The rocks that make up mountains have a great variety of lines and swirls that make them unique and beautiful. Have you ever wondered how hard rocks get their patterns? Deformation is any process that affects the shape, size, or volume of an area of the Earth's crust. The type of deformation that occurs depends on the type of stress and the type of rock present in the area of the Earth's crust that you are observing. Rocks aren't stressed out in the same way a college student is stressed out, but they are constantly under pressure that causes them to change their shape over time. Stress is defined as a force applied over an area. If stress is applied uniformly, it is called confining stress and the rock or Earth's crust does not change shape. When the force is not applied equally in all directions differential stress occurs.
he response to stress is also called strain. Rocks will show strain by changing shape, volume, or size. If the area is able to return to its original shape after the strain, it is said to have experienced elastic deformation. If the area does not recover from the change in shape, it has experienced plastic deformation. Let's talk about two types of deformation: When the Earth's crust is folded or bent without breaking, as you can see in, it is called ductile deformation. The curves seen in the rock are the result of ductile deformation. When a rock breaks under stress it is called brittle deformation. As you can see in, the arrows in the figure show a fracture in the rock that is the result of brittle deformation.