Chapter 18 Section 3 Notes Volcanoes

Chapter 18 Section 3 Notes Volcanoes - Tephra rock...

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Chapter 18 Section 3 Notes Volcanoes Volcanoes Magma ( melted rock inside the earth) bubbles up to the surface. Lava (magma on the surface) exits through a vent (opening). Lava VOLCANO ) Crater- bowl shaped depression at the top of the volcano surrounding the vent. (usually less than 1 km diameter) Caldera – large bowl shaped depression that forms when summit collapses into magma chamber. Example: Crater Lake (Oregon) Types of Volcanoes Shield volcano Cinder-cone volcano Composite Volcano Shape Large;Gentle slope; broad circular base Small with steep sides Medium sized; Medium steepnesss Lava type Thin, basaltic lava Thick magma with water and silica Alternating layers of basaltic thin lava and explosivethick lava. Eruption Type nonexplosive Explosive! Alternating nonexplosive & explosive eruption Example Hawaiian volcanoes Izalco volcano; El Salvador Mt. St. Helens; Mt. Ranier (Washington)
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Unformatted text preview: Tephra rock fragments thrown into air during volcanic eruption. Classified by size: Dust Ash Lapilli little stones Blocks (large & angular) Volcanic Bombs (large & rounded ; cool in the air or on contact with ground) Pyroclastic flow cloud of gas, ash and tephra that comes from explosive eruption. Travels nearly 200 km/h 700 degrees Celsius Mount Pele on island of Martinique in 1902 killed more than 29000 people. Where do most volcanic eruptions occur? 80% Convergent Plate boundaries Ring of Fire largest ring of volcanic activity around Pacific plate. Mediterranean Belt includes Mount Etna and Mount Vesuvius 15 % Divergent Plate boundaries (Mid Atlantic Ridge) 5% form away from plate boundaries at : Hot Spots stationary plumes of magma that push up a volcanic island of seamount. Hawaiian Island Chain....
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This note was uploaded on 12/25/2011 for the course GEOG 123 taught by Professor Mitchelle during the Fall '10 term at Everglades.

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Chapter 18 Section 3 Notes Volcanoes - Tephra rock...

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