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Earth's

Layers

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|| Outer Core

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|| Inner Core

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Convection Currents In the Mantle

Convection currents in the mantle are movements of material heating up, rising, cooling down, and sinking back down. This is caused by the heat of the core. They are very important to the plate tectonic theory because they drive the plate tectonics.

Continental Drift

Alfred Wegener was a geophysicist that proposed the theory of continental drift. This theory stated that the continents were gradually moving away from each other over time, and were once connected as ....................................one continent called Pangaea. ......................................................................... Scientists were ............................................................................... doubtful of this .................................................................................... theory because ..................................................................................... Wegener could ..................................................................................... not prove why ....................................................................................the continents ................................................................................drifted.

Continental Drift Evidence

.............................Continents fit .............................together like .............................puzzle pieces.

Plant and animal fossils were found in similar areas on different continents.

Land formations matched up with other continents

Glacial deposits were found in unusual areas

Seafloor Spreading

Harry Hess was a geologist that proposed the seafloor spreading theory. This theory was very important because it proved Alfred Wegener's continental drift theory. Due to volcanic activity, oceanic crust is formed at mid-ocean .....................................................................ridges. The new .....................................................................crust is then .....................................................................pushed away from .................................................................... the ridge and later .....................................................................gets pushed under .....................................................................either continental .....................................................................or oceanic crust.

Seafloor Spreading Evidence

-Eruption of molten material was found at the mid-ocean ridge.

-Differing magnetic polarities in the seafloor.

-The age of the seafloor was older further away from the mid-ocean ridge.

Plate Tectonics

The plate tectonics theory describes the motion of 7 large plates and numerous other smaller plates of the Earth's lithosphere. The motion of where they meet determines the type of plate boundary: convergent, divergent, or transform. Mountains, trenches, and volcanoes form at these boundaries.

Compression

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Types of Stress

Tensile Stress:

-Force that pulls crust in the opposite direction.

-Causes crust to stretch and become thin in the .middle.

Compressive Stress:

-Force that pushes rock together.

-Causes crust to rise in the middle.

Shear Stress:

-Force that pushes crust together in opposite directions.

-Causes masses of rocks to break, slip, or change shape.

Types of Stress (Graphics)

Tensile Stress:

Compressive Stress:

Shear Stress: