DOCSLIB.ORG

Basaltic-Volcano Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Basaltic-Volcano Systems Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 Basaltic-volcano systems GEORGE P. L. WALKER Hawaii Center for Volcanology, Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, H196822, USA Abstract: This review and personal account of basaltic volcanism concentrates on the geological aspects and physical controls, unlike most others which concentrate on geo- chemistry. It serves as an update to reviews by Wentworth & Macdonald 20 to 40 years ago. The concept of volcanic systems is developed, a system including the plumbing, intrusions, and other accoutrements of volcanism, as well as the volcanic edifice. Five types of systems are described, namely lava-shield volcanoes, stratovolcanoes, flood-basalt fields, mono- genetic-volcano fields, and central volcanoes (having silicic volcanics as well as basaltic). It is postulated that the system-type depends on (a) the magma-input rate and (b) the frequency with which magma-batches enter the system (or modulation frequency). These controls determine whether a hot pathway is maintained from the source to the high-level magma chamber, and hence if eruptions are concentrated in the central-vent system. Reviews are given on many aspects: the different kinds of rift zones that volcanoes exhibit, and their controls; the mostly small intrusions, including coherent-intrusion complexes, that occur in and under the volcanic edifices; the great sill swarms that are an alternative to flood basalts; the origin of the craters and calderas of basaltic volcanoes; high-level magma chambers, their locations, and cumulate prisms; the positive Bouguer gravity anomalies that are attributed to cumulates and intrusion complexes; the structures of basaltic lava flows; the characteristics of basaltic explosive volcanism and the consequences of participation by non- volcanic water; the products of underwater volcanism; the origin and significance of joints, formed either by contraction or expansion, in volcanic rocks; and the distribution of vesicles in basaltic rocks. A fairly extensive bibliography is included. This is in part a review; it takes stock of changes Basaltic magma is derived by incongruent par- in concepts since the publications by Wentworth tial melting of mantle peridotite, favoured in & Macdonald (1953) and Macdonald (1967), tectonic settings (e.g. hotspots and rifts) where which were models of clear description of basal- mantle rock rises adiabatically to relatively shal- tic volcanics, and since the publication 12 years low levels, or in subduction-zone settings where ago of the landmark Basaltic Volcanism Study volatiles decrease the melting temperature of Project (1981). It also incorporates new ideas, mantle rock. new interpretations, and new ways of looking at Magma properties are basic parameters in the subject. The scope of basaltic volcanism is volcanology: too broad to cover all aspects, and petrology and geochemistry are specifically omitted. 9magma density relative to lithosphere density More than half of the world's volcanoes are makes volcanism possible and helps deter- basaltic or include basalt among their products; mine the positions of magma chambers and and about one third of known eruptions, involv- intrusions; ing about 20 volcanoes per year erupt basaltic 9viscosity and yield strength determine the geo- magma. Basaltic volcanoes occur in all tectonic metry and structures of lava flows and in- settings. Basaltic volcanism is associated with trusions; both divergent and convergent plate boundaries; 9gas content promotes eruptions and deter- it characterizes spreading ridges mostly con- mines their explosivity; and cealed beneath the ocean; it characterizes hot- 9gas content combined with viscosity and spot volcanism which, in oceanic settings, is rheology controls the explosive violence of almost exclusively basaltic and, in continental eruptions by determining the ease with which settings, is commonly bimodal (basaltic plus gases escape from magmas. rhyolitic); and it is widespread associated with Little mention is made of these basic magma andesitic and more silicic magmas in subduc- properties, because their values tend to be rather tion-zone settings, particularly where oceanic uniform amongst different basaltic volcanoes. lithosphere is subducted below oceanic or thin They are, thus, the unifying features of basaltic continental lithosphere, as in island arcs (e.g. the volcanism. More attention is therefore directed Mariana and Kurile arcs). at the influence of non-magmatic variables (e.g. From Prichard, H. M., Alabaster, T., Harris, N. B. W. & Neary, C. R. (eds), 1993, Magmatic Processesand Plate Tectonics, Geological Society Special Publication No. 76, 3-38. