The earth’s structure

Earth’s Internal Structure: Compositional Layers

Crustthe outermost solid shell of a

rocky planet

Continental crust

thick (10-70km)- buoyant (less dense than oceanic crust) - mostly old

Oceanic crust

about 25 miles (32 kilometers) thick

- thin (~7 km)- dense (sinks under continental crust)- young

The LithosphereThe crust and the upper layer of the

mantle together

The Lithospheric Plates

The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft,

semi-rigid asthenosphere.

Mantlelayer of the earth between

the crust and the core

Upper mantle

Lower mantle

The Asthenosphere

Largest layer

Convections currents

The Asthenosphere

the semi-rigid part of the middle mantle

flows like hot asphalt under a heavy weight.

Convection Currents

caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again

The middle mantle "flows" because of convection currents.

The Outer Core

composed of the melted metals nickel and

iron.

The Inner Core

Has temperatures and pressures so

great that the metals are

squeezed together and are not able to move about like a

liquid, but are forced to vibrate in place like a solid.

Elements in the crust