1 Volcanic Hazards
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Source to Surface Model of Monogenetic Volcanism: a Critical Review
Downloaded from http://sp.lyellcollection.org/ by guest on September 28, 2021 Source to surface model of monogenetic volcanism: a critical review I. E. M. SMITH1 &K.NE´ METH2* 1School of Environment, University of Auckland, Auckland, New Zealand 2Volcanic Risk Solutions, Massey University, Palmerston North 4442, New Zealand *Correspondence: [email protected] Abstract: Small-scale volcanic systems are the most widespread type of volcanism on Earth and occur in all of the main tectonic settings. Most commonly, these systems erupt basaltic magmas within a wide compositional range from strongly silica undersaturated to saturated and oversatu- rated; less commonly, the spectrum includes more siliceous compositions. Small-scale volcanic systems are commonly monogenetic in the sense that they are represented at the Earth’s surface by fields of small volcanoes, each the product of a temporally restricted eruption of a composition- ally distinct batch of magma, and this is in contrast to polygenetic systems characterized by rela- tively large edifices built by multiple eruptions over longer periods of time involving magmas with diverse origins. Eruption styles of small-scale volcanoes range from pyroclastic to effusive, and are strongly controlled by the relative influence of the characteristics of the magmatic system and the surface environment. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Small-scale basaltic magmatic systems characteris- hazards associated with eruptions, and this is tically occur at the Earth’s surface as fields of small particularly true where volcanic fields are in close monogenetic volcanoes. These volcanoes are the proximity to population centres. -
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. -
Pyroclastic Flow Hazards
Pyroclastic Flow Hazards Lecture Objectives -definition and characteristics -generation of pyroclastic flows -impacts and hazards What are pyroclastic flows? Pyroclastic flows are high- density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds. Generation Mechanisms: -explosive eruption of molten or solid rock fragments, or both. -non-explosive eruption of lava when parts of dome or a thick lava flow collapses down a steep slope. Most pyroclastic flows consist of two parts: a basal flow of coarse fragments that moves along the ground, and a turbulent cloud of ash that rises above the basal flow. Ash may fall from this cloud over a wide area downwind from the pyroclastic flow. Mt. St. Helens Effects of pyroclastic flows A pyroclastic flow will destroy nearly everything in its path. With rock fragments ranging in size from ash to boulders traveling across the ground at speeds typically greater than 80 km per hour, pyroclastic flows knock down, shatter, bury or carry away nearly all objects and structures in their way. The extreme temperatures of rocks and gas inside pyroclastic flows, generally between 200°C and 700°C, can cause combustible material to burn, especially petroleum products, wood, vegetation, and houses. Pyroclastic flows vary considerably in size and speed, but even relatively small flows that move <5 km from a volcano can destroy buildings, forests, and farmland. On the margins of pyroclastic flows, death and serious injury to people and animals may result from burns and inhalation of hot ash and gases. Pyroclastic flows generally follow valleys or other low-lying areas and, depending on the volume of rock debris carried by the flow, they can deposit layers of loose rock fragments to depths ranging from less than one meter to more than 200 m. -
Review of Local and Global Impacts of Volcanic Eruptions and Disaster Management Practices: the Indonesian Example
geosciences Review Review of Local and Global Impacts of Volcanic Eruptions and Disaster Management Practices: The Indonesian Example Mukhamad N. Malawani 1,2, Franck Lavigne 1,3,* , Christopher Gomez 2,4 , Bachtiar W. Mutaqin 2 and Danang S. Hadmoko 2 1 Laboratoire de Géographie Physique, Université Paris 1 Panthéon-Sorbonne, UMR 8591, 92195 Meudon, France; [email protected] 2 Disaster and Risk Management Research Group, Faculty of Geography, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia; [email protected] (C.G.); [email protected] (B.W.M.); [email protected] (D.S.H.) 3 Institut Universitaire de France, 75005 Paris, France 4 Laboratory of Sediment Hazards and Disaster Risk, Kobe University, Kobe City 658-0022, Japan * Correspondence: [email protected] Abstract: This paper discusses the relations between the impacts of volcanic eruptions at multiple- scales and the