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Volcanoes Volcanoes

Overview • • • Magma Sources and Types Kinds and Locations of Volcanic Activity Overview • • • Magma Sources and Types Kinds and Locations of Volcanic Activity Hazards Related to Volcanoes Issues in Predicting Volcanic Eruptions Present and Future Volcanic Hazards in the United States

Magma Source • Areas Where Magma Forms (need heat!) – Upper mantle: asthenosphere – Magma Source • Areas Where Magma Forms (need heat!) – Upper mantle: asthenosphere – depths of ~ 50 to 250 km – High temps (800 -1100 C), medium pressure – Rocks melt, or partially melt – Divergent plate boundaries – Above subduction zones – Hot spots

Plate tectonics: Asthenosphere is where melting occurs Source: http: //www. geol. umd. edu/~jmerck/gal 04/GEOL Plate tectonics: Asthenosphere is where melting occurs Source: http: //www. geol. umd. edu/~jmerck/gal 04/GEOL 388/lectures/02. html

Wahalua Visitors’ Center Aflame in Hawaii Source: Photograph by J. D. Griggs, USGS Photo Wahalua Visitors’ Center Aflame in Hawaii Source: Photograph by J. D. Griggs, USGS Photo Library, Denver, CO.

Ruins of the Visitors’ Center After Lava Cooled Source: Photograph by J. D. Griggs, Ruins of the Visitors’ Center After Lava Cooled Source: Photograph by J. D. Griggs, USGS Photo Library, Denver, CO.

Magma Types • Composition: – Magmas: >Fe, Mg (mafic) vs >Si. O 2 (felsic) Magma Types • Composition: – Magmas: >Fe, Mg (mafic) vs >Si. O 2 (felsic) • Dependent on tectonic setting (1) Ocean spreading ridges and hot spots: Mafic rocks (basalt) (2) Continental rifts: felsic (rhyolite, andesite) (3) Subduction zones: mafic + felsic

Mafic: Basalt Ultramafic: Peridotite Source: http: //www. tmm. utexas. edu/npl/mineralogy/Blowups/Olivine_in_peridotite_xenolith. htm Mafic: Basalt Ultramafic: Peridotite Source: http: //www. tmm. utexas. edu/npl/mineralogy/Blowups/Olivine_in_peridotite_xenolith. htm

Felsic-mafic: andesite Source: http: //www. otago. ac. nz/geology/features/rocks-minerals/rocks. html Felsic-mafic: andesite Source: http: //www. otago. ac. nz/geology/features/rocks-minerals/rocks. html

Felsic: Rhyolite Source: http: //resourcescommittee. house. gov/subcommittees/emr/usgsweb/photogallery/ Felsic: Rhyolite Source: http: //resourcescommittee. house. gov/subcommittees/emr/usgsweb/photogallery/

Magma properties • Volcanic Gases: CO 2, SO 2 • Pressure builds up as Magma properties • Volcanic Gases: CO 2, SO 2 • Pressure builds up as magmas rises to surface – Felsic (more Si. O 2): viscous + thick = explosive – Mafic (less Si. O 2): fluid, gases escape *What kind of volcano is safest to live by?

Lava Flows on Kilauea in Hawaii Source: Photograph courtesy of USGS Photo Library, Denver, Lava Flows on Kilauea in Hawaii Source: Photograph courtesy of USGS Photo Library, Denver, CO.

Hawaiian Lavas: mafic basalts Source: Courtesy of Carla W. Montgomery. Hawaiian Lavas: mafic basalts Source: Courtesy of Carla W. Montgomery.

Volcanic Breccia (felsic) Source: Courtesy of Carla W. Montgomery. Volcanic Breccia (felsic) Source: Courtesy of Carla W. Montgomery.

Kinds and Locations of Volcanic Activity • Individual Volcanoes–Locations • Seafloor Spreading Ridges, Fissure Kinds and Locations of Volcanic Activity • Individual Volcanoes–Locations • Seafloor Spreading Ridges, Fissure Eruptions • Shield Volcanoes • Volcanic Domes • Cinder Cones • Composite Volcanoes

Volcanoes of the World Source: After R. Decker and B. Decker, Volcanoes, 1981, W. Volcanoes of the World Source: After R. Decker and B. Decker, Volcanoes, 1981, W. H. Freeman and Company, New York, NY.

