observations. The main purpose was to check the preliminary maps that had been created. Tracks and waypoints from the study area show exactly the area that was covered in this field trip (Fig. 6). The sample points are located along transects selected for the soil organic carbon inventory in

20 the study area. At these sample points, detailed descriptions of land cover and landform types were made. Written notes and photos were also taken for better analysis.

Figure 6: GPS tracks and ground truth points from the fieldwork in the study area.

Sources: [Worldview 2] © [2018] DigitalGlobe, Inc.

4.3 Final processing

After fieldwork, a 1963 aerial photo (scale 1:50000) from the study area was obtained from Argentinean colleagues. Furthermore, a high resolution satellite image from WorldView-2 was acquired (spatial resolution of 50cm). The WorldView 2 image was georeferenced through ArcGIS with 7 Ground Control Points (GCPs), (Appendix, Fig. A1), a 1st Polynomial Order and a total Route Mean Square (RMS) error of about 2.92m, without the distortions in or warping of the image as caused by 2nd or 3rd Polynomial Orders. The interpretation of the landforms was performed with manual delineation, to create the final geomorphological map for the study area. An important step was the integration and comparison from GPS field data with the already existing data and products through ArcGIS software in order to validate remotely sensed observations.

The same procedure was followed for the georeferencing of the aerial photo from 1963. For the temporal analysis described below, it was necessary to georeference the photo two times, in different parts of the study area, because it had too many distortions and warps when the georeferencing was done for the whole area. These two separate procedures have been done for the two big rock glaciers in the study area (Stepanek and Franke). The algorithm that has been used is a 1st Polynomial Order, and the RMS errors are 1.6m and 7.8m for the Stepanek and Franke rock glaciers, respectively (Appendix, Fig. A2 & 3).

4.1.4 Temporal analysis

Glacier flow was traced through the displacement of thermokarst lakes in the debris covered parts of glaciers. The resolution of the aerial photo was not good enough to unambiguously recognize these features in 1963, instead this analysis has been done only through Google Earth imagery. The dates that the study area was without clouds and snow are (Appendix, Fig. A4):

 20/3/2016  9/4/2010  6/3/2006

By manual digitization from Google Earth and by exporting the data into ArcGIS, it has been possible to calculate the size from each thermokarst lake for these years. For the movement, the centroid has been calculated and then the distance between them between year of observation could be used to calculate the mean velocity of the glacier flow for each interval in meters per year. A similar procedure has been followed for the rock glaciers. However, in this case the 1963 aerial photograph and the 2017 satellite image could be used. For the two rock glaciers (Stepanek and Franke), the displacement of prominent ridges or lobes could be followed and again expressed as mean velocity of rock glacier flow in meters per year.

5 Results 5.1 Topography Maps

The topographic map (Fig. 7) reveals the relief of the area by contour lines that represent 100m elevation intervals. The slope map (Fig. 8) is based on the DEM (ALOSPALSAR), and includes seven classes: 0o-2o, 2o-5o, 5o-15o, 15o-20o, 20o-25o, 25o-35o and 35o-90o, which according to the IGU (International Geographical Union) is an acceptable way to visualize the slope characteristics of an area but always depends on the opinion of the interpreter. The slope algorithm from ArcMap was run on the elevation dataset. The steeper slopes are shaded red, whereas green represent the gentler slopes. The aspect map (Fig. 9) identifies the downslope direction of an area. It displays 45 o intervals, measured clockwise in degrees from 337.5o to 337,5o (the first interval being 337.5 o to 22.5 o, or North).

Figure 7: Topographic map of the study area

Figure 8: Slope map for the study area, created from the high resolution digital elevation model.

Figure 9: Aspect map of the study area, created from the high resolution digital elevation model.

