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Published byMaurice Reynard Cunningham Modified over 8 years ago
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Bell Ringer Wednesday 12/2/09 Explain P waves, S waves, and L waves? At what plate boundaries can volcanoes occur?
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Volcanoes
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Volcanism Volcanism – activity that includes the movement of magma toward or onto the surface of the Earth Magma – liquid rock
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Volcanism Lava – magma that erupts onto Earth’s surface Vent – opening through which molten rock flows onto the surface
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Volcanism Volcano – the vent and volcanic material that builds up on the Earth’s surface around the vent
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Convergent Volcanic Zones Subduction Zones – where oceanic crust goes beneath continental crust
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Convergent Volcanic Zones Pacific Ring of Fire – a major zone of active volcanoes caused by subducting plates encircling the Pacific Ocean
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Convergent Volcanic Zones Island Arc – string of volcanic islands from a deep ocean trench caused by an oceanic crust subducting under another oceanic crust
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Divergent Volcanic Zones Mid-Ocean Ridges – where tectonic plates are moving apart under the ocean (i.e. Iceland)
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Divergent Volcanic Zones Rifts – long, narrow cracks formed at mid- ocean ridges Fissures – cracks through which lava flows
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Hot Spots Hot Spots – area of volcanism within a lithospheric plate
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Hot Spots Hot spots remain stationary while the lithospheric plate moves Example: Hawaiian Islands
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Types of Lava Mafic lava – oceanic crust lava Felsic lava – continental crust lava Pahoehoe – ropey lava
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Types of Lava Aa – sharp, blocky lava
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Types of Lava Pillow lava – round shape lava from ocean
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Volcanic Rock Fragments Tephra – rock fragments from volcano Lapilli – “little stones” (large tephra)
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Volcanic Features 3 types of Volcanic Cones (see fig. 9-p. 744)
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Shield Cone Broad base and gentle slopes Layers of hot mafic lava Hawaiian islands
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Cinder Cone Narrow base and steep slope Layers of tephra Sunset Crater
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Composite Cone Both broad and steep Alternating layers of lava and tephra Mount St. Helens
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Craters and Calderas Crater – funnel shaped pit at the top of the volcano
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Craters and Calderas Caldera – collapse of the volcanic cone creates a large, basin-shaped depression
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Predicting Volcanic Eruptions Clues –Seismographs monitor small earthquakes –Temperature changes within the rock –Slight bulging of volcano surface
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