“Hot Spots” Around the World Source: Modified after map in online text This Dynamic “Hot Spots” Around the World Source: Modified after map in online text This Dynamic Earth, U. S. Geological Survey.

Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii – Mafic lavas, low, Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii – Mafic lavas, low, flat, ‘shields’ • Volcanic Domes • Cinder Cones • Composite Volcanoes

Low-Angle View of Mauna Loa Source: Photograph courtesy of USGS Photo Library, Denver, CO. Low-Angle View of Mauna Loa Source: Photograph courtesy of USGS Photo Library, Denver, CO.

Satellite View of Hawaii Source: Photograph courtesy of USGS Photo Library, Denver, CO. Satellite View of Hawaii Source: Photograph courtesy of USGS Photo Library, Denver, CO.

Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii – Mafic lavas, low, Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii – Mafic lavas, low, flat, ‘shields’ • Volcanic Domes: Mt. St. Helens – Rhyolite, andesitic lavas. – Thick, viscous lavas (domes) • Cinder Cones • Composite Volcanoes

Dome Formation, Mount St. Helens Source: Photograph courtesy of USGS Photo Library, Denver, CO. Dome Formation, Mount St. Helens Source: Photograph courtesy of USGS Photo Library, Denver, CO.

Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii • Volcanic Domes: Mt. Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii • Volcanic Domes: Mt. St. Helens – Rhyolite, andesitic lavas. – Thick, viscous lavas (domes) • Cinder Cones: common – Release of gas pressure (pop bottle) – Produces pyroclastics • Composite Volcanoes

Paricutín Volcano Erupting Source: Photograph courtesy of USGS Photo Library, Denver, CO. Paricutín Volcano Erupting Source: Photograph courtesy of USGS Photo Library, Denver, CO.

Paricutín Showing Form of Cinder Cones Source: Photograph by K. Segerstrom, courtesy of USGS Paricutín Showing Form of Cinder Cones Source: Photograph by K. Segerstrom, courtesy of USGS Photo Library, Denver, CO.

Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii • Volcanic Domes: inside Kinds and Locations of Volcanic Activity • Shield Volcanoes: Hawaii • Volcanic Domes: inside Mt. St. Helens • Cinder Cones: common – Release of gas pressure (pop bottle) – Produces pyroclastics • Composite Volcanoes (stratovolcanoes) • Calderas

Source: http: //www. enchantedlearning. com/subjects/volcano/gifs/volcanodiagram. GIF Source: http: //www. enchantedlearning. com/subjects/volcano/gifs/volcanodiagram. GIF

Composite Volcano in the Aleutian Islands Source: Photograph by R. E. Wilcox, USGS Photo Composite Volcano in the Aleutian Islands Source: Photograph by R. E. Wilcox, USGS Photo Library, Denver, CO.

Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of ash and water) Pyroclastic Flows–Nuées Ardentes Toxic Gases Steam Explosions Secondary Effects: Climate and Atmospheric Chemistry

Formation of “Lava Trees” Near Kilauea Source: Photograph by J. D. Griggs, USGS Photo Formation of “Lava Trees” Near Kilauea Source: Photograph by J. D. Griggs, USGS Photo Library, Denver, CO.

Map Showing Lava Filling Harbor in Iceland Source: Data from R. Decker and B. Map Showing Lava Filling Harbor in Iceland Source: Data from R. Decker and B. Decker, Volcanoes, Copyright © 1981 by W. H. Freeman and Company.

Lava-Flow Control Efforts on Heimaey Harbor Source: Photograph courtesy of USGS Photo Library, Denver, Lava-Flow Control Efforts on Heimaey Harbor Source: Photograph courtesy of USGS Photo Library, Denver, CO.

Pyroclastics Ejected During Eruptions Source: Data from U. S. Geological Survey. Pyroclastics Ejected During Eruptions Source: Data from U. S. Geological Survey.

Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of ash and water) Pyroclastic Flows–Nuées Ardentes Toxic Gases Steam Explosions Secondary Effects: Climate and Atmospheric Chemistry

Aftermath. Mt. St. Helens Eruption, 1980 Source: Photograph by M. M. Brugman, USGS Photo Aftermath. Mt. St. Helens Eruption, 1980 Source: Photograph by M. M. Brugman, USGS Photo Library, Denver, CO.

