Geological Agents

The types of crustal movements of the earth include gradation, vulcanism, and tectonism. Gradation has to do with the breaking down of surface rocks due to water, ice or air. This is broken down into two main subdivisions, which are degradation – a wearing down and aggradation – which is a building up by deposition. Usually these two effects are conferred combined under the terminology, weathering, because there is really not any way of separating them effectively. A lot of these forces continue to take place and the process has been occurring for millions of years now. Physical weathering envelops the development when the rocks have been reduced into little fragments without having gone through a chemical composition change. One of the most important reasons of physical weathering is when there are formations of ice in cracks. These, under geological terms are more commonly known as glaciers and their actions are known as ice. Ice formations that take place on a yearly basis are known as frost and this is a process of expansion. The action of frost is divided into two subdivisions, which are frost wedging – in which the ice forms depressions or pockets and makes use of a sideways force, and there is frost heaving that refers to the process when ice is formed in cavities under the earth and makes use of an upward pressure. In cases where the rock does not have a porous area to take in water for the frost action, different type of heating and cooling can facilitate the disintegration of rocks. The alternate expansion and contraction of a surface of rock, even though it is most likely not a big force of disintegration that will cause a lot of influence, will cause there to be little fissures and cracks where frost can get into and can make the process go a lot quicker.

Even though water mostly consists of an agent of deposition, it is also one of the greatest suppliers to gradation. Although water is usually an agent of deposition, it at the same time additionally causes the rock to become eroded. Other agents of erosion also include animals and plants as these cause disintegration of rocks in a lot of different ways. Trees and bushes, as well as little plants in many occasions grow in little crevices in rocks and the roots produce force that spreads and makes the crevices wider and this allows frost pockets to form and in some cases it even pushes the surface of the rock apart causing it to expose more surface to agents that are erosional. The physical effects of weathering that have been mentioned though only cause smaller pieces of the rock and exposes them to other forces of nature that can then carry them and change them as well. Chemical weathering also causes there to be a breakdown in the structure of the rock and on many occasions produced a new mineral. This event is also known as decomposition and the processes that miners are interested in are oxidation, hydration, carbonation, and solution.