A chunk of solid rock in the hand--let alone a snowy peak on the horizon--might seem permanent and unchanging, an indestructible bone of Earth. Yet, like water or organic matter, rocks are constantly transformed. Temperature is an essential part of rock creation, modification, destruction and ultimate rebirth. And, weathering is the first step in the breakdown of rock into smaller fragments. This process is critical to the the formation of landscapes and many other geological processes.
Rocks may decompose or dissolve and at the same time changes in composition through a certain chemical process to form residual materials. This is called chemical weathering. There are three very common chemical processes involved with chemical weathering. First is dissolution which occurs when water such as rain reacts with minerals and dissolving the rock changing its chemical composition. Oxidation is another process wherein oxygen reacts with the minerals in a rock, specifically iron, to form rust. This is why we sometimes see red-colored rocks. Hydrolysis takes effect when water reacts with Feldspar, the most common mineral in rocks, and forms another product, usually clay, that can be easily dissolved later on.
Mechanical weathering
Mechanical weathering happens when rocks disintegrate or breaks down into smaller pieces through physical forces which could be any of the following: exfoliation, abrasion and freeze and thaw weathering. Exfoliation happens when rock sheds off sheets of it along the sheet joints that form by applying pressure on the rock through natural causes such as tectonic activities. Abrasion occurs when rock surface weathers and removes layers of it through friction. The strong wind that constantly rubs on the rock’s surface eventually breaks it down causing it to reduce in size. In cold places where temperatures reach below zero degrees, water that accumulated and froze in between crevices of a rock expands. When time comes that water thaws, it gives more space for more water to sink inside the crevice, and will freeze again. Until such time that rock breaks along such crevice causing the rock to reduce into smaller fragments.
Difference between Chemical Weathering and Mechanical Weathering
Chemical and mechanical weathering are both natural processes that will break down rocks. Their purpose may be the same but their processes are different. Chemical weathering demands chemical reactions with minerals inside the rock and causes changes in rock composition. Sometimes this process will produce a different kind of product due to the reaction. Mechanical weathering only involves the physical breakage of rocks to smaller pieces of fragments. Without changing the physical composition of the rocks, mechanical weathering disintegrates rocks with nature’s own physical pressures.
Climate is very important in the weathering process. Cold temperatures favor mechanical weathering while warm temperatures support chemical weathering. And once weathering is complete, residual materials will be eroded and transported by either wind or water. plant has roots right? So when the plant is inside a crack of a rock and starts growing, the crack is opened up further until finally the rock breaks. This is generally not a very effective mechanism.
Wind can carry abrasive particles which weather rocks. Trees can be uprooted by wind, causing the rocks at their roots to fracture. Wind can create waves which can fracture or exploit an existing fracture in a rock.