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EXTRUSIVE IGNEOUS ROCKS What’s your favorite volcano? Volcanoes and Volcanic Rocks 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) Where do volcanoes occur? Do you clean your volcanoes regularly? Where do volcanoes occur? • Plate Boundaries (98%) – Divergent – Ocean-ocean convergent – Ocean-continent Convergent • Hot (wet) Spots 1 Where do volcanoes not occur? Most Volcanoes are at Plate Boundaries • Cratons • Passive continental margins • Oceanic abyssal plains • Continent – continent convergent boundaries Igneous Rock Names and Compositions • Composition Name • • • • Ultramafic Mafic Intermediate Silicic (felsic) • Intrusive • Volcanic Rock Name Rock Name • • • • Peridotite Gabbro Diorite Granite • • • • (Komatiite) Basalt Andesite Rhyolite Magma 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 Boundaries Geologic Settings 2 Basaltic Eruptions Pahoehoe, Hawaii (Basalt) • 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 cones Aa, Hawaii (Basalt) Cinder Cone, Pu’uo’o, Hawaii (Basalt) Pillow Lava, Kauai (Basalt) Most Volcanoes are at Plate Boundaries 3 Cinder Cone + Caldera, (Basalt) Skjaldbreidur Shield, (Basalt) Caldera, (Basalt) Halemaumau Basalt Flow Grand Canyon < 1My old Columnar Basalt Basaltic 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 cones 4 Famous 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) Andesite Eruptions • • • • • Most Volcanoes are at Plate Boundaries Geologic Settings Higher viscosity (higher polymerization) Lower temperature More water, more explosive Subduction zone volcanism Flows – Viscous lava flows – Pyroclastic flows • Edifice – Composite Cones Clicker Question Clicker Question Plate tectonics explains the global pattern of volcanism. Plate tectonics explains the global pattern of volcanism. Which volcanic environment will, on average, produce the most felsic (silicic) lavas? Which volcanic environment will, on average, produce the most felsic (silicic) lavas? A. Mid-ocean ridge B. Island arc C. Continental arc D. Oceanic hotspot A. Mid-ocean ridge B. Island arc C. Continental arc D. Oceanic hotspot 5 Clicker Question Clicker Question Plate tectonics explains the global pattern of volcanism. Plate tectonics explains the global pattern of volcanism. What composition volcanic rocks characterize magmatism at mid-ocean ridges? What composition volcanic rocks characterize magmatism at mid-ocean ridges? A. Carbonatite B. Basalt C. Andesite D. Rhyolite A. Carbonatite B. Basalt C. Andesite D. Rhyolite Andesite Flow, Mt Shasta Composite Cone, Mt. Fuji, Japan Composite Cone, Mt. Daisen Composite Cone, Llaima Volcano, Chile 6 Ash Flow Eruption, Llaima Volcano, Chile Composite Cone, Mt. St Helens 7 Andesite Eruptions • • • • • Higher viscosity (higher polymerization) Lower temperature More water, more explosive Subduction zone volcanism Flows – Viscous lava flows – Pyroclastic flows (Nuée Ardente) • Edifice – Composite Cones Famous 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. Fuji Clicker Question Clicker Question • Which of the following is an • 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. Fuji example of an andesite volcano? – – – – – A. Kilauea B. Yellowstone C. Mauna Loa D. Mt Pinatubo E. Mt. Fuji 8 Clicker Question • Which of the following is an example of an andesite volcano? – – – – A. B. C. D. Kilauea Yellowstone Mauna Loa Mt Pinatubo – E. Mt. Fuji Rhyolite Eruptions 