5.2 Land cover and SAVI maps

The software ENVI 5.4 was used to develop the land cover classification (Fig. 10) and the Soil Adjusted Vegetation Index (Fig. 11) maps. The four main classes that were recognized in the study area are: Snow/Ice, Barren Land, Sparse Vegetation and Dense Vegetation. The Soil Adjusted Vegetation index (SAVI) minimizes the soil brightness.

Figure 10: Land cover classification map based on the Worldview 2 image.

5.3 The geomorphological map

The geomorphological map (Fig. 12) has been completed by combining the preliminary map, field work observations and the post mapping methods already described, using the following criteria for identifying and mapping glacial and periglacial features (Table 3).

Figure 11: Soil Adjusted Index (SAVI) map.

Figure 12: Geomorphological map of the study area (for larger printout, see Appendix Fig. A5).

Table 3: Identification criteria for the main landforms in the study area.

Feature Identification criteria

Glacier Perennial flowing ice masses, free of debris cover Debris covered Debris covered flowing ice masses, often found at the terminus glacier of a glacier Thermokarst lake, Melt ponds developed in the debris covered glacier glacier Active rock glacier Lobate or tongue-shaped body, perennially frozen ice, inclined front part Inactive rock glacier There is no movement, contains some perennial ice

Fossil rock glacier There is no movement, contains no perennial ice

Lateral moraine Linear ridges of till along the sides of a glacier Medial moraine Formed when two tributary glaciers come together by the inside lateral moraines Terminal moraine Ridges, generally curvilinear in form Outwash plain Depositions of sand and gravel by meltwater streams

Colluvium with Angular shaped rock material on the slopes and foothills of talus mountains, sometimes organized in distinct cones

6 Spatial and temporal analyses 6.1 Topographic analysis 6.1.1 Elevation, slope and aspect

The topographic analyses for this project are based on the DEM and the products that are derived from it (slope, aspect). Figure 13 shows the distribution of elevation as a cumulative proportion of the total study area (29.7 km2). Figure 14 shows the same graph, but for slope. Both lowest and highest elevations and gentlest and steepest slopes are under-represented in the study area. Figure 15 shows the predominant orientation of the study area, which is mostly northeast, east and southeast on account of its location on the eastern flank of the Cordillera Frontal.

Figure 13: Cumulative elevation distribution in the study area.

Elevation distribution 5500

5000

4500

Elevation 4000

3500

3000 0% 20% 40% 60% 80% 100% Cumulative area

Figure 14: Cumulative slope distribution in the study area.

Slope distribution 90

Slopes Slopes indegrees 30

0 0 20 40 60 80 100 Cumulative area %

Figure 15: Orientation of the study area.

Orientation of the study area N

NW NE

W E

SW SE

6.1.2 Landform coverage

Figure 16 shows the percent of the surface area in the Las Veguitas catchment (29.7 km2) occupied by the various recognized landform classes. Most of the study area (c. 71%) is characterized by exposed bedrock, located at high altitude, and colluvium on steeper slopes (often with talus features). Landforms of glacial origin, including perennial snow patch, glacier, debris covered glacier (with thermokarst lakes) and moraines, together occupy c. 18% of the area. The periglacial landform rock glaciers cover c. 9% of the Las Veguitas catchment, with the remaining c. 2% represented by outwash plains.

6.1.3 Altitudinal distribution of current glacial features

Figure 17 shows the altitudinal distribution of four types of current glacial landforms (perennial snow patch, glacier with exposed surface ice, debris covered glacier and thermokarst lake) within the study area. Glaciers and snow patches are found above c. 4180m, the debris covered glacier extends down to c. 4200m, with the thermokarst lakes on the debris covered glaciers confined to a narrow altitudinal range between c. 4350 and 4500m.

Figure 16: Landform percentage cover in the Las Veguitas catchment.