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 4 G. P. L. WALKER Fig. 1. Volcano types and volcano systems. (a) The five types of basaltic-volcano systems, illustrated schematically by block diagrams, b: basaltic vents; c: caldera; d: dyke; Is: lava shield of scutulum type; m: magma chamber; rz: rift zone; r: rhyolitic lava dome; s: sill or intrusive sheet; u: cumulates. (b) Time-averaged output rates of selected volcanic systems. W: equivalent world energy consumption by man (excluding food); C: equivalent energy consumption (including food) by city having a population of 1 million. (c) Inferred fields for the five volcanic-system types on a plot of modulation frequency against time-averaged output rate. (d) Sketch map of a moderate-sized flood-basalt field: Harrat Rahat in Saudi Arabia (Camp & Roobol 1989). Solid black: lavas of 10-1.7 Ma old; open diagonal shading with dots: lavas of 1.7-O.6 Ma old and their cinder cones; close diagonal shading: lavas of < 0.6 Ma old, including those of AD 641 and 1256; PC: Precambrian basement rocks; Qal: Quaternary sediments near Red Sea coast. (e) Sketch map of the Auckland monogenetic-volcano field, New Zealand, simplified by omitting the coastline (after Searle 1964). Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 BASALTIC-VOLCANO SYSTEMS 5 magma-supply rate and involvement of non- polygenetic structures commonly exceeding magmatic water) in causing most of the diver- 1000 km 3 in volume, and are not to be confused sity. with small monogenetic lava shields categorized by Noe-Nygaard (1968) as of scutulum type Volcano types and volcanic systems (Latin: scutulus, diminutive of scutus - 'shield') which have volumes of 0.1-15 km 3. Five volcano types are distinguished (Fig. la): lava-shield volcanoes, stratovolcanoes, flood Examples of lava-shield volcanoes Mauna Loa basalts, monogenetic volcanoes, and central vol- in Hawaii is the largest. It has an estimated canoes, this last having a significant proportion volume of 40000km 3, rises to 9-10km above of silicic products in addition to basalt. Flood the surrounding ocean floor and has a keel that basalt vents, as well as monogenetic volcanoes, projects well below it. Subaerial slopes are erupt once, and once only. Lava shields, strato- mostly 3-6 ~ except in the scars of old landslides. volcanoes and central volcanoes are polygenetic Pico in the Azores and Fogo in the Cape Verdes structures that erupt more than once. have steep (> 30 ~ cones atop the shield. Shields There is much merit in regarding volcanoes as in the Galapagos consist of an upwardly-convex parts of magmatic or volcanic systems. A system dome with slopes as steep as 30 ~ rising above the may embrace the intrusions, magma chambers, low-angle shield, and some of the eruptive conduits, magma source and accompanying fissures that occur on a narrow plateau around geothermal fields as well as the volcano itself. their large summit calderas are annular. Some The concept of volcanic systems acknowledges lava shields, notably Kilauea and perhaps also that the visible edifice of a volcano is only one Pico, consist mainly of pahoehoe. Others, such part of a bigger entity. as Mauna Loa, consist of roughly equal pro- A volcanic system may be compared with a portions of pahoehoe and aa. Others again, for system of civilization such as a city, with the example Madeira, Tutuila (Samoa) and the extensive infra-structure of transportation, water Galapagos volcanoes are composed mainly of and power supply, waste disposal and communi- aa. cations on which a city depends. Just as a vol- canic system is sustained by a supply of energy (in the form of hot magma), so a city system is Stratovolcanoes sustained by a supply of energy (in the form of These consist of a stratified succession of lava fossil fuels, electric power, and food). Very flows and interbedded pyroclastic deposits and roughly, a city of 1 million people requires about tend to have a conical form with a slope that the same power input as a volcanic system generally steepens upward until approximating having a magma input of 1 million m 3 per year. the repose angle (about 33-36 ~) of loose debris. Basaltic systems have a source in the mantle Most subduction-related basaltic volcanoes from which magma ascends, mainly because of conform with this type. Commonly the cone is its positive buoyancy but sometimes aided by truncated by a caldera. Rift zones tend to be tectonic forces, toward the surface. They have diffuse and ill-defined and grade into radial vent one or more conduits by which the magma systems, and cinder cones tend to be conspi- ascends. Polygenetic volcano systems generally cuous features on the volcano flanks. In many possess a high-level magma chamber, situated at arc volcanoes basaltic andesite and more silicic a neutral buoyancy level, which stores magma types accompany basalt. and modulates its delivery to the volcano and to sub-volcanic intrusions. Deep storage reservoirs Examples of stratovolcanoes The Japanese may also exist. island volcano of Izu-Oshima is representative of the arc-type basaltic cones. It has a basal Lava-shield volcanoes diameter of 27 km, rises about 2200 m above the ocean floor to 758 m above sea-level, and has a These consist mainly of lava flows and have volume of 415km 3 (Suga & Fujioka 1990) of the form of low-angle shields.
