volcanoes and earthquakes
DESCRIPTION
Volcanoes and Earthquakes. Weak spot in crust where molten material (magma) comes to the surface. What is a volcano?. What are plate tectonics ? theory which describes the motions of the earth’s crustal plates What causes plate tectonics ? convection currents in the mantle - PowerPoint PPT PresentationTRANSCRIPT
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Volcanoes and Earthquakes
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What is a volcano?
• Weak spot in crust where molten material (magma) comes to the surface
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Volcanoes and Plate Boundaries• What are plate tectonics? • theory which describes the motions of the earth’s• crustal plates • What causes plate tectonics?• convection currents in the mantle• Volcanic belts around plate boundaries• Ring of Fire
• Converging plate boundaries• Plates come together
• Diverging plate boundaries• Plates seperate
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Hot Spot Volcanoes• Magma erupts through Earth’s crust• Can happen anywhere• Yellowstone
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Volcanic Eruptions• Quiet Eruptions• Low-silica, low-viscosity magma• Hawaii
• Explosive Eruptions• High-silica, high viscosity• Pyroclastic flow• Mt. St. Helens
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Volcano Life Cycle• Active-is erupting or may erupt at any time• Dormant- Might become active in future• Extinct- dead, unlikely to erupt again
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Volcano Energy• Energy comes from magma under Earth• Hot Springs- groundwater heated by magma and forms
pool• Geysers- Hot water, steam erupts from ground• Geothermal energy- water heated naturally• Used to warm houses • electricity (steam)
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What is an earthquake?• Shaking and trembling that results from the movement of
rock beneath Earth’s surface
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Stress in Earth’s Crust
• Tension- stretches rock, divergent• Compression- Squeezes rock until it folds or breaks, convergent
• Shearing- rocks move in opposite directions
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Faults
• Normal Faults- diverge, footwall above hanging wall• Reverse Faults- Compression, hanging wall above
footwall, converge• Strike-slip Faults- plates move past each other
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Seismic Waves
• Carry energy from an earthquake away from the focus (center) through Earth’s interior, and across surface
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Types of Seismic Waves• P waves- first to arrive, longitudinal waves, move in
solids and liquids• S waves- second to arrive, transverse waves, only in
solids• Surface waves- ground moves like ocean waves,
transverse waves
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Seismograph
• Detects seismic waves• Used to map and monitor faults
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Damage from Earthquakes• Shaking- triggers landslides, avalanches, destroys
buildings and water mains• Liquefaction- loose, soft soil turns to mud• Aftershocks- smaller earthquakes following big
earthquake• Tsunamis- large wave