Answer: Joints form in place, whereas faults form because the rock has moved.
Explanation: A fault is a break in a rock mass along which movement has occurred. A joint is a fracture formed by the movement of the rock in a direction perpendicular to the plane of fracture.
Fault forms when rock above an inclined fracture plane moves downward, sliding along the rock on the other side of the fracture. Normal faults are often found along divergent plate boundaries, such as under the ocean where new crust is forming. Long, deep valleys can also be the result of normal faulting.
A joint is a type of extension fracture formed by the movement of the rock in a direction perpendicular to the plane of fracture. Joints form in solid rock that is stretched and its brittle strength (the point at which it breaks) is exceeded. When this happens, the rock fractures