Load more

Recommended publications
  • Geologic Storage Formation Classification: Understanding Its Importance and Impacts on CCS Opportunities in the United States
    BEST PRACTICES for: Geologic Storage Formation Classification: Understanding Its Importance and Impacts on CCS Opportunities in the United States First Edition Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed therein do not necessarily state or reflect those of the United States Government or any agency thereof. Cover Photos—Credits for images shown on the cover are noted with the corresponding figures within this document. Geologic Storage Formation Classification: Understanding Its Importance and Impacts on CCS Opportunities in the United States September 2010 National Energy Technology Laboratory www.netl.doe.gov DOE/NETL-2010/1420 Table of Contents Table of Contents 5 Table of Contents Executive Summary ____________________________________________________________________________ 10 1.0 Introduction and Background
    [Show full text]
  • Hawaii Volcanoes National Park Geologic Resources Inventory Report
    National Park Service U.S. Department of the Interior Natural Resource Program Center Hawai‘i Volcanoes National Park Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2009/163 THIS PAGE: Geologists have lloongng been monimonittoorriing the volcanoes of Hawai‘i Volcanoes National Park. Here lalava cascades durduriingng the 1969-1971 Mauna Ulu eruption of Kīlauea VolVolcano. NotNotee the Mauna Ulu fountountaiain in the background. U.S. Geologiogicalcal SurSurvveyey PhotPhotoo by J. B. Judd (12/30/1969). ON THE COVER: ContContiinuouslnuouslyy eruptuptiingng since 1983, Kīllaueaauea Volcano contcontiinues to shapshapee Hawai‘Hawai‘i VoVollccanoes NatiNationalonal ParkPark.. Photo courtesy Lisa Venture/UniversiUniversitty of Cincinnati. Hawai‘i Volcanoes National Park Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2009/163 Geologic Resources Division Natural Resource Program Center P.O. Box 25287 Denver, Colorado 80225 December 2009 U.S. Department of the Interior National Park Service Natural Resource Program Center Denver, Colorado The National Park Service, Natural Resource Program Center publishes a range of reports that address natural resource topics of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Report Series is used to disseminate high-priority, current natural resource management information with managerial application. The series targets a general, diverse audience, and may contain NPS policy considerations or address sensitive issues of management applicability. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner.