Landform cover percentage for the study area

Colluvium 36,93 Exposed Bedrock 34,17 Active rock glacier 7,17 Debris covered glacier 6,87 Lateral Moraine 4,02 Glacier 3,01 Perennial snowpatch 2,56 Outwash Plain 2,03 Inactive rock glacier 1,36 Fossil rock glacier 0,94 Medial Moraine 0,84 Terminal Moraine 0,06 Thermokarst lakes 0,04

0 5 10 15 20 25 30 35 40

Figure 17: Altitudinal distribution of the four types of current glacial features in the Las Veguitas catchment, showing mean, median, 1st and 3rd quartiles and min/max altitude for each landform class.

6.1.4 Altitudinal distribution and aspect of rock glaciers

A detailed analysis has been performed for the elevation and aspect of individual rock glaciers, where the larger rock glaciers have been subdivided into their active, inactive and fossil parts (Fig. 18). There are six larger rock glaciers with active, inactive and/or fossil parts (Stepanek, Franke, Infiernillo, A, B and C), The seven smaller rock glaciers are all considered active. Figures 19 and 20 show the distribution with elevation and the orientation of these rock glaciers (and their subdivisions).

Figure 18: Location of rock glaciers in the Las Veguitas catchment.

Most of the smaller active rock glaciers that exist in the study area are located at altitudes above 3900m, the only exceptions being the small rock glacier #7 (Figs. 18 and 19).

All the smaller rock glaciers have in common that they have a predominantly South to East aspect (Fig. 20) and that they are flanked on their northern side by steep mountain bedrock.

Figure 19: Altitudinal distribution of smaller active rock glaciers and larger rock glaciers (subdivided into active, inactive and fossil parts) in the Las Veguitas catchment. For coding see Figure 18.

Among the larger rock glaciers, the active part of Stepanek reaches the lowest elevation (terminus located at c. 3350m). This rock glacier is flanked on its northern and northeastern side by steep mountain bedrock (Fig. 18). As in the case with the smaller active rock glaciers, the active parts of the larger rock glaciers have often a southeastern component in their aspect (Fig. 20). The exception is the active part of Franke rock glacier (Fig. 18) with a northeastern aspect, but this is restricted to elevations of >4000m (Fig. 19) and for Infiernillo rock glacier between 3900 and 4100 meters. The fossil parts from the larger rock glaciers are located

32 between 3400 and 3900 meters (Fig. 19), except for the fossil part of rock glacier A (Fig. 18), which is located above 4000m (Fig. 19) and is oriented east to southeast. (Fig. 20). Figure 20: Orientation of rock glaciers, grouped into active, inactive and fossil parts of the larger rock glaciers, and the smaller active rock glaciers.

6.2 Temporal Analysis 6.2.1 Thermokarst lake displacement in debris covered glacier (2006-2016)

For the temporal analysis of glacier flow, the main focus has been the thermokarst lakes in the debris covered glacier of the upper, central valley (Figs. 12 and 21). In this study, thermokarst lakes were studied through a time series of Google Earth Worldview 2 images Digital Globe (Fig. A4). From 2006 to 2016, the number of thermokarst lakes have changed, but no trend is

33 apparent (Table 4). For the analysis of glacier flow, only five of these lakes were selected because they were persistent and could easily be recognized despite varying snow cover over the years of observation. Table 5 shows that the size of these thermokarst lakes, calculated by ArcGIS in hectares, has consistently increased over time.

Table 4: Number of thermokarst lakes on the debris covered glacier through the years 2006-2010-2016. Years 2006 2010 2016 Number of lakes 8 14 12

Table 5: Size of selected thermokarst lakes on the debris covered glacier through the years 2006-2010- 2016. No. lakes/Year 2006 (ha) 2010 (ha) 2016 (ha) 1 0,024 0,027 0,038 2 0,028 0,041 0,100 3 0,003 0,029 0,039 4 0,009 0,014 0,039 5 0,018 0,040 0,048

Figure 21 shows the change of location of the five selected thermokarst lakes over time. The centroid of each thermokarst lake was used to calculate the distance of displacement from 2006 to 2010 to 2016. From this, the velocity of glacier flow could be calculated (Table 6). There is no apparent trend over the (short) periods of observation. The average velocity of glacier flow over the period 2006-2016 is 6.66 m/yr.

