C2a

C2a - The structure of the earth

The earth has a layered structure. It is (from out to in):

• crust
• mantle
• core 
• inner core

It's is difficult to get information about the centre of the earth because the deepest mines have only dug a few kilometres into the earth's crust

Scientists rely on studying SEISMIC WAVES to understand the structure of the earth.

Movement of the Lithosphere

the LITHOSPHERE is made of the crust and the top of the mantle

^it is 'cracked' into large interlocking pieces called TECTONIC PLATES:

• Oceanic plates (under oceans)
• Continental plates (form continents)

The plates sit on top of the mantle because they are LESS DENSE than the mantle

The plates move about 2.5cm a year

^cause earthquakes and volcanoes

What causes the plates to move?

Just below the crust, the mantle is quite cold and rigid, and gets hotter and less rigid the deeper you go, which means it can flow.

There are convection currents in the mantle, which causes magma to rise to the surface at plate boundaries

When the molten rock (magma) solidifies, it forms igneous rock. 

This movement of the magma causes the plates to move…