    [Show full text]
  • Supplementary Material
    Supplementary material S1 Eruptions considered Askja 1875 Askja, within Iceland’s Northern Volcanic Zone (NVZ), erupted in six phases of varying intensity, lasting 17 hours on 28–29 March 1875. The main eruption included a Subplinian phase (Unit B) followed by hydromagmatic fall and with some proximal pyroclastic flow (Unit C) and a magmatic Plinian phase (Unit D). Units C and D consisted of 4.5 x 108 m3 and 1.37 x 109 m3 of rhyolitic tephra, respectively [1–3]. Eyjafjallajökull 2010 Eyjafjallajökull is situated in the Eastern Volcanic Zone (EVZ) in southern Iceland. The Subplinian 2010 eruption lasted from 14 April to 21 May, resulting in significant disruption to European airspace. Plume heights ranged from 3 to 10 km and dispersing 2.7 x 105 m3 of trachytic tephra [4]. Hverfjall 2000 BP Hverfjall Fires occurred from a 50 km long fissure in the Krafla Volcanic System in Iceland’s NVZ. Magma interaction with an aquifer resulted in an initial basaltic hydromagmatic fall deposit from the Hverfjall vent with a total volume of 8 x 107 m3 [5]. Eldgja 10th century The flood lava eruption in the first half of the 10th century occurred from the Eldgja fissure within the Katla Volcanic System in Iceland’s EVZ. The mainly effusive basaltic eruption is estimated to have lasted between 6 months and 6 years, and included approximately 16 explosive episodes, both magmatic and hydromagmatic. A subaerial eruption produced magmatic Unit 7 (2.4 x 107 m3 of tephra) and a subglacial eruption produced hydromagmatic Unit 8 (2.8 x 107 m3 of tephra).
    [Show full text]
  • Poroelastic Responses of Confined Aquifers to Subsurface Strain And
    Solid Earth, 6, 1207–1229, 2015 www.solid-earth.net/6/1207/2015/ doi:10.5194/se-6-1207-2015 © Author(s) 2015. CC Attribution 3.0 License. Poroelastic responses of confined aquifers to subsurface strain and their use for volcano monitoring K. Strehlow, J. H. Gottsmann, and A. C. Rust School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK Correspondence to: K. Strehlow ([email protected]) Received: 11 May 2015 – Published in Solid Earth Discuss.: 9 June 2015 Revised: 18 September 2015 – Accepted: 21 October 2015 – Published: 10 November 2015 Abstract. Well water level changes associated with mag- aquifer and are commonly neglected in analytical models. matic unrest can be interpreted as a result of pore pressure These findings highlight the need for numerical models for changes in the aquifer due to crustal deformation, and so the interpretation of observed well level signals. However, could provide constraints on the subsurface processes caus- simulated water table changes do indeed mirror volumetric ing this strain. We use finite element analysis to demonstrate strain, and wells are therefore a valuable addition to monitor- the response of aquifers to volumetric strain induced by pres- ing systems that could provide important insights into pre- surized magma reservoirs. Two different aquifers are invoked eruptive dynamics. – an unconsolidated pyroclastic deposit and a vesicular lava flow – and embedded in an impermeable crust, overlying a magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pres- 1 Introduction surization and the resulting hydraulic head changes as well as flow through the porous aquifer, i.e.
    [Show full text]
  • Abandonment of the Name Hartford Hill Rhyolitetuff and Adoption of New Formation Names for Middle Tertiary Ash-Flow Tuffs in the Carson City- Silver City Area, Nevada
    Abandonment of the Name Hartford Hill RhyoliteTuff and Adoption of New Formation Names for Middle Tertiary Ash-Flow Tuffs in the Carson City- Silver City Area, Nevada GEOLOGICAL SURVEY BULLETIN 1457-D Abandonment of the Name Hartford Hill Rhyolite Tuff and Adoption of New Formation Names for Middle Tertiary Ash-Flow Tuffs in the Carson City- Silver City Area, Nevada By EDWARD C. BINGLER CONTRIBUTIONS TO STRATIGRAPHY GEOLOGICAL SURVEY BULLETIN 1457-D UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1978 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Dingier, Edward C. Abandonment of the name Hartford Hill rhyolite tuff and adoption of new formation names for middle Tertiary ash-flow tuffs in the Carson City - Silver City area, Nevada (Contributions to stratigraphy) Geological Survey Bulletin 1457-D Supt. of Docs. No.: I 19.3: 1457-D Bibliography: p. D19 I. Geology, Stratigraphic-Tertiary. 2. Volcanic ash, tuff, etc.-Nevada- Carson City region. 3. Geology-Nevada-Carson City region. I. Title. II. Series. HI. Series: United States. Geological Survey. Bulletin 1457-D. QE75.B9 no. 1457-D [QE691] 557.3'08s [551.7'8] 78-606063 For sale by the Superintendent of Documents, U. S. Government Printing Office Washington, D. C. 20402 Stock Number 024-001-03124-8 CONTENTS Page Abstract___________________________________ Dl Introduction ______________________________________ 1 Acknowledgments ________________________________ 5 Ash-flow stratigraphy in the Carson City-Silver City area ___________ 7 Mickey Pass Tuff ________________________________ 7 Lenihan Canyon Tuff _____________________________ 8 Nine Hill Tuff _______________________________ 11 Eureka Canyon Tuff ______________________________ 14 Dacitetuff __________________________________ 16 Rhyolite tuff and augite rhyodacite tuff ___________________ 16 Santiago Canyon Tuff _____________________________ 17 References cited _____________________________^_____ 19 ILLUSTRATIONS Page FIGURE 1.