Table 6: The velocity of glacier flow in m/yr deducted from the displacement of five thermokarst lakes for the years 2006, 2010 and 2016.

No. lake/Year 2006-2010 2010-2016 2006-2016

1 4.28 5.80 5.19 2 8.52 4.63 6.19 3 9.49 6.35 7.60 4 11.15 5.14 7.54

5 6.56 6.89 6.76

Figure 21: Displacement of five thermokarst lakes on the debris covered glacier between 2006-2016. Numbering refers to Tables 5 and 6.

Source: “Las Veguitas, Andes.” 32o 58´44.87´´ S and 69o 25´08.85´´ W. Google Earth Pro. March 20, 2016. Acquisition date: April 8, 2018.

6.2.2 Stepanek and Franke rock glacier flow (1963-2017)

The downward movement of the Stepanek and Franke rock glaciers was assessed by measuring the displacement of prominent ridges and lobes that could be recognized both in the 1963 aerial photograph and the 2017 satellite image. In order to increase accuracy, separate georeferencing was carried out based on fixed points within the vicinity of both rock glaciers. For the Infiernillo rock glacier, the georeferencing was not satisfactory enough. In the case of the rock glacier Stepanek, the RMS error from the georeferencing is 1,6m. Figure 22 shows the displacement of four distinct features between 1963 and 2017. The mean velocity of the Stepanek rock glacier over these 54 years has been 0.98 m/yr (Table 7).

Figure 22: Stepanek rock glacier flow between 1963 and 2017. Numbering refers to Table 7.

Table 7: Velocity calculations for Stepanek rock glacier.

No. of points Distance (meters) Velocity (m/yr.) 1 25.97 0.48 2 64.07 1.18 3 81.7 1.51 4 40.93 0.75

For the Franke rock glacier, the RMS error from the georeferencing is quite large, 7,8m. For the displacement and velocity calculations, three points have been taken into account (Figure 23 and Table 8). In this case, the mean velocity has been calculated to 0,28 m/yr. Due to the relative large RMS (compared to the actual calculated displacement) for the Franke rock glacier, velocities should only be considered approximate. 36

Figure 23: Franke rock glacier flow between 1963 and 2017. Numbering refers to Table 8.

Table 8: Velocity calculations for Franke rock glacier.

No. of points Distance (meters) Velocity (m/yr.) 1 14.10 0.26 2 17.94 0.33 3 13.95 0.25

7 Discussion

The studies that had been done so far for this part of the Andes mostly included larger areas in other catchments and they studied the glacial and periglacial environments in much less detail (Corte, 1976; Wayne, 1984; Lothar, 1996; Trombotto, 2000; Trombotto et al., 1999, 2004; Trombotto and Borzotta, 2009; Azocar, 2010; Angillieri, 2016). 37

