GEOS 432-4; Volcanic processes and landforms
Plate Tectonics and Volcanism
Mantle hot spots Oceanic Basaltic Continental Rhyolitic, andesitic, or basaltic
Plate tectonics and Volcanism
Plate margins Divergent-basaltic
Subduction of oceanic plate-andesite
1 Large scale landforms
Submarine volcanoes
Large scale landforms
Basalt plateaus
Volcanic Products
Gas Lava Tephra
2 Gas
Vents Hot springs, geysers, fumaroles, solfataras
Hot springs Solfatara, Iceland
Geyser, ―Strokkur‖ at Geysir, Iceland
3 1 2
3 4
Mud volcano
http://ngm.nationalgeographic.com/ngm/20 08-01/volcano-culture/drowning-in- mud.html
4 Lake Nyos case history http://perso.wanadoo.fr/mhalb/nyos/index.htm
Lava
Composition Silica content: 35% (basalt) – 75% (rhyolite, obsidian) Viscosity Related to composition-higher silica—more viscous Temp and volatile content also important Volatiles decrease viscosity but degas at surface Basalt 1100-1200 degrees C
Lava flows
Vesicles AA Aaflow, lava Iceland
Pahoehoe lava Aa lava flow
5 Rhylolite/obsidian flow
Obsidian
Columnar jointing
6 Pillow lavas
Tephra
Ash—sand size & smaller Lapilli—gravel Blocks (Cold) Bombs (warm)
Pumice, 1875 eruption of Askja, Iceland 1875 Snow exposed
7 Pyroclastic eruptions
Heimaey, Iceland, 1973
2010 Eruption: Eyjafyallajökull
http://www.youtube.com/watch?v=f1ztg0wUqKY
Pyroclastic flow or surge
High temperature, very fast, very destructive
8 Mt. Pelee, 1902
Town of St. Pierre, Carribean Island of Martinique 30,000 killed
Mt. St. Helens, 1980
Lateral Blast
Debris flows, Mt. St. Helens
9 Mt St. Helens
Lahars Orting, Washington
Mt. Rainier
Mt. Shasta
10 Armero, Nevado del Ruiz, 1985
23,000 people killed
Volcanic landforms
ShieldShield volcano volcano Shield volcano L Lava flow Exogenous dome a v
a Scoria cone ScoriaScoria cone cone Scoria Scoria cone cone
Tuff ring
Endogenous dome Ruptured ED Composite (strato) volcano
Explosion caldera Maars with tephra Maar with rampart
Collapse caldera Gas maar Explosion crater
11 Lava flows—fissure or central vent
Young lava flow, Iceland
Fissures, Iceland
Iceland
Lava Cascade, Iceland Fissure, Craters of the Moon
12 Basalt flow Craters of the Moon Miocene basalt flows from fissures- Columbia River Plateau
Exogenous domes
Spatter cone-Iceland Shield Volcano-Iceland
Mauna Loa, as seen from Kilauea Mauna Loa from Kilauea
13 Pyroclastic cones, rings
Tuff ring, northern Iceland
Scoria cone
Tuff cone
14 Tuff Ring, Iceland
Lake Myvatn, Iceland
15 Endogenous domes
Mt. St. Helens
Composite (strato) volcanoes
16 Mt. Fuji
Craters, calderas
Maar, New Mexico Crater Lake
17 Halemaumau pit crater
Summit caldera, Askja Volcano, Iceland
Santorini, Greece
18 Miscellaneous
IcelandicIcelandic Table Table Mountain Mountain -Tuya
Tuya, Iceland
Miscellaneous con’t
Lava tube
Tumuli
Volcanic neck
Tree mold
19