Weathering refers to the break down of rocks and minerals caused by natural forces such as temperature and precipitation. Erosion refers to their transportation.
Deposition refers to the act of depositing soft materials that have been eroded through erosion by water, gravity, ice and wind into new locations. Water erosion agents include gravity, wind and ice – but gravity, wind and ice are often the key players here too.
Chemical weathering processes gradually break down rock and mineral fragments into soil through chemical weathering, creating layers. Soil formation depends on several factors including climate (average temperature and precipitation amounts), parent material type, slope of surfaces available for drainage, and time available to form soil layers.
Physical weathering is most prevalent in cold regions, involving cycles of freezing and thawing that gradually break apart rocks. Frost wedging occurs when water seeps into cracks in rocks and freezes before expanding slightly; this creates pressure that causes them to crack further before finally breaking them apart – this process is known as heave.
Frost sorting is another type of physical weathering, in which plant roots wedge their way into cracks in rocks and gradually widen them over a prolonged period, eventually splitting apart rocks by wind or water movement or crack widening. Erosion also removes pieces of Earth to their new location via streams, winds, erosional particles or glaciers carrying pieces with them to their destination.
Root wedging is a form of mechanical/physical weathering which occurs when plant roots force themselves into cracks in bedrock, exerting tremendous pressure upon these fractures as they expand over time and eventually break them apart, thus contributing to soil development and similar to frost wedging in that both cause rock to expand over time.
Streams and rivers play an integral part in physical weathering processes. They serve to transport rocks and sediment to new locations while also producing weak acids (carbonic and sulfuric) that can attack and break down rocks.
Time of exposure to weathering affects how easily rocks erode. Rocks buried quickly become less vulnerable to erosion than those exposed for longer periods. Type of erosion also has an impactful on how quickly a rock breaks down – steep slopes tend to experience much higher rates than gentle ones due to weathering products being washed off more rapidly by rainwater runoff.
Similar to freeze-thaw weathering, salt weathering occurs when salt water enters cracks in rock. Once inside, salt crystals begin to grow and expand as temperature or humidity changes occur, exerting immense pressure on it similar to that of ice expansion and exerting tremendous force against it, much like how freezing and thawing weathering does. As such, mechanical weathering causes rocks to crumble away (see Figure 5.7).
Chemical weathering refers to the disintegration of rocks into smaller particles through exposure. For instance, interlocking silicate grains within granite slowly decay along crystal boundaries until weak spots and cracks form (Figure 6.4). Chemical weathering also leads to halite subefflorescences on rock walls which appear as white areas.
Soil is a loose material formed through the weathering and erosion of rocks, such as at Scotts Bluff National Monument. Soils may form naturally or from transported material deposited elsewhere that is then weathered by wind and water; residual soils typically form in flat, lowland regions with gentle slopes where organic material accumulation occurs naturally.
Chemical weathering occurs when water or other substances react with rocks to alter their composition and weaken or disintegrate them, weakening and disintegrating the rock over time. It tends to occur more effectively in wetter areas with plenty of water nearby and includes three processes; oxidation, hydrolysis and carbonation.
Carlsbad Caverns stands out due to being home to water that contains both calcium ions and acidity; such water has the power to dissolve limestone deposits, leading to cave formation through karst formation – something water can only do so effectively. This makes the experience all the more extraordinary!
Other substances that can weather rocks include volcano ash, carbon dioxide and certain organisms that either live or used to live. Plants, fungi and animals often play an active part in weathering rocks by chewing, burrowing and scratching on them; mechanical weathering speeds up chemical weathering by breaking rocks apart into smaller pieces with increased surface area and thus more chemical reactions taking place simultaneously.