The purpose of this study was the creation of a detailed geomorphological map for the Las Veguitas catchment in the Central Andes of Argentina. All landforms have been considered as separate, discrete forms. Statistical information has been extracted from these landforms. The produced map is one of a very few or even the first one with such a focus on the glacial and periglacial landforms in the Central Andes of Argentina. The study area can be seen as a representative case study for other catchments in this part of the Andes, characterized by the presence of cirque glaciers and frost weathered debris on top of the glaciers, rock glaciers and moraines. The glaciers in the Las Veguitas catchment are located at elevations above 4200m, the largest of them showing two well-developed cirques (Fig. 12). The lower part of this and other glaciers are debris covered glaciers (with some thermokarst lakes). These debris covered glaciers then grade into active rock glaciers that can be considered of glacigenic origin (Trombotto and Borzotta, 2009). The smaller active rock glaciers seem to have developed directly into slope materials. Considering the results from this and other studies carried out in this region of Argentina, it can be stated that rock glaciers have developed in areas with low mean annual temperature and low precipitation, steep slopes, intensive weathering, and extensive debris cover (Schrott et al., 2012). Most of the active rock glaciers in the study area are located well above 3400m. They are flanked by steep bedrock to the North and have a South to East orientation, which reduces incoming solar radiation. The lower part of the Las Veguitas central valley is characterized by the presence of lateral, medial and terminal moraines, which formed during former glacial advances. According to Mercer (1976), the Cordon del Plata had large glaciers extending as far down valley as 2600m during the last glaciation, which terminated c. 12.000 BP. In other parts of the study area such as La Cancha (4150m; see Fig. 12), solifluction lobes and patterned ground phenomena in the form of circles and stripes were recognized, which can be considered representative of active periglacial processes. At an altitude of c. 3500m relict sorted circles were observed. Although dating is lacking, these relict features can be assumed to have formed during the Little Ice Age (Clapperton, 1983). Remote sensing techniques, including Orthorectification, and image feature tracking were used in order to depict and measure the displacements of two larger rock glaciers in the study area by comparison of the aerial photo from 1963 with the Worldview 2 image. The calculated average speed in the Stepanek and Franke rock glaciers (0.98 and 0.28 m/yr,

38 respectively) are similar to those of rock glaciers in the Alps. For the latter, Barsch (1977) reported average speeds between 0.05-1.00 m/yr. Different stages of development can be observed in the Franke rock glacier. An active rock glacier grades into an inactive form (at c. 4000m), with at its foot a fossil part (at c. 3600m). These three types of a rock glacier can be differentiated relatively easy. The active part has multiple active ridges. In the inactive part, the surface has mainly stabilized and is already partially covered with vegetation. The fossil part is mainly characterized by a collapsed surface. Trends in the number and size of thermokarst lakes on debris covered glaciers were studied in the study area over the periods 2006-2010 and 2010-2016. No obvious trend was visible in the number of thermokarst lakes, which changed from 8 to 14 and then back to 12. However, the size of the lakes has increased over the years. This increase in size could be related to an increase in mean annual temperature observed for the region (Trombotto and Borzotta, 2009).

8 Conclusions

This study presents a detailed geomorphological map of the glacial and periglacial landforms in the high altitude study area of the Las Veguitas catchment, Cordillera Frontal, Andes, Argentina. The mapping is based on interpretation of satellite images (Worldview 2, Landsat 8, and Google Earth) and observations in the field. The high resolution Worldview 2 image provided a solid base for an accurate identification of landforms. Geographic Information Systems (GIS) and remote sensing are useful tools that allow the processing of a huge amount of data and the creation of new products for any particular study. However, the use of these two tools needs careful examination and some adjustments to the observations from the field. The main glacial and periglacial landforms that exist in the Las Veguitas catchment are cirques, glaciers, debris covered glaciers (with thermokarst lakes), rock glaciers (active, inactive and fossil), moraines and outwash plains. The glaciers are located between 4200 and 5100m, below well-developed cirques and they are facing mostly to the southeast, south and southwest. The debris covered glaciers are located mostly between 4200 and 4900m, with some thermokarst lakes at 4300 with 4500m, and a main orientation to north, northeast and east.

By measuring the change in location of five selected thermokarst lakes on debris covered glaciers over the years 2006, 2010 and 2016, the average velocity of glacier flow could be calculated to 6.66m/yr. Almost all active parts of rock glaciers that exist in the Las Veguitas catchment are located at altitudes above 3900m, with the exceptions being one small active rock glacier and the lower part of the large Stepanek rock glacier. This can be explained on account of their Southeast to South orientation. The active parts of rock glaciers with a more northern aspect, like the Franke rock glacier; are located at higher elevations. The rock glacier flow in the Las Veguitas catchment was calculated for the active parts of the Stepanek and Franke rock glaciers, with a mean velocity of 0.98 and 0.28 m/yr, respectively. The inactive parts of the large rock glaciers are generally located at elevations below 4000m, whereas the fossil parts from the larger rock glaciers are found between 3400 and 3900m.

