the force that every object exerts on all other objects because of their masses

the amount of mass in a material per unit volume

the brittle, rocky outer layer of Earth

the thick middle layer in the solid part of Earth

the crust and the uppermost mantle are grouped together in a rigid layer called

the plastic (flowing) layer within the mantle

rocks that flow

dense metallic center of Earth

Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other. This is called

forms where two plate collide when the denser plate sinks below the other plate

the circulation of material caused by differences in temperature and density is called

forms where two plates separate

forms where two plates slide past each other

forms where two plates collide

forms where two plates collide making mountains

liquid center of Earth

solid center of Earth

where tectonic plates meet

proposed that the plates slowly moved to their current locations