The force of Earth’s movement builds up in rock until it reaches its breaking point, creating a fracture.
Stress acts upon the rock in four different ways, causing the rock to change its shape and size. Tension, when strain pulls rock in opposite directions, causes a rock to stretch, or flatten out.
Compression is the reverse of that, when strain comes at the rock from opposite directions. This elongates a rock vertically.
When the stress hits the rock from all directions it is called uniform stress. The rock then shrinks in size as its particles are squeezed together.
When the rock is compressed from different angles, instead of head-on, the rock will shift diagonally, causing shear stress.