Earth's mantle is hottest closest to core. Lower parts of asthenosphere = heat up. Less dense and slowly rise
move towards top of asthenosphere and cool down. More dense , slowly sink
circular movements of semi-molten rock = convection currents
create drag on base of tectonic plates - they move
what is the process of ridge push?
At constructive plate margins , magma rises to the surface , forms new crust (very hot.) Heat expands surrounding rock and rise above surface of surrounding crust , forms a slope
New crust cools , becomes dense. Denser crust = moves downslope due to gravity
Pressure is put on tectonic plates and they move apart
ridge push is also known as?
gravitational sliding
what is the process of sea floor spreading?
As tectonic plates move apart , magma rises to fill gap created. It cools to form new crust
Over time , new crust dragged apart , new crust forms between it
If this happens at plate margins under the sea , the sea floor gets wider
Can create mid-ocean ridges , ridges of higher terrain on either side of the margin
Similar process of spreading occurs at land margins , where plates move apart
