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Lecture 5 Volcanism

Lecture 5 Volcanism. Physical Geology. Lecture Outline. I Characteristics of Volcanoes II Types of Volcanoes A) Shield Volcanoes i. Description ii. Composition iii. Eruption Features B) Composite Volcanoes i. Description ii. Composition iii. Eruption Features

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Lecture 5 Volcanism

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  1. Lecture 5 Volcanism

  2. Physical Geology Lecture Outline I Characteristics of Volcanoes II Types of Volcanoes A) Shield Volcanoes i. Description ii. Composition iii. Eruption Features B) Composite Volcanoes i. Description ii. Composition iii. Eruption Features iv. Distribution C) Cinder Cones i. Description ii. Composition iii. Eruption Features III Lava Floods IV Submarine Eruptions V Living with Volcanoes VI Conclusions

  3. Physical Geology Characteristics of Volcanoes Vent Fumarole Crater Caldera Volcanic Domes

  4. Physical Geology Characteristics of Volcanoes Vents and Fumaroles vent : the opening at the earth's surface through which volcanic materials are extruded. fumarole : a hole or vent from which volcanic fumes or vapors issue.

  5. Physical Geology Characteristics of Volcanoes Craters crater : a basin-like rimmed structure at the top or on the flanks of a volcanic cone; it is formed by explosion or collapse Mt Erebus, Antarctica Mt Poas, Coast Rica Halemaumau, Hawaii

  6. Physical Geology Characteristics of Volcanoes Calderas Aniakchak, Alaska Kaguyak, Alaska Crater Lake, Oregon caldera : a large basin-shaped volcanic depression, more or less circular. the diameter of which is many times greater than that of the included vent or vents, irrespective of the steepness of the walls or the form of the floor.

  7. Physical Geology Characteristics of Volcanoes Caldera Formation

  8. Physical Geology Characteristics of Volcanoes Volcanic Dome volcanic (lava) dome: steep-sided mound built by magma too viscous to flow far from vent before crystallizing and cooling.

  9. Physical Geology Types of Volcanoes Shield Volcanoes Composite Volcanoes Cinder Cones

  10. Physical Geology Types of Volcanoes Shield Volcanoes • Slope: Gentle (2-10o) • Height: up to 10 km • Composition: Flow layers • Basaltic • Eruption: Effusive • Low-Viscosity Lava • A'a • Pahoehoe • Flank Eruptions • Other Characteristics: • Lava Ponds and Tubes • Spatter Cones Mauna Loa, Hawaii

  11. Physical Geology Types of Volcanoes Shield Volcanoes

  12. Physical Geology Types of Volcanoes Shield Volcanoes pahoehoe a'a

  13. Physical Geology Types of Volcanoes Shield Volcanoes lava tube : a hollow space beneath the surface of a solidified lava flow, formed by the withdrawal of molten lava after the formation of a surficial crust spatter cone: A low steep-sided cone of spatter built by lava fountains along a fissure or around a vent

  14. Physical Geology Types of Volcanoes Composite Volcanoes Slope: < 33o Height: 1000 - 4000 m Composition: Layers of pyroclastic fragments and lava flows • Andesitic • Eruption: Explosive • Other Characteristics: • Magma blocks conduit • Glowing clouds Mt St Helens and Mt Ranier

  15. Physical Geology Types of Volcanoes Composite Volcanoes Mount St. Helens May 18, 1980 8:32:00 a.m. The bulging north flank that geoscientists had watched develop since March is intact. It had clearly grown by 450 feet in some areas, and by late April was estimated to be growing at five feet a day. 8:32:10 a.m. A 5.1 magnitude earthquake about 1 mile beneath the mountain causes the north flank to slide. Tendrils of steam burst from the mountain, releasing pressure bottled up in magma below. 8:33:00 a.m. A cubic mile of mountain gives way, traveling at 70 to 150 mph, and superheated rocks in the volcano's core are suddenly exposed, shooting a lateral blast of gas north, incinerating everything in its path. Huge glaciers on the mountain's peak melt instantly. 8:33:20 a.m. The blast is over but the mountain begins to pulverize as the eruption vents its full fury, sending a thick, 3-mile-wide ash cloud 80,000 feet into the sky. http://seattlepi.nwsource.com/mountsthelens/grapherupt.shtml

  16. Physical Geology Types of Volcanoes Composite Volcanoes

  17. Physical Geology Types of Volcanoes Composite Volcanoes http://www.3dnworld.com

  18. Physical Geology Types of Volcanoes Composite Volcanoes

  19. Physical Geology Types of Volcanoes Cinder Cones • Slope: Steep (33o) • Height: < 300 m • Composition: Pyroclastic fragments • Various • Eruption: Explosive • Other Characteristics: • Short-lived Paricutin, Mexico Cinder Cone,Mauna Kea, Hawaii

  20. Physical Geology Lava Floods

  21. Physical Geology Lava Floods The Columbia Plateau

  22. Physical Geology Submarine Eruptions Kavachi, Solomon Islands

  23. Physical Geology Submarine Eruptions The Mid-Ocean Ridge

  24. Physical Geology Volcanic Hazards

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