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Volcanoes

Volcanoes. Dynamic Earth http:// www.youtube.com/watch?v=uZp1dNybgfc. Magma (melted rock inside Earth) bubbles up to Earth’s surface Lava (magma on surface) exits through a vent (opening) Lava cools, solidifies, and builds up to form a mountain (VOLCANO). What is a volcano?.

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Volcanoes

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  1. Volcanoes Dynamic Earth http://www.youtube.com/watch?v=uZp1dNybgfc

  2. Magma (melted rock inside Earth) bubbles up to Earth’s surface • Lava (magma on surface) exits through a vent (opening) • Lava cools, solidifies, and builds up to form a mountain (VOLCANO) What is a volcano?

  3. Crater: bowl shaped depression at top of the volcano surrounding the vent (less than 1 km in diameter) • Caldera: large bowl shaped depression that forms when summit collapses into magma chamber • EX: Crater Lake (Oregon) Craters and Caldera

  4. Shape: large; gentle slope; broad circular base • Lava Type: thin, basaltic lava • Eruption Type: nonexplosive • Example: Hawaiian volcanoes Types of Volcanoes: Shield Volcano

  5. Shape: small with steep sides • Lava Type: thick magma with water and silica • Eruption Type: explosive! • Example: Izalco volcano; El Salvador Types of Volcanoes: Cinder-Cone Volcano

  6. Shape: medium sized; medium steepness • Lava Type: alternating layers of basaltic thin lava and explosive thick lava • Eruption Type: alternating nonexplosive and explosive eruption • Example: Mt. St Helens; Mt. Ranier(Washington) Types of Volcanoes: Composite Volcano

  7. Rock fragments thrown into air during volcanic eruptions; • Classified by size: - Dust - Ash - Lapilli “little stones” -Blocks (large & angular) - Volcanic Bombs (large & rounded; cool in air or on contact with ground) Tephra

  8. Cloud of gas, ash, and tephra that comes from explosive eruption • Travels nearly 200 km/hr • 700 degrees Celsius • Mount Pele on island of Martinique in 1902 killed more than 29,000 people Pyroclastic Flow

  9. 80% at convergent plate boundaries • Ring of Fire: largest ring of volcanic activity around Pacific Plate • 15% at divergent plate boundaries (Mid Atlantic Ridge) • 5% form away from plate boundaries near hot spots • Hot spots: stationary plumes of magma that push up a volcanic island of seamount Where do most volcanic eruptions occur?

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