Weathering and erosion constantly alter Earth’s rocky landscape. When rocks weather away they form sediments which then get transported by erosion to new locations – creating rivers, oceans, lakes and meanders along their journeys.
What is Weathering Erosion and Deposition? Erosion involves breaking apart rocks to move them to other parts of their respective locations. Deposition involves gathering these broken down rock fragments together into larger ones before depositing them somewhere new.
Physical
Weathering, erosion and deposition are natural processes that sculpt Earth’s rocks and minerals into breathtaking landscapes, with lasting consequences on water supplies, climate, biodiversity and local biodiversity.
Rocks and minerals disintegrate through chemical and physical interactions with air, water, and living organisms, becoming broken-down rock particles which are transported via erosion to be deposited elsewhere in their new locations by deposition.
Weathering, erosion and deposition have had an immense influence on our environment for thousands to millions of years, shaping magnificent landscapes such as Grand Canyon in Arizona and Bryce Canyon in Utah as well as altering its topography, altering river sedimentation patterns, creating beaches along shorelines deposits and altering topographies worldwide.
Mechanical weathering occurs through wind, water and ice breaking down rock surfaces to expose fresh surfaces for grinding by expanding ice; other forms include freeze-thaw weathering which results in shattering, fractures and grinding of rocks surfaces by expanding ice; frost wedging (expansion and shattering of rocks through fractured bedrock cracks); water erosion is the predominant force altering mountainous landscapes as it transports, grinds and erodes rocks before discharging sediment into deep ocean basins.
Chemical
Chemical weathering occurs when elements like water, air, sunlight, ice, salts, plants and changes in pressure combine with elements like sunlight to break down rocks and break apart minerals contained within. Chemical weathering may dissolve minerals in a rock’s composition or make its surface softer so as to be easily broken apart; for example iron may erode into rust before disintegration occurs and leaving behind sand, silt and gravel (figure 8-17).
Chemical weathering can produce breathtaking landscapes like Shilin or the Stone Forest near Kunming in China. Here, hundreds of weathered limestone towers protrude from the ground.
Erosion involves the wind, water or ice entrainment and transport of sand, silt and gravel from their original locations to new ones by wind, water or ice currents. Once transported, this material is then deposited elsewhere – either close by at the bottom of a hill for instance or miles away such as river deltas – where deposition starts the clock for soil formation as well as carrying harmful chemicals which pollute our environment.
Biological
Water-generated deposits of sand, silt or gravel.
Erosion occurs when weathering of rock breaks it into smaller pieces that are then carried away by gravity, water, ice or wind forces.
Living organisms can also contribute to erosion. Plant roots may get wedged into small cracks in rocks (a form of mechanical weathering), then as they grow they widen them further and pull apart the rock surface.
Minerals in soil and the water around rocks can aid chemical weathering. Certain plant compounds produce acids which speed this process. Acid rain from burning coal, oil and gas releases chemicals which dissolve into water and form acids which attack rocks quickly.
Ice’s freeze-thaw cycle can also break apart rocks through frost weathering or cryofracturing; one huge boulder in New Zealand was split apart by this physical weathering phenomenon.
Economic
Weathering erosion and deposition are dynamic forces constantly altering Earth’s landscape. Through erosion we see cracks appear in roads and sidewalks while beaches become exposed with their exposed shorelines becoming littered with sand deposits. Erosion also transports pollutants such as chemical fertilizers and pesticides into other locations where they may pose environmental threats.
Weathering and erosion break down rocks into smaller particles that are easily transported or deposited by wind, water, ice or gravity; these materials are known as sediments.
Weathering refers to the physical and chemical breakdown of rock at its original site, while erosion refers to its transportation by water, ice, wind or gravity. Eroded sediments deposited become sedimentary rocks; while those carrying valuable nutrients such as sand can enrich soil for plants. A study estimated the value of these nutrients at $900 million each year (Bertol 2017).