Ash and Rains Cause Structure Collapse Source: Photograph by R. P. Hoblitt, courtesy U. Ash and Rains Cause Structure Collapse Source: Photograph by R. P. Hoblitt, courtesy U. S. Geological Survey.

Mudflow and Flood Damage from Mt. St. Helens Source: Photograph by C. D. Miller, Mudflow and Flood Damage from Mt. St. Helens Source: Photograph by C. D. Miller, USGS Photo Library, Denver, CO.

Abacan River Mudflows, Philippines Source: Photograph by T. J. Casadervall, U. S. Geological Survey. Abacan River Mudflows, Philippines Source: Photograph by T. J. Casadervall, U. S. Geological Survey.

Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of ash and water) Pyroclastic Flows–Nuées Ardentes – ‘Glowing cloud’ • Toxic Gases • Steam Explosions • Secondary Effects: Climate and Atmospheric Chemistry

Pyroclastic Flow from Mount St. Helens Source: Photograph by P. W. Lipman, USGS Photo Pyroclastic Flow from Mount St. Helens Source: Photograph by P. W. Lipman, USGS Photo Library, Denver, CO.

Nuée Ardente from Mont Pelée, 1902: *25, 000 – 40, 000 people died Source: Nuée Ardente from Mont Pelée, 1902: *25, 000 – 40, 000 people died Source: Photograph by Underwood and Underwood, courtesy Library of Congress.

Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of ash and water) Pyroclastic Flows–Nuées Ardentes Toxic Gases Steam Explosions Secondary Effects: Climate and Atmospheric Chemistry

Toxic gases: CO 2? Cameroon, 1986 Source: http: //wps. prenhall. com/wps/media/objects/476/488316/ch 13. html Toxic gases: CO 2? Cameroon, 1986 Source: http: //wps. prenhall. com/wps/media/objects/476/488316/ch 13. html

Carbon Dioxide Cloud Over Lake Nyos, Cameroon Source: Photograph by M. L. Tuttle, USGS Carbon Dioxide Cloud Over Lake Nyos, Cameroon Source: Photograph by M. L. Tuttle, USGS Photo Library, Denver, CO.

Animal Carcasses From Deadly Cloud: 1700 people died Source: Photograph by M. L. Tuttle, Animal Carcasses From Deadly Cloud: 1700 people died Source: Photograph by M. L. Tuttle, USGS Photo Library, Denver, CO.

Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of Hazards Related to Volcanoes • • Lava Pyroclastics (rocks and lava) Lahars (mudflow of ash and water) Pyroclastic Flows–Nuées Ardentes Toxic Gases Steam Explosions Secondary Effects: Climate and Atmospheric Chemistry

Mt. Pinatubo Eruption, 1991 Source: Photograph by K. Jackson, U. S. Air Force. Mt. Pinatubo Eruption, 1991 Source: Photograph by K. Jackson, U. S. Air Force.

Source: http: //eos. higp. hawaii. edu// Source: http: //eos. higp. hawaii. edu//

Source: http: //volcanoes. usgs. gov/Imgs/Jpg/Pinatubo/16112441 -008_large. jpg Source: http: //volcanoes. usgs. gov/Imgs/Jpg/Pinatubo/16112441 -008_large. jpg

The atmosphere: different levels Source: http: //pubs. usgs. gov/publications/text/tectonics. html#anchor 10693467 The atmosphere: different levels Source: http: //pubs. usgs. gov/publications/text/tectonics. html#anchor 10693467

Stratospheric Aerosol, 1991: April 15 - May 25 Source: http: //eos. higp. hawaii. edu// Stratospheric Aerosol, 1991: April 15 - May 25 Source: http: //eos. higp. hawaii. edu//

Stratospheric Aerosol, 1991: June 14 – July 26 Source: http: //eos. higp. hawaii. edu// Stratospheric Aerosol, 1991: June 14 – July 26 Source: http: //eos. higp. hawaii. edu//

Stratospheric Aerosol, 1993: Feb. 13 – March 26 Source: http: //eos. higp. hawaii. edu// Stratospheric Aerosol, 1993: Feb. 13 – March 26 Source: http: //eos. higp. hawaii. edu//