Download Ch. 7 Plate Tectonics Section 1 Inside the Earth

Ch. 7
Plate Tectonics
Section 1
Inside the Earth
Inside the Earth
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The Composition of Earth
 Crust: outermost layer of Earth
 5-100 km thick
 2 types of crust:
 Continental crust: composition similar to
granite(30 km thick)
 Oceanic crust: composition similar to
basalt (5-8 km thick) denser

Mantle: layer of Earth between crust
and core.
 67% of Earth’s mass
 2,900 km thick

The Core:
 Mostly iron with smaller amounts of
nickel, sulfur, and oxygen.
 33% of Earth’s mass
 Slightly larger than Mars
Section 2
The Restless Continents
Tectonic Plates
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Are pieces of the lithosphere that move
around on top of the asthenosphere.
Wegner’s theory of continental drift
explained many puzzling facts,
including the fit of the Atlantic
coastlines of South America and Africa.
Today’s continents were originally
joined together in the ancient continent
Pangaea.
Section 3
The Theory of Plate Tectonics
Tectonic Plates
Theory of Plate Tectonics
Theory that the Earth’s lithosphere is
divided into tectonic plates that move
on top of the asthenosphere.
 What causes the plates to move?

The process of ridge push, convection,
and slab pull provide some possible
driving forces for plate tectonics.
 Convection is the hot material deep
within the Earth rising to cool.
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Tectonic plate boundaries are classified
as convergent, divergent, and transform.
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Convergent Boundary:

Where plates collide

ex. The Mariana Trench
Divergent Boundary
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Transform Boundary
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Where plates divide
Where plates slide past one another
Data from satellite tracking indicate
that some tectonic plates move up to
3 cm a year.
Plate Boundaries
Convergent, Divergent, Transform
Sea Floor Spreading
Section 4
Deforming the Earth’s Crust
Deforming the Crust
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When rocks change shape due to stress,
the reaction is called deformation.
2 types of stress:
 Compression: when objects are
squeezed or collide together.
 Tension: when objects stretch or
diverge apart.
Folding
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Occurs when rock layers bend due to
stress.
2 types of folds:
 Anticline
 Syncline
Faulting
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Surface along which rocks break and
slide past one another.
Normal Fault: hanging wall moves down
relative to the footwall.
Reverse Fault: hanging wall moves up
relative to the footwall (reverse of normal
fault)
Strike Slip Fault: occur when opposing
forces cause the rock to break and move
horizontally.
Mountain Building

When tectonic plates converge 3 major types
of mountains are made.
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Folded Mountains: form when rock layers are
squeezed together and pushed upwards.
Fault Block Mountains: form when normal faults
cause large blocks of Earth’s crust to drop down
relative to other blocks.
Volcanic Mountains: form when molten rock
erupts onto Earth’s surface.