Chapter 5 Key Concepts
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Chapter 2 Alaska’S Igneous Rocks
Chapter 2 Alaska’s Igneous Rocks Resources • Alaska Department of Natural Resources, 2010, Division of Geological and Geophysical Surveys, Alaska Geologic Materials Center website, accessed May 27, 2010, at http://www.dggs.dnr.state.ak.us/?link=gmc_overview&menu_link=gmc. • Alaska Resource Education: Alaska Resource Education website, accessed February 22, 2011, at http://www.akresource.org/. • Barton, K.E., Howell, D.G., and Vigil, J.F., 2003, The North America tapestry of time and terrain: U.S. Geological Survey Geologic Investigations Series I-2781, 1 sheet. (Also available at http://pubs.usgs.gov/imap/i2781/.) • Danaher, Hugh, 2006, Mineral identification project website, accessed May 27, 2010, at http://www.fremontica.com/minerals/. • Digital Library for Earth System Education, [n.d.], Find a resource—Bowens reaction series: Digital Library for Earth System Education website, accessed June 10, 2010, at http://www.dlese.org/library/query.do?q=Bowens%20reaction%20series&s=0. • Edwards, L.E., and Pojeta, J., Jr., 1997, Fossils, rocks, and time: U.S. Geological Survey website. (Available at http://pubs.usgs.gov/gip/fossils/contents.html.) • Garden Buildings Direct, 2010, Rocks and minerals: Garden Buildings Direct website, accessed June 4, 2010, at http://www.gardenbuildingsdirect.co.uk/Article/rocks-and- minerals. • Illinois State Museum, 2003, Geology online–GeoGallery: Illinois State Museum Society database, accessed May 27, 2010 at http://geologyonline.museum.state.il.us/geogallery/. • Knecht, Elizebeth, designer, Pearson, R.W., and Hermans, Majorie, eds., 1998, Alaska in maps—A thematic atlas: Alaska Geographic Society, 100 p. Lillie, R.J., 2005, Parks and plates—The geology of our National parks, monuments, and seashores: New York, W.W. -
Depth and Degree of Melting of Komatiites
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 97, NO. B4, PAGES 4521-4540, APRIL 10, 1992 Depth and Degree of Melting of Komatiites CLAUDE HERZBERG Departmentof GeologicalSciences, Rutgers University,New Brunswick,New Jersey Mineral PhysicsInstitute, State Universityof New York, StonyBrook, New York High pressuremelting experimentsßhove ." v .......... new constraintsto be placedon the depthand degreeof partial melting of komatiites. Komatiitesfrom GorgonaIsland were formed by relatively low degreesof pseudoinvariantmelting(< 30 %)involving L + O1 + Opx + Cpx + Gt on the solidusat 40 kbar, about 130 km depth. Munro-typekomatiites were separatedfrom a harzburgiteresidue (L + O1 + Opx) at pressuresthat are poorly constrained,but were probablyaround 50 kbar, about 165 km depth;the degreeof partial melting was <40%. Komatiites from the BarbertonMountain Land were formed by high degrees(-50 %) of pseudoinvariantmelting (L + O1 + Gt + Cpx) of fertile mantleperidotitc in the 80- to 100-kbarrange, about 260- to 330- km depth. Secularvariations in the geochemistryof komatiitescould have formed in response to a reductionin the temperatureand pressureof meltingwith time. The 3.5 Ga Barbertonkomatiites and the 2.7 Ga Munro-typekomatiites could have formedin plumesthat were hotterthan the present-daymantle by 500ø and 30(Y',respectively. When excesstemperatures are this size, melting is deeperand volcanismchanges from basalticto komatiitic. The komatiitesfrom Gorgona Island, which are Mesozoic in age, may be representativeof komatiitesthat are predictedto occur in oceanicplateaus of Cretaceousage throughoutthe Pacific [Storey et al., 1991]. 1. INTRODUCTION range of CaO and A1203contents in the 80- to 160-kbar range. A calibration has been made of the effect of pressure on Komatiites are high MgO volcanic rocks that can be CaO/(CaO + A1203)and MgO in komatiiticliquids formed on roughly explained by high degrees of melting of mantle the solidus, and an examinationhas been made of the effect of peridotitc,typically 50 to 100 % [e.g., Vi.ljoenand Vi.ljoen, FeO. -
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. -
Lecture 8: Volcanism
Lecture 8: Volcanism EAS 2200 Introduction to the Earth System Today’s Plan Introduction Melting in the Earth mid-ocean ridges subduction zones mantle plumes Crystallization of igneous rocks Volcanic eruptions Introduction Volcanic eruptions are among the most spectacular natural phenomena. Where does the magma come from? Why does most volcanism occur only in certain areas? What causes eruptions to sometimes be catastrophic and sometimes quiescent? Why is there such a variety of igneous rocks? Where does magma come from? Early ideas: Hot vapors produce melting Burning coals layers provide heat for melting Global layer of molten rock at depth Modern ideas: Decompression melting Flux melting Intrusions of magma into the crust (but this begs the question of the origin of the original magma). Deep burial of low melting point material (rare). Melting of Rock Complex (“multi-phase”) substances progressively melt over a range of temperatures. The lowest temperature at which melt exists (temperature at which melting begins) is known as the solidus. The highest temperature at which solid persists (temperature at which melting is complete) is known as the liquidus. The melting range for most rocks (diference in solidus and liquidus) is several hundred degrees C. In essentially all cases, melting in the Earth is believed to be partial (i.e., liquidus temperature Volcanoes are like Clouds Decompression Melting Solidus temperature of rock decreases with decreasing pressure. Temperature of rising mantle rock also decreases with pressure (adiabatic decompression). Adiabat is steeper than solidus, so that rising mantle rock eventually reaches solidus and Melting and Mantle Convection We can expect melting to occur within hot, rising mantle convection cells. -
Volcanism on Mars
Author's personal copy Chapter 41 Volcanism on Mars James R. Zimbelman Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC, USA William Brent Garry and Jacob Elvin Bleacher Sciences and Exploration Directorate, Code 600, NASA Goddard Space Flight Center, Greenbelt, MD, USA David A. Crown Planetary Science Institute, Tucson, AZ, USA Chapter Outline 1. Introduction 717 7. Volcanic Plains 724 2. Background 718 8. Medusae Fossae Formation 725 3. Large Central Volcanoes 720 9. Compositional Constraints 726 4. Paterae and Tholi 721 10. Volcanic History of Mars 727 5. Hellas Highland Volcanoes 722 11. Future Studies 728 6. Small Constructs 723 Further Reading 728 GLOSSARY shield volcano A broad volcanic construct consisting of a multitude of individual lava flows. Flank slopes are typically w5, or less AMAZONIAN The youngest geologic time period on Mars identi- than half as steep as the flanks on a typical composite volcano. fied through geologic mapping of superposition relations and the SNC meteorites A group of igneous meteorites that originated on areal density of impact craters. Mars, as indicated by a relatively young age for most of these caldera An irregular collapse feature formed over the evacuated meteorites, but most importantly because gases trapped within magma chamber within a volcano, which includes the potential glassy parts of the meteorite are identical to the atmosphere of for a significant role for explosive volcanism. Mars. The abbreviation is derived from the names of the three central volcano Edifice created by the emplacement of volcanic meteorites that define major subdivisions identified within the materials from a centralized source vent rather than from along a group: S, Shergotty; N, Nakhla; C, Chassigny. -
Volcanic Eruptions
