internal structure of the earth plate tectonics sea floor spreading
TRANSCRIPT
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Internal Structure of the Internal Structure of the EarthEarth
Plate TectonicsPlate Tectonics
Sea Floor SpreadingSea Floor Spreading
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Internal Structure of the EarthInternal Structure of the Earth
The Earth has four internal layers:
• Crust
• Mantle
• Outer core
• Inner core
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Earth’s InteriorEarth’s Interior
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How do we know there are four How do we know there are four layers?layers?
• We don’t, it’s a theory!
• Using earthquake waves, they can tell whether an object is a liquid or a solid, so by using that information, they theorized about the interior layers of the Earth
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Seismic waves and the Earth’s Seismic waves and the Earth’s InteriorInterior
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Layers of the EarthLayers of the Earth
• Crust– Made out of ocean crust or continental crust– Thinnest layer– The one we live on– We have never dug through this layer
• Ocean crust: Dark, dense, and thin
• Continental crust: Light, less dense, and thicker
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Ocean Vs. Continental CrustOcean Vs. Continental Crust
Basalt = Ocean Crust
Granite = Continental Crust
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MantleMantle
• The mantle is the thickest layer• The material is similar to Jello—not quite a solid,
but not a liquid either• The elasticity of the substance allows the plates
to move around the planet• The mantle is broken into two parts
– Lithosphere: upper mantle and crust– Asthenosphere: lower mantle
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Outer Core/Inner CoreOuter Core/Inner Core
• The outer core is made out of liquid Iron and Nickel
• The inner core is a solid layer made out of Iron and Nickel
• Both layers make up the majority of the weight of the planet
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Theory of Continental DriftTheory of Continental Drift
• The theory that continents drifted across the ocean to get their current spots on the globe.
• First suggested by Alfred Wegner
• First used the idea of one super giant continent called Pangaea.
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Evidence?Evidence?
• What was the evidence behind Wegner’s idea?
• The continents fit together like puzzle pieces.
• The fossils and rocks on separate continents being identical.
• Climate regions (found by looking at fossils) that did not match up with the positions the continents are located today.
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What made it go?What made it go?
• Wegner believed that the continents floated on the waters of the ocean to get to their current locations.
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Theory of Seafloor SpreadingTheory of Seafloor Spreading
• Molten material rises at the Mid-Ocean Ridge.
• The material flows away from the ridge, carrying the land that was once together, further apart.
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Theory of PLATE TECTONICSTheory of PLATE TECTONICS
• First accepted in 1968 by a man named Hess.
• Combined the ideas of seafloor spreading and continental drift.
• States that the Earth’s crust and upper mantle are broken into sections called plates.
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Why do the plates move?Why do the plates move?
• Hot magma from within the Earth rises to the surface then cools down and sinks back into the Earth.
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What makes the plates move?What makes the plates move?
1. New seafloor is created and spreads out.
2. The continents on either side begin to move away from each other.
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What makes the plates move?What makes the plates move?
3. Dense seafloor hits continental land.
4. Denser floor goes into the mantle and melts.
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How do the plates move?How do the plates move?
• The plates move in three different ways:
• Collide
• Separate
• Slide past each other
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Convergent PlatesConvergent Plates
Continent vs. Ocean• The more dense ocean
plate slides under the less dense continental plate – called Subduction
• Chains of volcanoes are formed along the edge of continents. Also trenches are formed off the coast of the continent.
• The Cascade Mountain chain is formed this way.
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Convergent PlatesConvergent Plates
Ocean vs. Ocean• Both dense plates are
pushed towards the center of the Earth
• Extremely deep trenches are formed, and also chains of volcanic islands are created (island arcs)
• The Japanese Islands are formed this way.
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Convergent PlatesConvergent Plates
Continent vs. Continent• When two continental plates
hit both plates are forced up. No subduction occurs.
• Mountains are formed, not volcanoes.
• The Himalayan Mountains in India are formed this way.
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Transform BoundaryTransform Boundary
• When one plate slides past another.
• The most famous is the San Andreas fault in California.
• No creation of anything, just destruction.
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Divergent BoundaryDivergent Boundary
• When two plates separate from each other.
• The Mid-Atlantic ridge is the best example.