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 dome Geologic Settings • Associated Phenomena – Hot Springs – Geysers – Fumaroles • Geologic Setting – Continental Margins and Interiors – Subduction Zones Pumice = Glass foam Ash-Flow Tuff with Air-Fall Units (pumice) 9 Ash-Flow Tuff Unit Ash-Flow Tuff Unit Non-Welded Top Welded Core Vitrophyre Non-welded base Silicic Tuff Units (Jemez, NM) Sulfur Fumarole, Nysseros Obsidian Flow Non-welded Air-Fall Units Caldera with Cinder Cone Crater Lake, OR 10 Rhyolite Eruptions Geyser • Very high viscosity • Low temperature (600 - 800ºC) • Massive Pyroclastic eruptions Old Faithful (Yellowstone) – Air fall (pumice) – Ash Flow (Nuée Ardente) Tuff – Obsidian Flows • Edifice – Caldera (5 - 25 km) – Resurgent dome • • • • • Andesite Eruptions Basaltic Eruptions Higher viscosity (higher polymerization) Lower temperature More water, more explosive Subduction zone volcanism Flows • Low Viscosity • High Temperature (1000 - 1200ºC) • Normally Quiescent Lava Flows – Aa - early, low temperature, blocky – Viscous lava flows – Pyroclastic flows flow – Pahoehoe - later high temperature ropy flow – Pillow Lavas - underwater flow • Edifice • Edifice – Shields – Cinder cones – Composite Cones Crater Lake, OR Crater Lake, OR A.Basalt A.Basalt B.Andesite B.Andesite C.Rhyolite C.Rhyolite 11 Mt. St. Helens Mt. St. Helens A.Basalt A.Basalt B.Andesite B.Andesite C.Rhyolite C.Rhyolite Kilauea Kilauea A.Basalt A.Basalt B.Andesite B.Andesite C.Rhyolite C.Rhyolite Geologic Settings Most Volcanoes are at Plate Boundaries 12 Famous Volcanoes • • • • • • Basalts Dotsero, CO Kilauea Mauna Loa Haleakala Hekla • • • • • • • • • • Andesites Fuji St. Helens Ranier Shasta Stromboli Vesuvius Popocatepetl Orizaba Pelée • • • • • • • • • Rhyolites Yellowstone Valles/Jemez Long Valley Crater Lake Pinatubo Krakatao Santorini Campi Phlegri (Naples) Volcanic Terms • • • • • • • • • • EXTRUSIVE IGNEOUS ROCKS Ultramafic Mafic Intermediate Silicic Basalt Andesite Magma Lava Aa Pahoehoe • • • • • • Tuff Obsidian Vitrophyre Cone Pumice Cinder Cone Resurgent Caldera dome Pyroclastic • Hot Spring Nuée Ardente • Geyser Air Fall • Rhyolite Ash Flow • • • • • Igneous Rock Names and Compositions • Intrusive • Volcanic Rock Name Rock Name • Composition Name Volcanoes and Volcanic Rocks • Pillow Lava • Shield • Composite • • • • Most Volcanoes are at Plate Boundaries Ultramafic Mafic Intermediate Silicic (felsic) • • • • Peridotite Gabbro Diorite Granite • • • • (Komatiite) Basalt Andesite Rhyolite Famous Volcanoes • • • • • • • Basalts Dotsero, CO Kilauea Mauna Loa Haleakala Hekla Vulcan’s Throne • • • • • • • • • • Andesites Fuji St. Helens Ranier Shasta Stromboli Vesuvius Popocatepetl Orizaba Pelée • • • • • • • • • Rhyolites Yellowstone Valles Long Valley Crater Lake Pinatubo Krakatao Santorini Campi Phlegri (Naples) 13 Volcanic Terms • • • • • • • • • • Ultramafic Mafic Intermediate Silicic Basalt Andesite Magma Lava Aa Pahoehoe • Pillow Lava • Shield • Composite • • • • • • Clicker Not Registered Tuff Obsidian Vitrophyre Cone Pumice Cinder Cone Resurgent Caldera dome Pyroclastic • Hot Spring Nuée Ardente • Geyser Air Fall • Rhyolite Ash Flow • • • • • Clicker Not Registered • McClelland, A • • • • • • Keegan, R. Moten, J. Runyon, K. Scott, G. Shepley, J. Wheeler, S. Clicker Not Registered • McClelland, A • • • • • • Keegan, R. Moten, J. Runyon, K. Scott, G. Shepley, J. Wheeler, S. 14
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