1EXTRUSIVE IGNEOUS ROCKSVolcanoes and Volcanic RocksWhat’s your favorite volcano?Famous Volcanoes•Basalts•Dotsero, CO•Kilauea•Mauna Loa•Haleakala•Hekla•Andesites•Fuji•St. Helens•Ranier•Shasta•Stromboli•Vesuvius•Popocatepetl•Orizaba•Pelée•Rhyolites•Yellowstone•Valles•Long Valley •Crater Lake•Pinatubo•Krakatao•Santorini•Campi Phlegri (Naples)Do you clean your volcanoes regularly?Where do volcanoes occur? Where do volcanoes occur?•Plate Boundaries (98%)–Divergent–Ocean-ocean convergent–Ocean-continent Convergent•Hot (wet) Spots2Where do volcanoes not occur?•Cratons•Passive continental margins•Oceanic abyssal plains•Continent – continent convergent boundariesMost Volcanoes are at Plate BoundariesIgneous Rock Names and Compositions• Intrusive Rock Name•Peridotite•Gabbro•Diorite•Granite• Composition Name•Ultramafic•Mafic•Intermediate•Silicic (felsic)• Volcanic Rock Name•(Komatiite)•Basalt•Andesite•RhyoliteMagma and Lava•Magma is the term for any molten silicate material, whether below the surface or on top.•Volcanic rocks are erupted on the surface.–Volcanic rocks are fine-grained (<1 mm)•Lava is the term for a magma on the surface.Most Volcanoes are at Plate BoundariesGeologic Settings3Basaltic Eruptions•Low Viscosity•High Temperature (1000 - 1200ºC)•Normally Quiescent Lava Flows–Aa - early, low temperature, blocky flow–Pahoehoe - later high temperature ropy flow–Pillow Lavas - underwater flow•Edifice–Shields–Cinder conesPahoehoe, Hawaii (Basalt)Aa, Hawaii (Basalt)Pillow Lava, Kauai (Basalt)Cinder Cone, Pu’uo’o,Hawaii(Basalt)Most Volcanoes are at Plate Boundaries4Cinder Cone + Caldera, (Basalt)Skjaldbreidur Shield, (Basalt)Caldera, (Basalt) HalemaumauBasalt Flow Grand Canyon< 1My oldColumnar BasaltBasaltic Eruptions•Low Viscosity•High Temperature (1000 - 1200ºC)•Normally Quiescent Lava Flows–Aa - early, low temperature, blocky flow–Pahoehoe - later high temperature ropy flow–Pillow Lavas - underwater flow•Edifice–Shields–Cinder cones5Famous Volcanoes•Basalts•Dotsero, CO•Kilauea•Mauna Loa•Haleakala•Hekla•Vulcan’s Throne•Andesites•Fuji•St. Helens•Ranier•Shasta•Stromboli•Vesuvius•Popocatepetl•Orizaba•Pelée•Etna•Rhyolites•Yellowstone•Valles/Jemez•Long Valley •Crater Lake•Pinatubo•Krakatao•Santorini•Campi Phlegri (Naples)Most Volcanoes are at Plate BoundariesAndesite Eruptions•Higher viscosity (higher polymerization)•Lower temperature•More water, more explosive•Subduction zone volcanism•Flows–Viscous lava flows–Pyroclastic flows•Edifice–Composite ConesGeologic SettingsWhich volcanic environment will, on average, produce the most felsic (silicic) lavas?A. Mid-ocean ridgeB. Island arcC. Continental arcD. Oceanic hotspotClicker QuestionPlate tectonics explains the global pattern of volcanism.Which volcanic environment will, on average, produce the most felsic (silicic) lavas?A. Mid-ocean ridgeB. Island arcC. Continental arcD. Oceanic hotspotClicker QuestionPlate tectonics explains the global pattern of volcanism.6What composition volcanic rocks characterize magmatism at mid-ocean