Volcanic Eruptions •Distinguish between nonexplosive and explosive volcanic eruptions. • Identify the features of a volcano. • Explain how the composition of magma affects the type of volcanic eruption that will occur. • Describe four types of lava and four types of pyroclastic material. I. Volcanic Eruptions A. A volcano is a vent or fissure in the Earth’s surface through which molten rock and gases are expelled. B. Molten rock is called magma. C. Magma that flows onto the Earth’s surface is called lava. II. Nonexplosive Eruptions A. Nonexplosive eruptions are the most common type of volcanic eruptions. These eruptions produce relatively calm flows of lava in huge amounts. B. Vast areas of the Earth’s surface, including much of the sea floor and the Northwestern United States, are covered with lava form nonexplosive eruptions. Kilauea Volcano in Hawaii Island III. Explosive Eruptions A. While explosive eruptions are much rarer than non-explosive eruptions, the effects can be incredibly destructive. B. During an explosive eruption, clouds of hot debris, ash, and gas rapidly shoot out from a volcano. C. An explosive eruption can also blast millions of tons of lava and rock from a volcano, and can demolish and entire mountainside. Alaska's Mount Redoubt eruption in March 2009 IV. What Is Inside a Volcano? A. The interior of a volcano is made up of two main features. B. The magma chamber is the body of molten rock deep underground that feeds a volcano. C. The vent is an opening at the surface of the Earth through which volcanic material passes. -
Scale Deformation of Volcanic Centres in the Central Andes
letters to nature 14. Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides of 1–1.5 cm yr21 (Fig. 2). An area in southern Peru about 2.5 km and chalcogenides. Acta Crystallogr. A 32, 751–767 (1976). east of the volcano Hualca Hualca and 7 km north of the active 15. Hansen, M. (ed.) Constitution of Binary Alloys (McGraw-Hill, New York, 1958). 21 16. Emsley, J. (ed.) The Elements (Clarendon, Oxford, 1994). volcano Sabancaya is inflating with U LOS of about 2 cm yr . A third 21 17. Tanaka, H., Takahashi, I., Kimura, M. & Sobukawa, H. in Science and Technology in Catalysts 1994 (eds inflationary source (with ULOS ¼ 1cmyr ) is not associated with Izumi, Y., Arai, H. & Iwamoto, M.) 457–460 (Kodansya-Elsevier, Tokyo, 1994). a volcanic edifice. This third source is located 11.5 km south of 18. Tanaka, H., Tan, I., Uenishi, M., Kimura, M. & Dohmae, K. in Topics in Catalysts (eds Kruse, N., Frennet, A. & Bastin, J.-M.) Vols 16/17, 63–70 (Kluwer Academic, New York, 2001). Lastarria and 6.8 km north of Cordon del Azufre on the border between Chile and Argentina, and is hereafter called ‘Lazufre’. Supplementary Information accompanies the paper on Nature’s website Robledo caldera, in northwest Argentina, is subsiding with U (http://www.nature.com/nature). LOS of 2–2.5 cm yr21. Because the inferred sources are more than a few kilometres deep, any complexities in the source region are damped Acknowledgements such that the observed surface deformation pattern is smooth. -
Canadian Volcanoes, Based on Recent Seismic Activity; There Are Over 200 Geological Young Volcanic Centres
Volcanoes of Canada 1 V4 C.J. Hickson and M. Ulmi, Jan. 3, 2006 • Global Volcanism and Plate tectonics Where do volcanoes occur? Driving forces • Volcano chemistry and eruption types • Volcanic Hazards Pyroclastic flows and surges Lava flows Ash fall (tephra) Lahars/Debris Flows Debris Avalanches Volcanic Gases • Anatomy of an Eruption – Mt. St. Helens • Volcanoes of Canada Stikine volcanic belt Presentation Outline Anahim volcanic belt Wells Gray – Clearwater volcanic field 2 Garibaldi volcanic belt • USA volcanoes – Cascade Magmatic Arc V4 Volcanoes in Our Backyard Global Volcanism and Plate tectonics In Canada, British Columbia and Yukon are the host to a vast wealth of volcanic 3 landforms. V4 How many active volcanoes are there on Earth? • Erupting now about 20 • Each year 50-70 • Each decade about 160 • Historical eruptions about 550 Global Volcanism and Plate tectonics • Holocene eruptions (last 10,000 years) about 1500 Although none of Canada’s volcanoes are erupting now, they have been active as recently as a couple of 4 hundred years ago. V4 The Earth’s Beginning Global Volcanism and Plate tectonics 5 V4 The Earth’s Beginning These global forces have created, mountain Global Volcanism and Plate tectonics ranges, continents and oceans. 