    [Show full text]
  • Flood Basalts and Glacier Floods—Roadside Geology
    u 0 by Robert J. Carson and Kevin R. Pogue WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES Information Circular 90 January 1996 WASHINGTON STATE DEPARTMENTOF Natural Resources Jennifer M. Belcher - Commissioner of Public Lands Kaleen Cottingham - Supervisor FLOOD BASALTS AND GLACIER FLOODS: Roadside Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington by Robert J. Carson and Kevin R. Pogue WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES Information Circular 90 January 1996 Kaleen Cottingham - Supervisor Division of Geology and Earth Resources WASHINGTON DEPARTMENT OF NATURAL RESOURCES Jennifer M. Belcher-Commissio11er of Public Lands Kaleeo Cottingham-Supervisor DMSION OF GEOLOGY AND EARTH RESOURCES Raymond Lasmanis-State Geologist J. Eric Schuster-Assistant State Geologist William S. Lingley, Jr.-Assistant State Geologist This report is available from: Publications Washington Department of Natural Resources Division of Geology and Earth Resources P.O. Box 47007 Olympia, WA 98504-7007 Price $ 3.24 Tax (WA residents only) ~ Total $ 3.50 Mail orders must be prepaid: please add $1.00 to each order for postage and handling. Make checks payable to the Department of Natural Resources. Front Cover: Palouse Falls (56 m high) in the canyon of the Palouse River. Printed oo recycled paper Printed io the United States of America Contents 1 General geology of southeastern Washington 1 Magnetic polarity 2 Geologic time 2 Columbia River Basalt Group 2 Tectonic features 5 Quaternary sedimentation 6 Road log 7 Further reading 7 Acknowledgments 8 Part 1 - Walla Walla to Palouse Falls (69.0 miles) 21 Part 2 - Palouse Falls to Lower Monumental Dam (27.0 miles) 26 Part 3 - Lower Monumental Dam to Ice Harbor Dam (38.7 miles) 33 Part 4 - Ice Harbor Dam to Wallula Gap (26.7 mi les) 38 Part 5 - Wallula Gap to Walla Walla (42.0 miles) 44 References cited ILLUSTRATIONS I Figure 1.
    [Show full text]
  • Insight Into Subvolcanic Magma Plumbing Systems Wendy A
    Insight into subvolcanic magma plumbing systems Wendy A. Bohrson Department of Geological Sciences, Central Washington University, 400 E. University Way, Ellensburg, Washington 98926, USA The Island of Hawaii, which is among the of CO2 inclusions (Bohrson and Clague, 1988; best-studied volcanic islands on Earth, provides Roedder, 1965). Rare gabbro from layer 3 of the lush ground for debates in volcanology that oceanic crust has also been identifi ed (Clague, focus on how magmatic systems evolve in space 1987a). Thus, a likely location for the deeper and time. Hawaiian volcanoes evolve through chamber is at the base of the oceanic crust. The four eruptive stages that are characterized by relatively low magma supply associated with distinct composition, magma supply rate, and the pre-shield and rejuvenated stages appar- Shallow magma plumbing degree of mantle melting (e.g., Clague, 1987a, ently precludes any persistent crustal magma system 1987b, and references therein). The pre-shield plumbing system; spinel lherzolite and garnet (shield stage) stage, fi rst identifi ed on Loihi Seamount (Moore pyroxenite xenoliths originate in the mantle et al., 1982), erupts mostly alkalic basalt and based on geobarometry, compositional charac- Deep basanite that refl ect a small magma supply and teristics, and other constraints (e.g., Frey and magma plumbing derive from relatively small degrees of mantle Roden, 1987; Frey, 1982). system melting. During the shield stage, tholeiitic Although rare on Hawaiian volcanoes, the (shield and post-shield stage) basalt (like that currently erupted at Kilauea more evolved compositions also provide insight and Mauna Loa) dominates, and refl ects com- into plumbing system dynamics.