ridges?A. CarbonatiteB. BasaltC. AndesiteD. RhyoliteClicker QuestionPlate tectonics explains the global pattern of volcanism.What composition volcanic rocks characterize magmatism at mid-ocean ridges?A. CarbonatiteB. BasaltC. AndesiteD. RhyoliteClicker QuestionPlate tectonics explains the global pattern of volcanism.Andesite Flow, Mt ShastaComposite Cone, Mt. Fuji, JapanComposite Cone, Mt. DaisenComposite Cone,Llaima Volcano, Chile7Ash Flow Eruption,Llaima Volcano, ChileComposite Cone, Mt. St Helens8Andesite Eruptions•Higher viscosity (higher polymerization)•Lower temperature•More water, more explosive•Subduction zone volcanism•Flows–Viscous lava flows–Pyroclastic flows (Nuée Ardente)•Edifice–Composite ConesFamous Volcanoes•Basalts•Dotsero, CO•Kilauea•Mauna Loa•Haleakala•Hekla•Vulcan’s Throne•Andesites•Fuji•St. Helens•Ranier•Shasta•Stromboli•Vesuvius•Popocatepetl•Orizaba•Pelée•Etna•Rhyolites•Yellowstone•Valles/Jemez•Long Valley •Crater Lake•Pinatubo•Krakatao•Santorini•Campi Phlegri (Naples)Clicker Question•Which of the following is an example of a basalt volcano?–A. Mt St. Helens –B. Yellowstone–C. Mauna Loa–D. Mt Pinatubo–E. Mt. FujiClicker Question•Which of the following is an example of a basalt volcano?–A. Mt St. Helens –B. Yellowstone–C. Mauna Loa–D. Mt Pinatubo–E. Mt. FujiClicker Question•Which of the following is an example of an andesite volcano?–A. Kilauea –B. Yellowstone–C. Mauna Loa–D. Mt Pinatubo–E. Mt. Fuji9Clicker Question•Which of the following is an example of an andesite volcano?–A. Kilauea –B. Yellowstone–C. Mauna Loa–D. Mt Pinatubo–E. Mt. FujiRhyolite Eruptions•Very high viscosity•Low temperature (600 - 800ºC)•Massive Pyroclastic eruptions–Air fall (pumice)–Ash Flow (Nuée Ardente) Tuff–Obsidian Flows•Edifice–Caldera (5 - 25 km)–Resurgent domeRhyolite Eruptions•Associated Phenomena–Hot Springs–Geysers–Fumaroles•Geologic Setting–Continental Margins and Interiors–Subduction ZonesGeologic SettingsPumice = Glass foamAsh-Flow Tuff with Air-Fall Units (pumice)10Ash-Flow Tuff UnitAsh-Flow Tuff UnitNon-Welded Top Welded CoreVitrophyreNon-welded baseSilicic Tuff Units (Jemez, NM)Obsidian Flow Non-welded Air-Fall UnitsSulfur Fumarole, NysserosCaldera with Cinder ConeCrater Lake, OR11GeyserOld Faithful(Yellowstone)Rhyolite Eruptions•Very high viscosity•Low temperature (600 - 800ºC)•Massive Pyroclastic eruptions–Air fall (pumice)–Ash Flow (Nuée Ardente) Tuff–Obsidian Flows•Edifice–Caldera (5 - 25 km)–Resurgent domeAndesite Eruptions•Higher viscosity (higher polymerization)•Lower temperature•More water, more explosive•Subduction zone volcanism•Flows–Viscous lava flows–Pyroclastic flows•Edifice–Composite ConesBasaltic Eruptions•Low Viscosity•High Temperature (1000 - 1200ºC)•Normally Quiescent Lava Flows–Aa - early, low temperature, blocky flow–Pahoehoe - later high temperature ropy flow–Pillow Lavas - underwater flow•Edifice–Shields–Cinder conesCrater Lake, ORA.BasaltB.AndesiteC.RhyoliteCrater Lake, ORA.BasaltB.AndesiteC.Rhyolite12A.BasaltB.AndesiteC.RhyoliteMt. St.
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