6 V4 continental crust ic ocean crust mantle Where do volcanoes occur? Global Volcanism and Plate tectonics 7 V4 Driving Forces: Moving Plates Global Volcanism and Plate tectonics 8 V4 Driving Forces: Subduction Global Volcanism and Plate tectonics 9 V4 Driving Forces: Hot Spots Global Volcanism and Plate tectonics 10 V4 Driving Forces: Rifting Global Volcanism and Plate tectonics Ocean plates moving apart create new crust. -
Processes Culminating in the 2015 Phreatic Explosion at Lascar Volcano, Chile, Evidenced by Multiparametric Data
Nat. Hazards Earth Syst. Sci., 20, 377–397, 2020 https://doi.org/10.5194/nhess-20-377-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Processes culminating in the 2015 phreatic explosion at Lascar volcano, Chile, evidenced by multiparametric data Ayleen Gaete1, Thomas R. Walter1, Stefan Bredemeyer1,2, Martin Zimmer1, Christian Kujawa1, Luis Franco Marin3, Juan San Martin4, and Claudia Bucarey Parra3 1GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany 2GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany 3Observatorio Volcanológico de Los Andes del Sur (OVDAS), Servicio Nacional de Geología y Minería (SERNAGEOMIN), Temuco, Chile 4Physics Science Department, Universidad de la Frontera, Casilla 54-D, Temuco, Chile Correspondence: Ayleen Gaete ([email protected]) Received: 13 June 2019 – Discussion started: 25 June 2019 Accepted: 5 December 2019 – Published: 4 February 2020 Abstract. Small steam-driven volcanic explosions are com- marole on the southern rim of the Lascar crater revealed a mon at volcanoes worldwide but are rarely documented or pronounced change in the trend of the relationship between monitored; therefore, these events still put residents and the CO2 mixing ratio and the gas outlet temperature; we tourists at risk every year. Steam-driven explosions also oc- speculate that this change was associated with the prior pre- cur frequently (once every 2–5 years on average) at Lascar cipitation event. An increased thermal anomaly inside the ac- volcano, Chile, where they are often spontaneous and lack tive crater as observed in Sentinel-2 images and drone over- any identifiable precursor activity. -
High-Silica Lava Morphology at Ocean Spreading Ridges: Machine-Learning Seafloor Classification at Alarcon Rise
Article High-Silica Lava Morphology at Ocean Spreading Ridges: Machine-Learning Seafloor Classification at Alarcon Rise Christina H. Maschmeyer 1,†, Scott M. White 1,*, Brian M. Dreyer 2 and David A. Clague 3 1 School of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC 29208, USA; [email protected] 2 Institute of Marine Sciences, University of California, Santa Cruz, CA 95064, USA; [email protected] 3 Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA; [email protected] † Now at: Fugro USA Marine, Inc. Geoconsulting Exploration, 6100 Hillcroft Ave, Houston, TX 77081, USA * Correspondence: [email protected] Received 31 March 2019; Accepted 28 May 2019; Published: 1 June 2019 Abstract: The oceanic crust consists mostly of basalt, but more evolved compositions may be far more common than previously thought. To aid in distinguishing rhyolite from basaltic lava and help guide sampling and understand spatial distribution, we constructed a classifier using neural networks and fuzzy inference to recognize rhyolite from its lava morphology in sonar data. The Alarcon Rise is ideal to study the relationship between lava flow morphology and composition, because it exhibits a full range of lava compositions in a well‐mapped ocean ridge segment. This study shows that the most dramatic geomorphic threshold in submarine lava separates rhyolitic lava from lower‐silica compositions. Extremely viscous rhyolite erupts as jagged lobes and lava branches in submarine environments. An automated classification of sonar data is a useful first‐order tool to differentiate submarine rhyolite flows from widespread basalts, yielding insights into eruption, emplacement, and architecture of the ocean crust. -
