GEOLOGY

Detailed explanation-1: -At the Earth’s surface, rocks usually break quite quickly, but deeper in the crust, where temperatures and pressures are higher, rocks are more likely to deform plastically. Sudden stress, such as a hit with a hammer, is more likely to make a rock break. Stress applied over time often leads to plastic deformation.

Detailed explanation-2: -When a rock or mineral is subjected to stress, stress is proportional to strain as long as the elastic limit has not been exceeded. This relationship is known as Hooke’s law. Plastic deformation takes place when a rock, mineral, or other substance is stressed beyond its elastic limit (Fig. 1).

Detailed explanation-3: -Rocks under low confining pressures near the earth’s surface therefore generally deform through fracturing and faulting. Rocks deep within the crust under high confining pressures deform by folding.

Detailed explanation-4: -Rocks deforming plastically under compressive stresses crumple into folds (figure 5). They do not return to their original shape. If the rocks experience more stress, they may undergo more folding or even fracture.

Detailed explanation-5: -Rock can respond to stress in three ways: it can deform elastically, it can deform plastically, and it can break or fracture. Elastic strain is reversible; if the stress is removed, the rock will return to its original shape just like a rubber band that is stretched and released. Plastic strain is not reversible.