Intro to Earth- Geosphere

SJCHS

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GeosphereGeosphere: Land on surface and interior of Earth

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Geosphere

• Lithosphere: cool, rigid shell (made of rocks)• Asthenosphere: part of mantle made of malleable rock • Mesosphere: part of mantle made of solid rock

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Geosphere

• Outer Core: Molten iron and nickel • Causes Earth’s Magnetic field

• Inner Core: Solid iron and nickel

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Plate Tectonics

• Theory of Plate Tectonics: Earth’s lithosphere is fragmented into a dozen plates that are moving

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Plate Tectonics-History

• Early 1900s: Alfred Wegener proposes continental drift • Continents were once one giant land mass (Pangaea) that had separated over time

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Plate Tectonics-Evidence• Continents look like a puzzle with pieces that fit together• The same fossils were found on continents separated by oceans

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Plate Tectonics-Evidence

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Plate Boundaries• Divergent Boundary: Plates are moving apart, forms new crust

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Plate Boundaries• Rifts: Surface cracking, can form oceans• Mid ocean ridges: Newly formed (200 million years old) underwater mountain chains

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Plate Boundaries

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Plate Boundaries

• Convergent Boundaries: One plate sinks under another (subducts); forms trenches, mountains

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Plate Boundaries

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Plate Boundaries

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Plate Boundaries• Transform-fault boundaries: 2 Plates sliding horizontally past each other

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Plate Boundaries• Active volcanoes and earthquakes tend to occur around most plate boundaries

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Cause of Plate Tectonics

• Sea floor spreading or ridge pull: New lithosphere forms at mid ocean ridges (underwater mountains) causing plates to move

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Cause of Plate Tectonics

• Convection in mantle causes motion of plates

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Cause of Plate Tectonics

• Slab pull: As a plate subducts, it pulls the rest of the plate with it due to gravity

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Volcano

• Volcano: A structure made of a combination of cooled molten rock and/or dust/rocks

• Fueled by magma that enters the crust from the mantle when a plate subducts

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Volcano

• Lava: Molten rock• Pyroclastic flow: A combination of hot ash, dust, and gases that travel at high speeds from eruption

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Lava

• Basaltic: Thin lava, dark in color, high in temperature, flows quickly• Rhyolitic: Thicker lava, light in color, lower temperature, flows slowly• Andesitic: In-between other 2 types

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Volcano

• Quiet eruptions: Lava only• Explosive eruptions: Pyroclastic material and lava

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Hot Spots

http://www.pbs.org/wnet/nature/lessons/feeling-hot-hot-hot/video-segments-violent-hawaii/1533/

Earthquake

• Earthquake: When a break between rocks (fault) moves causing ground vibrations (seismic waves)

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Earthquake

• Body Waves: Travel through Earth• P (primary) waves

• Fastest (6 km/s)• Compressional waves: Cause change in volume and density of material

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Earthquake

• S (secondary) waves• Half speed of P waves• Shear waves: Cause change in shape of material

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Earthquake

• Surface waves: travel on surface of Earth• half speed of S waves• Can move ground vertically or horizontally

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Earth Interior

• Can use seismic waves to determine composition of crust, mantle, core• S waves only travel through solids• P waves travel through solids and liquids• P waves travel faster through solids, slower in liquids

Earthquake

• Earthquakes cause damage through shaking and liquefaction• Liquefaction: Soil and sediment behaves like a liquid and cannot support structures

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Earthquake• Tsunami or Seismic Sea Wave

• A fault in the ocean slips or a large underwater land slide occurs• Creates a fast moving wave (500-1000 km/hr)• As waves reach shore, velocity decreases but height increases

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http://www.youtube.com/watch?v=mFsdl7_9l4I

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http://www.youtube.com/watch?v=naQZ0PR3S6w