Weathering, erosion and deposition are natural processes that shape Earth’s surface. Erosion occurs when rocks or soil are moved from one location to another through forces such as water, wind or glacial ice movement.
Water is one of the primary causes of weathering and erosion, seeping into cracks in rocks before freezing to widen existing gaps between stones further.
Physical Weathering
Physical weathering (mechanical weathering), or mechanical weathering, involves breaking rocks down without changing their chemical makeup or chemical properties. This process may occur through water, ice, wind, plants or changes in temperature.
Even massive rocks crack along natural zones of weakness such as bedding planes in sedimentary rock, exfoliation in metamorphic rocks, or joints in intrusive igneous rocks. When these rocks rise slowly to the surface through uplift and erosion, they become free from overlying pressures and begin weathering naturally.
Physical weathering accelerates chemical weathering by exposing fresh mineral surfaces to attack. Additionally, physical weathering helps break down bedrock cohesion, increasing erosion. Physical weathering and erosion continuously shape Earth’s rocky landscape by shaping canyons and cliffs – for instance through unloading that causes sheeting joints on granite domes, slaking that promotes talus slopes, frost action widening tension cracks behind vertical cliffs as tension cracks widen, frost action widening tension cracks behind vertical cliffs; with physical weathering producing lithic clasts ranging from fine silts/clay particles up to boulders/gravel clasts from very fine silts/clay particles/gravel particles to boulders/gravel particles as lithic clasts produced.
Chemical Weathering
Chemical weathering of rocks occurs when minerals react with oxygen, water or other substances to alter their molecular structures. Carbon dioxide in the air combines with water to form carbonic acid which dissolves rock – this process is known as carbonation and has proven very successful at dissolving limestone in order to form caves such as those at Carlsbad Caverns National Park in New Mexico.
Chemical weathering occurs more rapidly in environments where temperature, humidity and water availability all support an active reaction process. Vegetation also plays an important role in chemical weathering as it produces weak acids that increase dissolution rates and alteration processes.
Chemical weathering alters the shape of land by dislodging material and depositing it elsewhere, a major component of erosion which also includes gravity and mass-wasting processes (see Chapter 10 for details) to transport soil particles from where they were originally deposited to where they eventually settle down.
Biological Weathering
Biological weathering involves the actions of plants, animals, bacteria and fungi to break down rock into soil by adding small particles such as clay, silt or sand to it.
Living creatures can perform biological weathering through both mechanical and chemical forces. Lichnis and mosses are among the most prevalent examples, growing on rocks to erode them further while producing weak acids which further expose their surfaces to physical and chemical weathering processes.
Burrowing animals such as shrews, rabbits and earthworms contribute significantly to biological weathering by digging holes to expose underlying rock that then fractures into smaller pieces. Fungi and lichens that produce chemicals or absorb minerals further degrade its surface while even creating holes on rocks and boulders – though biological weathering tends to be limited in dry regions with limited moisture availability.
Vegetation
Water, wind, ice and plants are natural forces that constantly change our Earth’s landscape by weathering and erosion processes. Through this process rocks become ever-evolving works of art.
Water is one of the world’s most dynamic landscape-altering natural forces. Rivers demonstrate this power by carving their courses through erosion. Furthermore, rivers also deposit sediments during deposition processes which transport them along their courses.
Roots and tunneling animals can also play an integral part in mechanical weathering. One such example is root wedging, in which plant roots penetrate cracks in rock surface to cause further weathering by widening and widening existing fissures over time.
The types of sediment that form depend on the rock’s erosion resistance. Different levels of erosion resistance result in different geological features, like those seen at Grand Canyon cliffs. Erosion of less resistant rocks deposits sediment onto more erosion-resistant materials in graded bedrock sequences creating graded bedrock sequences; this form of deposition is known as turbidite sediment deposition.