    [Show full text]
  • The Magmatic Plumbing System of the Askja Central Volcano, Iceland, As
    PUBLICATIONS Journal of Geophysical Research: Solid Earth RESEARCH ARTICLE The magmatic plumbing system of the Askja central 10.1002/2016JB013163 volcano, Iceland, as imaged by seismic tomography Key Points: Tim Greenfield1, Robert S. White1, and Steven Roecker2 • Low velocities in the crust delineate the magmatic plumbing system 1Bullard Laboratories, University of Cambridge, Cambridge, UK, 2Rensselaer Polytechnic Institute, Troy, New York, USA beneath Askja volcano in Iceland • Primary magma storage region is at a depth of 5 km bsl but extends into the lower crust where melt movement Abstract The magmatic plumbing system beneath Askja, a volcano in the central Icelandic highlands, is generates microearthquakes imaged using local earthquake tomography. We use a catalog of more than 1300 earthquakes widely • Melt is distributed in discrete regions distributed in location and depth to invert for the P wave velocity (Vp) and the Vp/Vs ratio. Extensive synthetic throughout the crust to depths of over 20 km tests show that the minimum size of any velocity anomaly recovered by the model is ~4 km in the upper crust (depth < 8 km below sea level (bsl)), increasing to ~10 km in the lower crust at a depth of 20 km bsl. The plumbing system of Askja is revealed as a series of high-Vp/Vs ratio bodies situated at discrete depths Supporting Information: • Supporting Information S1 throughout the crust to depths of over 20 km. We interpret these to be regions of the crust which currently • Movie S1 store melt with melt fractions of ~10%. The lower crustal bodies are all seismically active, suggesting that • Movie S2 melt is being actively transported in these regions.
    [Show full text]
  • Ignimbrites to Batholiths Ignimbrites to Batholiths: Integrating Perspectives from Geological, Geophysical, and Geochronological Data
    Ignimbrites to batholiths Ignimbrites to batholiths: Integrating perspectives from geological, geophysical, and geochronological data Peter W. Lipman1,* and Olivier Bachmann2 1U.S. Geological Survey, Mail Stop 910, Menlo Park, California 94028, USA 2Institute of Geochemistry and Petrology, ETH Zurich, CH-8092 Zürich, Switzerland ABSTRACT related intrusions cooled and solidified soon shorter. Magma-supply estimates (from ages after zircon crystallization, as magma sup- and volcano-plutonic volumes) yield focused Multistage histories of incremental accu- ply waned. Some researchers interpret these intrusion-assembly rates sufficient to gener- mulation, fractionation, and solidification results as recording pluton assembly in small ate ignimbrite-scale volumes of eruptible during construction of large subvolcanic increments that crystallized rapidly, leading magma, based on published thermal models. magma bodies that remained sufficiently to temporal disconnects between ignimbrite Mid-Tertiary processes of batholith assembly liquid to erupt are recorded by Tertiary eruption and intrusion growth. Alternatively, associated with the SRMVF caused drastic ignimbrites, source calderas, and granitoid crystallization ages of the granitic rocks chemical and physical reconstruction of the intrusions associated with large gravity lows are here inferred to record late solidifica- entire lithosphere, probably accompanied by at the Southern Rocky Mountain volcanic tion, after protracted open-system evolution asthenospheric input. field (SRMVF). Geophysical
    [Show full text]
  • Hawaiian Volcanoes: from Source to Surface Site Waikolao, Hawaii 20 - 24 August 2012