Nicaragua's Cerro Negro Stratovolcano
NICARAGUANICARAGUA’S’S CERROCERRO NEGRONEGRO STRASTRATOVTOVOLCANOOLCANO —— HOW DID IT BLOW ITS TOP??? 1) A stratovolcano or composite volcano 6) Large cloud of pyroclastic debris, is built of alternating layers of lava Match the explanations with the numbers on the volcano and find out. steam, and other vapors erupted and pyroclastic (ash or ejected de- from Cerro Negro. The larger, bris) deposits. These deposits accu- heavier fragments fall back on the mulate around the central vent in a cone while the smaller, lighter ash cone-shaped pile. Lava may flow from 6 fragments are carried great dis- fissures (fractures or cracks) radi- tances before they settle. ating from the central vent, whereas the multi-sized pyroclastics are B 7) A smaller cloud of darker material ejected from the main vent. 9 indicates that a localized eruption L has just occurred. 2) Steam and other vapors rising from 10 the large volcanic blocks erupted 8 from the main crater recently. Com- ) Cloud of vapors from the volcano is mostly steam and ash, but also con- pare with the older, cooler volcanic 8 tains chlorine, fluorine, sulfur, and blocks at the ends of the tracks or L 5 their acids. furrows that run down the slope of 5 the main cone. These tracks or fur- 5 9 rows were plowed by the rolling 7 9) Shadow cast by the ash and vapor blocks. Some house-size blocks now 5 cloud from the volcano (6) carried lie loosely at the bottom of the 5 by turbulent hot gasses and winds. slope. 4 When the volcanic ash settles, the 2 pyroclastic deposit that forms is 9 called an ash fall. -
Features of Lava Lake Filling and Draining and Their Implications for Eruption Dynamics
Bull Volcanol (2009) 71:767–780 DOI 10.1007/s00445-009-0263-0 RESEARCH ARTICLE Features of lava lake filling and draining and their implications for eruption dynamics W. K. Stovall & Bruce F. Houghton & Andrew J. L. Harris & Donald A. Swanson Received: 13 March 2008 /Accepted: 7 January 2009 /Published online: 13 February 2009 # Springer-Verlag 2009 Abstract Lava lakes experience filling, circulation, and roughly horizontal lava shelves on the lakeward edge of the often drainage depending upon the style of activity and vertical rinds; the shelves correlate with stable, staggered lake location of the vent. Features formed by these processes stands. Shelves either formed as broken relict slabs of lake have proved difficult to document due to dangerous crust that solidified in contact with the wall or by accumula- conditions during the eruption, inaccessibility, and destruction tion, accretion, and widening at the lake surface in a dynamic of features during lake drainage. Kīlauea Iki lava lake, lateral flow regime. Thin, upper lava shelves reflect an Kīlauea, Hawai‘i, preserves many such features, because lava initially dynamic environment, in which rapid lake lowering ponded in a pre-existing crater adjacent to the vent and was replaced by slower and more staggered drainage with the eventually filled to the level of, and interacted with, the vent formation of thicker, more laterally continuous shelves. At all and lava fountains. During repeated episodes, a cyclic pattern lava lakes experiencing stages of filling and draining these of lake filling to above vent level, followed by draining back processes may occur and result in the formation of similar sets to vent level, preserved features associated with both filling of features.