Unit 8:  Internal dynamics of the Earth                                    1   2   3

3.3. Rock deformation

Stresses inside the Earth can cause deformations in rocks. There are three types of stress: compression, tension and shear.

The type of deformation depends on the properties of the materials on which the stress act.

      - Folds

          A fold is a bend in the ground that is produced when plastic materials

        are compressed by stress in the Earth’s lithosphere.

      - Faults

          A fault is a fracture in the rock caused by a displacement of the two volumes

        of rock either side of it. When the rocky blocks do not move, a joint is formed.

Animation: Normal fault (Classzone)

Animation: Reverse fault (Classzone)

Animation: Horizontal fault (Classzone)

3.4. There are several types of faults depending on what kind of stress causes

        them to form. Look at the pictures and indicate in each case the stress

        which has acted and indicate it with arrows.