Weathering, erosion and deposition are forces which shape Earth’s landscape, slowly chipping away at rocks until they reveal ever-evolving masterpieces of art.
Water, wind, ice and gravity are the forces responsible for weathering, erosion and deposition. We witness their action every day when we notice fractured roads or sidewalks created by expanding ice or raindrops pounding onto rocks.
Water
The Grand Canyon in Arizona is a five-thousand-foot deep chasm formed over millions of years by erosion deposition processes caused by weathering erosion deposition processes.
Water and wind are two primary ways that pieces of Earth move around to different spots on our planet, which is known as erosion. Erosion can either be physical or chemical in nature.
Physical erosion involves changing the size or shape of rocks without altering their basic chemical makeup. Examples of physical weathering include waves eroding the base of hills, wind blowing sand across desert playas and plant roots pushing their way between cracks in rocks.
Chemical weathering weakens rocks through processes like freezing and thawing, or when reacting with oxygen. Chemical weathering also occurs when exposed to air that contains sulfur dioxide, nitrogen dioxide and carbon dioxide – three chemicals known to form acid rain that is particularly destructive to rocks. Erosion caused by chemical weathering typically happens more slowly than physical erosion.
Ice
Admiralty Inlet on Baffin Island in Canada features a waterfall that cascades over rocks. Water and ice play an integral role in weathering and erosion processes that transform Earth’s rocks into ever-evolving works of art.
Water freezes into cracks in rocks and expands when it warms back up, widening and deepening those same cracks over time. Over time, this ice wedging process can eventually break apart rocks or even mountains altogether. Plants also help weather rocks by growing in their pores – forcing rocks farther apart while creating chemical changes to the rock itself.
Once rock has been broken down through weathering, its fragments may be carried away by erosion and deposited elsewhere. Erosion is caused by wind, water, ice and gravity and results in sediment being left behind – this sediment may contain dirt, sand or small pieces of rock; once deposited it may build up as hills or sandbars; alternatively it can wash into rivers or oceans to become part of their sea floor.
Wind
Wind can be an immensely powerful force of nature that causes weathering and erosion. Wind currents pick up particles of rock and soil from one location and deposit them somewhere else; erosion may take place quickly – as with mudslides – or slowly over time as stream beds form over time.
Streams complete the hydrologic cycle by returning rain that falls on land to oceans. Their flowing waters may cause both chemical and mechanical weathering as well as transport sediments.
Streams typically contain materials eroded from other areas, including rocks and sand that has been washed downstream, known as clastic sediments, that often feature fine-grained particles with dark hues, like those seen on some beaches with black sands. They may also carry silt and mud that has been deposited by gravity or wind; such deposits are called “clastic deposits”.
Plants and Animals
Weathering and erosion can be seen everywhere — from cracks in sidewalks to the beach sand. Biogeology is the study of this interaction between living organisms and nonliving features.
Erosion occurs when weathered particles are transported away by wind, running water like rivers and glaciers or even living things such as plant roots wedged between cracks in rocks or herbivorous fish grazing coral reefs and grinding off pieces that become deposited as sand.
Some erosion occurs quickly, such as when a boulder rolls down a mountainside; other instances take more time, like when waves erode coastal rock formations. Gravity is the main force responsible for erosion; however, other forces may speed it up; for instance melting snow and ice and blowing it away can accelerate this process of degradation.