Transcript Plate Tectonics

Plate Tectonics
Chapter 4
Sections 1-3
Pgs. 96-110
Composition of Earth (p.96-97)
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Earth is composed of 3
layers:
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Crust (outermost layer)
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Mantle (middle layer)
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Even though it’s the thinnest
layer, it’s too thick to drill
completely through.
2 types- continental and
oceanic
Hot, convecting = Magma
Can be studied when it
pushes to the surface =
volcanic eruptions
Core (inner layer)
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made mostly of iron = very
dense, metallic
Physical Structure of Earth (p.98-99)
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Earth is divided into 5 physical layers
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Order from outermost to innermost
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Lithosphere- made of crust and upper mantle
Asthenosphere- made of “plastic” part of mantle
Mesosphere- made of strong part of mantle
Outer Core- liquid layer of core
Inner Core- solid layer of core
5 PHYSICAL LAYERS OF THE EARTH (p. 98-99)
Tectonic Plates (p. 100-102)
Pieces of Lithosphere that move around on top of the
Asthenosphere (float like ice in a drink)
 Fit together like a jigsaw puzzle
 Not all plates are the same size
 Can be all oceanic (under water), but many are both
oceanic and continental (some below water and some as
a landmass)
Mapping Earth’s Interior:
 Earthquake’s cause seismic waves that can be measured
using a seismograph.
 Use these measurements to get descriptions of the parts
of the Earth we can’t explore
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Continental Drift (p.104-106)
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Wegener thought all continents were once one, super
continent = Pangaea
Hypothesis states the single landmass broke apart and drifted
to present locations
Force that moves the continents is seafloor spreading- new
lithosphere forms as magma rises to surface and solidifies
Takes place at mid-ocean ridges
Evidence for Continental Drift
& Seafloor Spreading (p.104, 106)
1. Continental drift is supported through the
finding of fossils and examining rock layers
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Plants and animals couldn’t cross the ocean 
continental edges must have met at one time
Rock layers and evidence of ancient climates are
similar on many continents
2. Magnetic reversals are recorded with magnetic
minerals (iron) on ocean floor
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N & S poles change place
Iron comes up in magma through mid-ocean ridges
Plate Tectonics (p.108-109)
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Theory that Earth’s
Lithosphere is divided into
plates that move around on
top of the Asthenosphere
Caused by cycle of heating
rock within the Earth:
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hotter rock rises
then cools becoming more
dense
cooled rock sinks toward center
again
as it approaches the core, it
heats again
CALLED
CONVECTION!
Tectonic Plate Boundaries (p.109)
3 types of boundaries
(boundaries are where tectonic plates touch)
Type
Definition
Possible Outcome
Convergent When 2 plates collide
Divergent
Transform
Folds
Faults
Mountains
When 2 plates separate Seafloor spreading
Mid-ocean ridges
When 2 plates slide past
each other
Earthquake