Gravity, wind or water erosion causes gradual surface decomposition followed by deposition when material from erosion has been transported elsewhere.
Weathering is the chemical and mechanical breakdown of exposed rocks, softening them by altering their minerals, which causes erosion. Erosion then transports these changed rock pieces downstream where they deposit as sediment – thus continuing the cycle of weathering and erosion.
Weathering
Weathering, which refers to the gradual wear-and-tear of rocks and minerals over time, includes rain, wind, ice, plants, animals and humans as all having an influence in this process.
Weathering breaks rocks down into smaller and smaller pieces that eventually become part of the soil. There are two forms of weathering: physical and chemical.
Physical weathering, which involves breaking apart rock without altering its chemical composition, occurs through heat and pressure exposure of cracks in rocks, or stones loosened due to freezing and thawing processes within them. Other examples include ice wedging – when freezing expands and expands back when exposed to air; mechanical weathering caused by flowing streams or rivers and more.
Erosion is the process by which weathered products are transported away from their original site by water. Water plays the biggest part in erosion; it can transport most sizes and types of sediments ranging from microscopic particles to large boulders. Wind and glaciers can also transport sediment, as can gravity.
Erosion
Erosion occurs when natural forces such as water, wind or ice move material from one place to another with ease – similar to how deposition deposits sediment in new places.
Water is one of the primary erosional agents. It erodes rocks through mechanical weathering, seepage into cracks in rocks and freezing and thawing cycles known as frost heaving; and when flowing rapidly down rivers (a process known as flow erosion). When this water moves over sediment-bearing surfaces it forms small channels called rills which later become larger channels known as gullies.
Wind can erode soil, rock and mud by transporting particles far distances; this erosion process has also worn away the edges of mountains by wearing away their summits over time. Furthermore, sediment from rivers or oceans flows down them and deposits it on beaches – this forms part of geologic cycles which have existed for billions of years.
Deposition
Deltas are fan-shaped areas of land formed from sediments deposited by river erosion. Weathering breaks down rocks into sediments which then move downstream with river currents until reaching their destination – usually ocean. Deposition then deposits this material over time, building layers upon layers of sediment over time.
Acid deposition is slowly but steadily decreasing the concentration of sulfur, phosphorous and nitrogen in Adirondack lakes, yet it could take years or decades for these levels to return to their previous levels. Learn more about acid deposition with this NYSERDA resource.
Monitoring nitrogen deposition into forests presents numerous difficulties, such as limited standard measurements and sampling networks accessible only via roads; cost and complexity associated with extracting samples from forest ecosystems; difficulty measuring different forms of N (soluble and fixed). To facilitate better comprehension, this presentation includes several check-for-understanding opportunities and an interactive tableau activity asking students to create scenes depicting weathering, erosion and deposition.
Impacts
Weathering and erosion sculpt the landscape at an almost constant pace. Through natural processes like weathering and erosion, Earth’s rocks are transformed into ever-evolving works of art before they vanish over time.
Erosion is the process of breaking down rocks and minerals near Earth’s surface through physical, chemical or biological means, including transport of fragments via waterways, wind or ice. Erosion may be accelerated by vegetation or animals inhabiting an area as well as glaciers.
Physical weathering, caused by water freezing and thawing cycles in cracks of rock, is one of the primary forms of mechanical weathering. This form of erosion breaks apart rocks into smaller pieces that eventually can form soil.
Water flowing over rocks causes mechanical weathering known as abrasion, where rock fragments collide and grind together, altering their composition over time. The velocity of the water determines the severity of this type of weathering as it erodes rock away; rock species with different levels of erosion resistance such as those at Bryce Canyon National Park in Utah or Goblin Valley State Park also produce distinct geological features like Bryce Canyon’s cliffs or Goblin Valley State Park’s cliffs have distinctive geological features such as those seen at Bryce Canyon National Park or Goblin Valley State Park in Utah.