Sci. 4-1 Inside the Earth Pages 88-94

A. The Earth is divided into 3 layers.

1) Crust- outermost layer, thinnest layer a) 2 types of crust- continental crust and oceanic crust b) Oceanic crust is denser than continental crust

2) Mantle- between the core and crust, thickest layer a) molten rock- magma b) made of mostly iron and magnesium

3) Core- center of Earth a) mostly iron

B. The Earth is divided into 5 main physical layers 1) Lithosphere- outermost layer, rigid, broken into tectonic plates

2) asthenosphere- soft layer of mantle 2) asthenosphere- soft layer of mantle. It is a rock that, like putty, flows

3) Mesosphere- lowest part of the mantle, strong

4) Outer core- liquid part of core 5) Inner core- solid, dense center of Earth

C. Tectonic Plates- pieces of the lithosphere that move around on top of the asthenosphere

The plates are different sizes. They are made of both continental and oceanic crusts.

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.

D. Knowledge about the structure of the Earth comes from the study of seismic waves caused by Earthquakes.

1) Seismic waves are vibrations that travel through the Earth

2) Seismic waves travel faster through solid rock than liquid.