    AGU Chapman Conference on Hawaiian Volcanoes: From Source to Surface Site Waikolao, Hawaii 20 - 24 August 2012 Conveners Michael Poland, USGS – Hawaiian Volcano Observatory, USA Paul Okubo, USGS – Hawaiian Volcano Observatory, USA Ken Hon, University of Hawai'i at Hilo, USA Program Committee Rebecca Carey, University of California, Berkeley, USA Simon Carn, Michigan Technological University, USA Valerie Cayol, Obs. de Physique du Globe de Clermont-Ferrand Helge Gonnermann, Rice University, USA Scott Rowland, SOEST, University of Hawai'i at M noa, USA Financial Support 2 AGU Chapman Conference on Hawaiian Volcanoes: From Source to Surface Site Meeting At A Glance Sunday, 19 August 2012 1600h – 1700h Welcome Reception 1700h – 1800h Introduction and Highlights of Kilauea’s Recent Eruption Activity Monday, 20 August 2012 0830h – 0900h Welcome and Logistics 0900h – 0945h Introduction – Hawaiian Volcano Observatory: Its First 100 Years of Advancing Volcanism 0945h – 1215h Magma Origin and Ascent I 1030h – 1045h Coffee Break 1215h – 1330h Lunch on Your Own 1330h – 1430h Magma Origin and Ascent II 1430h – 1445h Coffee Break 1445h – 1600h Magma Origin and Ascent Breakout Sessions I, II, III, IV, and V 1600h – 1645h Magma Origin and Ascent III 1645h – 1900h Poster Session Tuesday, 21 August 2012 0900h – 1215h Magma Storage and Island Evolution I 1215h – 1330h Lunch on Your Own 1330h – 1445h Magma Storage and Island Evolution II 1445h – 1600h Magma Storage and Island Evolution Breakout Sessions I, II, III, IV, and V 1600h – 1645h Magma Storage
    [Show full text]
  • The Science Behind Volcanoes
    The Science Behind Volcanoes A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "Plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so- called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth. Erupting volcanoes can pose many hazards, not only in the immediate vicinity of the eruption. Volcanic ash can be a threat to aircraft, in particular those with jet engines where ash particles can be melted by the high operating temperature. Large eruptions can affect temperature as ash and droplets of sulfuric acid obscure the sun and cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere.
    [Show full text]
  • The Hyaloclastite Ridge Formed in the Subglacial 1996 Eruption in Gjfilp, Vatnaj6kull, Iceland: Present Day Shape and Future Preservation
    The hyaloclastite ridge formed in the subglacial 1996 eruption in Gjfilp, Vatnaj6kull, Iceland: present day shape and future preservation M. T. GUDMUNDSSON, F. PALSSON, H. BJORNSSON & ~. HOGNADOTTIR Science Institute, University of Iceland, Hofsvallag6tu 53, 107 Reykjavik, Iceland (e-mail: [email protected]) Abstract: In the Gjfilp eruption in 1996, a subglacial hyaloclastite ridge was formed over a volcanic fissure beneath the Vatnaj6kull ice cap in Iceland. The initial ice thickness along the 6 km-long fissure varied from 550 m to 750 m greatest in the northern part but least in the central part where a subaerial crater was active during the eruption. The shape of the subglacial ridge has been mapped, using direct observations of the top of the edifice in 1997, radio echo soundings and gravity surveying. The subglacial edifice is remarkably varied in shape and height. The southern part is low and narrow whereas the central part is the highest, rising 450 m above the pre-eruption bedrock. In the northern part the ridge is only 150-200m high but up to 2kin wide, suggesting that lateral spreading of the erupted material occurred during the latter stages of the eruption. The total volume of erupted material in Gj~tlp was about 0.8 km 3, mainly volcanic glass. The edifice has a volume of about 0.7 km 3 and a volume of 0.07 km 3 was transported with the meltwater from Gj~lp and accumulated in the Grimsv6tn caldera, where the subglacial lake acted as a trap for the sediments. This meltwater-transported material was removed from the southern part of the edifice during the eruption.
    [Show full text]