related-issues of disaster-risk reduction (DRR). The review is structured around local and global impacts of volcanic eruptions, which have not been widely discussed in the literature, in terms of DRR issues. We classify the impacts at local scale on four different geographical features: impacts on the drainage system, on the structural morphology, on the water bodies, and the impact Citation: Malawani, M.N.; on societies and the environment. It has been demonstrated that information on local impacts can Lavigne, F.; Gomez, C.; be integrated into four phases of the DRR, i.e., monitoring, mapping, emergency, and recovery. In Mutaqin, B.W.; Hadmoko, D.S. contrast, information on the global impacts (e.g., global disruption on climate and air traffic) only fits Review of Local and Global Impacts the first DRR phase. -
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. -
Geological Mapping, Structural Setting and Petrographic Description of the Archean Volcanic Rocks of Mnanka Area, North Mara
PROCEEDINGS, 43rd Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 12-14, 2018 SGP-TR-213 Geological Mapping, Structural Setting and Petrographic Description of the Archean Volcanic Rocks of Mnanka Area, North Mara Ezra Kavana Acacia Mining PLc, North Mara Gold Mine, Department of Geology, P. O. Box 75864, Dar es Salaam, Tanzania Email: [email protected] Keywords: Musoma Mara Greenstone Belt, Mnanka volcanics, Archaean rocks and lithology ABSTRACT The Mnanka area is situated within the Musoma Mara Greenstone Belt, the area is near to Nyabigena, Gokona and Nyabirama gold mines. Mnanka area comprises of the sequence of predominant rhyolitic volcanic rocks, chert and metasediments. Gold mineralizations in Mnanka area is structure controlled and occur mainly as hydrothermal disseminated intrusion related deposits. Hence the predominant observed structures are joints and flow banding. Measurements from flow banding plotted on stereonets using win-TENSOR software has provided an estimate for the general strike of the area lying 070° to 100° dipping at an average range angle of 70° to 85° while data from joints plotted on stereonets suggest multiple deformation events one of which conforms to the East Africa Rift System (striking WSW-ENE, NNE-SSW and N-S). 1. INTRODUCTION This paper focuses on performing a systematic geological mapping and description of structures and rocks of the Mnanka area. The Mnanka area is located in the Mara region, Tarime district within the Musoma Mara Greenstone Belt. The gold at Mnanka is host ed by volcanic rocks that belong to the Musoma Mara Greenstone Belt (Figure 1). The Mnanka volcanics are found within the Kemambo group that comprises of the sequence of predominant rhyolitic volcanic rocks, chert and metasediments south of the Nyarwana fault. -
Explosive Eruptions
Explosive Eruptions -What are considered explosive eruptions? Fire Fountains, Splatter, Eruption Columns, Pyroclastic Flows. Tephra – Any fragment of volcanic rock emitted during an eruption. Ash/Dust (Small) – Small particles of volcanic glass. Lapilli/Cinders (Medium) – Medium sized rocks formed from solidified lava. – Basaltic Cinders (Reticulite(rare) + Scoria) – Volcanic Glass that solidified around gas bubbles. – Accretionary Lapilli – Balls of ash – Intermediate/Felsic Cinders (Pumice) – Low density solidified ‘froth’, floats on water. Blocks (large) – Pre-existing rock blown apart by eruption. Bombs (large) – Solidified in air, before hitting ground Fire Fountaining – Gas-rich lava splatters, and then flows down slope. – Produces Cinder Cones + Splatter Cones – Cinder Cone – Often composed of scoria, and horseshoe shaped. – Splatter Cone – Lava less gassy, shape reflects that formed by splatter. Hydrovolcanic – Erupting underwater (Ocean or Ground) near the surface, causes violent eruption. Marr – Depression caused by steam eruption with little magma material. Tuff Ring – Type of Marr with tephra around depression. Intermediate Magmas/Lavas Stratovolcanoes/Composite Cone – 1-3 eruption types (A single eruption may include any or all 3) 1. Eruption Column – Ash cloud rises into the atmosphere. 2. Pyroclastic Flows Direct Blast + Landsides Ash Cloud – Once it reaches neutral buoyancy level, characteristic ‘umbrella cap’ forms, & debris fall. Larger ash is deposited closer to the volcano, fine particles are carried further. Pyroclastic Flow – Mixture of hot gas and ash to dense to rise (moves very quickly). – Dense flows restricted to valley bottoms, less dense flows may rise over ridges. Steam Eruptions – Small (relative) steam eruptions may occur up to a year before major eruption event. . -
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.