9 Limitations and further research

The temporal analysis of glacier and rock glacier flow could have been more accurate, by having better-defined GCPs for the georeferencing of the aerial photo from 1963. The size of the thermokarst lakes has also been a major limitation for a better interpretation of satellite images or the aerial photograph, because in this area all the lakes were quite small without big amounts of water. Because the mapping system is still developing and Geographic Information Systems (GIS) are still improving, it is relevant to check the accuracy of the scale in the digital environment. An important factor about scale is when data from different sources are combined in the analysis (Gustavsson, 2006). Aerial photographs have lower radiometric quality and spatial resolution than the high-resolution satellite data (Worldview 2), and it is difficult to have accurate measurements from historical aerial photographs (Sannel and Brown, 2010). In this study, the aerial photograph from 1963 is a representative of medium data quality. The georeferencing of the photo could not be done at one and the same time for the whole study area because the RMS error and the distortion were too big. According to Gianinetto and Scaioni (2008) an acceptable RMS error for an aerial photograph should be ¼ of the scale. That means in this case that 1:50000 is 12.5m. In this study, for the three times that the aerial

40 photograph has been georeferenced, the RMS error was between 1 and 7m. It should also be mentioned that the study area is located in a high altitude and dynamic environment, with variable seasonal snow cover from year to year. Additionally, there are differences between each interpreter and how they decide to process the data. Future work in this type of mountain environment could have a similar approach but in other catchments of the Central Andes with a different predominant orientation. As it has been shown for rock glaciers, their distribution depends on elevation in combination with aspect. Also, a more detailed assessment in the study area with a focus on the periglacial processes and cryogenic structures would be very interesting. The use of radar or Lidar data for a detailed analysis of thermokarst on glaciers would be very interesting as there are not many studies of thermokarst lakes in the Central Andes. The analysis of rheological properties will aid in the understanding of the movement in landforms such as rock glaciers, talus slopes and solifluction lobes. Last, a search for techniques which can permit reliable, automated mapping of permafrost distribution would be great value for assessing the impacts of a changing climate on permafrost regions.

Acknowledgments

I wish to express my deepest gratitude towards my two supervisors Professor Peter Kuhry (Department of Physical Geography, Stockholm University) and Professor Dario Trombotto (Department of Geocryology, Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales, CONICET, Mendoza, Argentina) for their input and guidance. They gave me the opportunity to perform this field work in the Argentinean Andes and helped me with the analysis. I would also like to thank Mrs. Ivanna Pecker Marcosig and Mr. Didac Pascual, who accompanied me on this field trip, Dr. Karin Helmens who contributed with the design of the final geomorphological map, and last but not least, Dr. Ian Brown and Dr. Norris Lam for their support with remote sensing and GIS throughout this report. The field work and acquisition of aerial imagery was supported by the EU-JPI project on Constraining Uncertainties in the Permafrost Carbon Feedback (COUP).

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Appendix

Fig. A1a/b: Georeferencing of the Worldview 2 image: (a) selected points, (b) table with the points and the RMS error.

Fig. A2a/b: Georeferencing of the aerial photo for Stepanek rock glacier: (a) selected points, (b) the table with the points and the RMS error.

Fig. A3a/b: Georeferencing of the aerial photo for Franke rock glacier: (a) selected points, (b) the table with the points and the RMS error.

Fig. A4: Google Earth images for the temporal analysis of thermokarst lake displacement.

Source: “Las Veguitas, Andes.” 32o 58´44.87´´ S and 69o 25´08.85´´ W. Google Earth Pro. March 20, 2016. April 9, 2010. March 6, 2006. Acquisition date: April 8, 2018.

Fig. A5 (next page): Geomorphological map of the study area (larger printout)