Cambridge as Level Weathering Process

Weathering Process Physical Weathering Processes Freeze Thaw (Frost Shattering) Temperatures strike to fluctuate above and below freezing. When the temperature drops below 0 degrees, irrigate collected in contestation cracks freezes and expands. When temperatures elevate again the ice melts. Pressure created by expansion results in progressive weakening of the rock. At full(prenominal) altitudes frost-shattered material forms scree slopes. Heating & Cooling Thermal expansion & contraction of rock in chemical reaction to rising and falling temperatures. The daily cycle of heating and cooling sets up stresses in the rock that establish it to disintegrate.Occurs mostly in deserts where there is the greatest diurnal temperature range. Also occurs during bush fires. Wetting & Drying (Slaking) escape from is alternately wetted then dried. Minerals which make up clay rocks expand when wetted, then contract on drying-out. The stresses from repeated expansion and contraction cause th e rock to disintegrate. This process commonly occurs on the intertidal zone of coasts. scale (Onion weathering/Spheroidal) Under warm conditions rock surfaces heat up and expand more than the main mass of the inwrought body of the rock.Eventually the surface layers split off or spall from the lower layers, sometimes in fairly curved sheets like the layers of an onion. Seen especially in granite. Crystal Growth (Salt Weathering) Salt crystals, such as sodium carbonate and magnesium sulphate grow within spaces in a rock. It happens when saline water enters cracks in rocks then evaporates. The growing crystals prise the rock apart and small pieces break off. This process is especially good in semi-arid areas and coastal regions. Pressure Release (Dilation) Not caused by elements of weather.Occurs either when erosion removes a heavy(a) covering of rock or when large ice sheets melt. The removal of great weight allows the rock layers down the stairs to expend. As they expand they a lso fracture to produce render planes parallel to the ground surface. The spaces between the bedding planes (joints) are now open to the influence of further weathering. Organic Action The breaking up of rock by plant roots and burrowing animals. Roots grow into cracks and lines of weakness & as they thicken exert increase pressure and cause rocks to fracture.Chemical Weathering Processes Hydrolysis The most common chemical weathering process. Carbonic acid in rain water releases hydrogen ions from the water which then combine with minerals in rocks causing them to break down. This is common in rocks containing feldspar e. g. granite. The end products weathered feldspar are clay minerals known as kaolinite. Kaolinite is an important component of ticket bone China. Hydration This occurs when water is absorbed into the crystal structure of certain minerals and causes chemical changes e. g. nhydrite absorbs water to kick the bucket gypsum which is fleecy and crumbly. Carbonation O n contact with calcium carbonate (the main component of limestone), carbonic acid found in rain water creates calcium bicarbonate. As calcium bicarbonate is readily dissolved in water it is quickly transported away, leaving behind only the clay and quartz impurities of the limestone. This process is most common in regions with limestone geology. Solution Some minerals in rocks do not require a chemical reaction to become soluble e. g. rock slat readily dissolves in water. OxidationSome minerals in rocks react with oxygen dissolved in water to form oxides This process commonly occurs in rocks containing iron. Iron in its ferrous from is changed by oxidisation into its ferric from leading to the collapse of tis molecular structure. Commonly this is known as rust. Chelation Lichens and decomposing organic be in soil (humus) release organic acids. These acids attack certain minerals in rock, releasing iron and aluminum ions which are then transported way by water. The process of relea se is called chelation and the organic acids are known as chelating agents.