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Volcanoes Chapter 6
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6.1 Volcanoes and Plate Tectonics
Volcanoes from along _________________ Both __________________________ Divergent: Plates _______ and allow magma to reach surface Convergent: One plate ______________________ __________ is brought down with the plate and eventually forms magma that rises to the surface plate boundaries divergent and convergent fracture sinks under the other Water
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6.1 Volcanoes and Plate Tectonics
Island arcs Result of ____________________ _______________ plate subducts into deep ocean trench Water in the sinking plate leaves and causes ____________________________________ Magma ______________________ ocean floor to form volcano These volcanoes form ___________________ convergent boundary Older, denser the mantle to melt and form magma rises and breaks through a string of islands
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6.1 Volcanoes and Plate Tectonics
Hot Spots Hot spots _______________________ for millions of years while the earth’s plates move over them Some lie close to plate boundaries and some are ____________________ ________________ formed from a plate moving over a hotspot remain in the same place in the middle of plates Hawaiian islands
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6.2 Volcanic Eruptions crater vent side vent pipe lava flow
magma chamber
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6.2 Volcanic Eruptions Eruptions: Two types of eruptions
____________ rises to surface Dissolved gases in magma ___________________ Pressure in magma __________ and size of bubbles ____________ Force of expanding gases __________________ the volcano to the surface Two types of eruptions _______________ Magma expand and bubble falls increase pushes magma up Quiet Explosive
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6.2 Volcanic Eruptions Quiet Volcanic Eruptions
Magma is _______________ Gases bubble gently Lava oozes quietly and ______________________ 2 types of lava produced and form 2 types of rock: _________________ forms from lava that is fast-moving, thin, and runny. Looks like ropelike coils _________ forms form cooler, thicker lava. Has a rough texture with jagged chunks of lava low in silica can flow many kilometers Pahoehoe Aa
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6.2 Volcanic Eruptions Explosive Volcanic Eruptions
Magma is _________________, thick, and sticky Magma blocks the volcano pipe like a cork Gases are _______________the magma and build up ____________ until the force is great enough to push the magma out volcano Throws lava in the air that cools Smallest pieces are called _________________ Pebble-sized pieces are ________________ Larger pieces that range from gold ball to car size are called ______________ high in silica trapped behind pressure volcanic ash cinders bombs
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6.2 Volcanic Eruptions Volcano Hazards
__________________ cause fires and can bury everything in their path Explosive eruptions send out hot rock and ash, and __________________ Explosive eruptions can also cause ____________ of mud, rock, and melted snow Quiet eruptions pyroclastic flow landslides
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6.2 Volcanic Eruptions Stages of activity: Active (___________):
erupting or will erupt in the near future Dormant (_____________): Expected to become active in the future Extinct (_________): Unlikely to ever erupt again live sleeping dead
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6.3 Volcanic Landforms Landforms from Lava and Ash: Other Landforms:
________________ ___________________ _________________ Other Landforms: ______________ Huge holes left from a volcano that has collapsed Shield volcanoes Cinder cone volcanoes Composite volcanoes Lava plateaus Calderas
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6.3 Volcanic Landforms Cinder Cone Volcanoes
Formed from ____________________with magma that had high silica content Ash, cinders, and bombs ____________________ in a steep, cone-shaped hill or mountain an explosive volcano build up around the vent
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6.3 Volcanic Landforms Composite Volcanoes ________________________
Eruptions alternate between _____________ and explosive with ash, cinders, and bombs Tall, cone-shaped mountain with layers that alternate with _______________ Can be more than ___________________________ The silica content varies lava flows lava and ash 4,800 meters tall
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6.3 Volcanic Landforms Shield Volcanoes
Thin layers of lava come out of a ________ The lava hardens on top of previous layers Wide, gently sloping mountain ____________________ on the ocean floor are usually formed this way vent Hot spot volcanoes
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6.3 Volcanic Landforms Lava Plateaus
Lava flows from several cracks in the earth’s crust Lava is ___________________ so it travels far before it cools and solidifies ________________ with this type of lava flow form high, level plateaus thin and runny Millions of years
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6.3 Volcanic Landforms Landforms from Magma: ________________
Volcanic necks Dikes and sills Dome mountains Batholiths
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6.3 Volcanic Landforms Volcanic Necks
Forms from ___________________ in the pipe of a volcano and then the surrounding rock wears away magma that hardens
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6.3 Volcanic Landforms Dikes Sills Magma forces itself
___________________ and then hardens Sills Magma squeezes ____________________ rock layers and hardens across rock layers between horizontal
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6.3 Volcanic Landforms Dome Mountains
Forms when a large body of hardened magma is __________________________________ The magma forces rock layer to ____________ into a dome shape Rock above the dome mountain wears away, leaving the hardened magma exposed pushed towards the Earth’s surface bend upward
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6.3 Volcanic Landforms Batholiths
A mass of rock formed by a large _________________ cooled inside the crust Millions of years or weathering and erosion wear away the ____________________ and the batholith moves upward _______________ carve the batholith into a mountain body of magma overlying rock Ice and water
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Volcanic Eruptions
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