WEATHERING AND MASS MOVEMENT

Weathering is the gradual destruction of rock under surface conditions. Weathering may involve physical processes (mechanical weathering) or chemical activity (chemical weathering). 

Chemical weathering (also known as decomposition or decay) is the breakdown of rock (weathering) by chemical mechanisms, the most important ones:

1. Carbonation

2. Hydration

3. Hydrolysis

4. Oxidation

5. Ion exchange in solution.

Mechanical weathering is the set of various processes of weathering that break apart rocks into particles (sediment).

There are five major mechanisms of mechanical weathering:

1. Abrasion is the grinding action of other rock particles due to gravity or the motion of water, ice or air.
2. Crystallization of ice (frost shattering) or certain minerals such as salt (as in the formation of tafoni) can exert enough force to fracture rock.

1. Thermal fracture is the result of rapid temperature change, as by fire, volcanic activity or day-night cycles (as in the formation of grus), all of which rely on the differences in thermal expansion among a mixture of minerals.
2. Hydration shattering may strongly affect clay minerals, which swell with the addition of water and force openings apart.
3. Exfoliation or pressure release jointing results from the stress changes as rock is uncovered after its formation in deep settings.