What are three differences between brittle and plastic strain (may include both characteristics of the strain as well as the conditions and locations where each type of strain occurs), and give an example of the type of structure (deformation feature) associated with each type of strain. Make sure you clearly identify which type of strain is associated with each different trait and feature.

elastic deformation: the rock returns to its original shape when the stress is removed.

plastic deformation: the rock does not return to its original shape when the stress is removed.

fracture: the rock breaks.

Explanation:

Stress is the force applied to an object. In geology, stress is the force per unit area that is placed on a rock. Four types of stresses act on materials.

A deeply buried rock is pushed down by the weight of all the material above it. Since the rock cannot move, it cannot deform. This is called confining stress.

Compression squeezes rocks together, causing rocks to fold or fracture (break) (figure 1). Compression is the most common stress at convergent plate boundaries.

Rocks that are pulled apart are under tension. Rocks under tension lengthen or break apart. Tension is the major type of stress at divergent plate boundaries.

When forces are parallel but moving in opposite directions, the stress is called shear (figure 2). Shear stress is the most common stress at transform plate boundaries.

Stress In Earth’s Crust

Enormous slabs of lithosphere move unevenly over the planet’s spherical surface, resulting in earthquakes. This chapter deals with two types of geological activity that occur because of plate tectonics: mountain building and earthquakes. First, we will consider what can happen to rocks when they are exposed to stress.