Post on 06-Nov-2021
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GEOS 432-4; Volcanic processes and landforms
Plate Tectonics and VolcanismPlate Tectonics and Volcanism
Mantle hot spotsMantle hot spots
OceanicOceanic
BasalticBasaltic
ContinentalContinental
RhyoliticRhyolitic, andesitic, or , andesitic, or
basalticbasaltic
Plate tectonics and VolcanismPlate tectonics and Volcanism
Plate marginsPlate margins
DivergentDivergent--basalticbasaltic
Subduction of oceanic Subduction of oceanic
plateplate--andesiteandesite
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Large scale landformsLarge scale landforms
Submarine volcanoes
Large scale landformsLarge scale landforms
Basalt plateaus
Volcanic ProductsVolcanic Products
GasGas
LavaLava
TephraTephra
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GasGas
VentsVents
Hot springs, geysers, fumaroles, solfatarasHot springs, geysers, fumaroles, solfataras
Solfatara, Iceland Hot springs
Geyser, ―Strokkur‖ at
Geysir, Iceland
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1 2
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Mud volcanoMud volcano
http://ngm.nationalgeographic.com/ngm/20http://ngm.nationalgeographic.com/ngm/20
0808--01/volcano01/volcano--culture/drowningculture/drowning--inin--
mud.htmlmud.html
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Lake Nyos case historyLake Nyos case history http://perso.wanadoo.fr/mhalb/nyos/index.htmhttp://perso.wanadoo.fr/mhalb/nyos/index.htm
LavaLava
CompositionComposition
Silica content: 35% (basalt) Silica content: 35% (basalt) –– 75% (rhyolite, 75% (rhyolite,
obsidian)obsidian)
ViscosityViscosity
Related to compositionRelated to composition--higher silicahigher silica——more more
viscousviscous
Temp and volatile content also importantTemp and volatile content also important
Volatiles decrease viscosity but degas at surfaceVolatiles decrease viscosity but degas at surface
Basalt 1100Basalt 1100--1200 degrees C1200 degrees C
Lava flowsLava flows
Vesicles Aa lava
Pahoehoe lava Aa lava flow
AA flow, Iceland
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Rhylolite/obsidian flow
Obsidian
Columnar jointingColumnar jointing
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Pillow lavasPillow lavas
TephraTephra
AshAsh——sand size & sand size &
smallersmaller
LapilliLapilli——gravelgravel
Blocks (Cold) Bombs Blocks (Cold) Bombs
(warm)(warm)
Pumice, 1875 eruption of Askja, IcelandPumice, 1875 eruption of Askja, Iceland
1875 Snow exposed1875 Snow exposed
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Pyroclastic eruptionsPyroclastic eruptions
Heimaey, Iceland, 1973
2010 Eruption: 2010 Eruption: EyjafyallajökullEyjafyallajökull
http://www.youtube.com/watch?v=f1ztg0wUqKY
Pyroclastic flow or surgePyroclastic flow or surge
High temperature, very fast, very destructive
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Mt. Pelee, 1902Mt. Pelee, 1902
Town of St. Pierre, Carribean Island of Martinique 30,000 killed
Mt. St. Helens, 1980Mt. St. Helens, 1980
Lateral Blast
Debris flows, Mt. St. HelensDebris flows, Mt. St. Helens
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Mt St. Helens
LaharsLahars
Mt. Rainier
Orting, Washington
Mt. ShastaMt. Shasta
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ArmeroArmero, , NevadoNevado del Ruiz, 1985del Ruiz, 1985
23,000 people killed
Volcanic landformsVolcanic landforms
L
a
v
a
Lava flow Exogenous dome Shield volcano Shield volcano
Scoria cone
Scoria cone
Shield volcano
Scoria cone Scoria cone Scoria cone
Tuff ring
Composite (strato) volcano Endogenous dome Ruptured ED
Maars with tephra Maar with rampart
Explosion caldera
Collapse caldera
Gas maar Explosion crater
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Lava flowsLava flows——fissure or central ventfissure or central vent
Fissures, Iceland
Young lava flow, Iceland
Iceland
Lava Cascade, Iceland Fissure, Craters of the Moon
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Basalt flow Craters of the Moon Miocene basalt flows from fissures-
Columbia River Plateau
Exogenous domesExogenous domes
Spatter cone-Iceland Shield Volcano-Iceland
Mauna Loa from Kilauea
Mauna Loa, as seen from Kilauea
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Pyroclastic cones, ringsPyroclastic cones, rings
Tuff ring, northern Iceland
Scoria coneScoria cone
Tuff coneTuff cone
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Tuff Ring, Iceland
Lake Myvatn, IcelandLake Myvatn, Iceland
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Endogenous domesEndogenous domes
Mt. St. Helens
Composite (strato) volcanoesComposite (strato) volcanoes
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Mt. Fuji
Craters, calderasCraters, calderas
Maar, New Mexico Crater Lake
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Halemaumau pit craterHalemaumau pit crater
Summit caldera, Askja Volcano, IcelandSummit caldera, Askja Volcano, Iceland
Santorini, GreeceSantorini, Greece
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MiscellaneousMiscellaneous
Icelandic Table Mountain Icelandic Table Mountain-Tuya
Tuya, Iceland
Miscellaneous Miscellaneous con’tcon’t
Lava tube
Tumuli
Tree mold
Volcanic neck