Sci. 4-1

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Sci. 4-1 Inside the Earth Pages 88-94
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A. The Earth is divided into 3 layers.
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1) Crust- outermost layer, thinnest layer a)
2 types of crust- continental crust and oceanic
crust b) Oceanic crust is denser than
continental crust
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2) Mantle- between the core and crust, thickest
layer a) molten rock- magma b) made of mostly
iron and magnesium
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3) Core- center of Earth a) mostly iron
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B. The Earth is divided into 5 main physical
layers 1) Lithosphere- outermost layer, rigid,
broken into tectonic plates
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2) asthenosphere- soft layer of mantle. It is a
rock that, like putty, flows
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3) Mesosphere- lowest part of the mantle, strong
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4) Outer core- liquid part of core 5) Inner core-
solid, dense center of Earth
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C. Tectonic Plates- pieces of the lithosphere
that move around on top of the asthenosphere
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1. The plates are different sizes.
2. They are made of both continental and oceanic
   crusts.

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3) Continental crust does not sink below oceanic
crust because the continental crust is less dense
than oceanic crust. Both crusts are less dense
than the mantle, so they float on top of the
asthenosphere.
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D. Knowledge about the structure of the Earth
comes from the study of seismic waves caused by
Earthquakes.
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1) Seismic waves are vibrations that travel
through the Earth
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2) Seismic waves travel faster through solid rock
than liquid.