The mediums required to for material displacement can be wind, running water, waves, ice glaciers , underground water, and gravity. Differences in atmospheric pressure will cause the motion of air that can erode surface material when velocities are high enough to move particles. Eolian erosion is more pronounced in dry regions and in areas where there is insufficient rainfall to support vegetation and root systems. Wind cannot carry as large particles as flowing water, but easily pick ups dry particles of soil, sand and dust and carries them away.
Abrasion is the process of erosion produced by the suspended particles that impact on solid objects. Windblown grains of sand, carried along at high speed, are a very effective tool that can sandblast away rocks by abrasion.
When top soil is gone, erosion can cause rills and gullies that make the cultivation of paddocks impossible. Erosion has created a gully in this paddock, exposing the subsoil lighter coloured soil , and making it difficult to cultivate. Queensland farmers have been cultivating the land since the s.
However, early farmers were not aware that some of their farming practices were causing erosion. By the s, soil erosion was seriously threatening the productivity of fertile cropping areas such as the Darling Downs and the Inland Burnett. If nothing is done to protect the soil, losses can be very high.
Soil erosion has been so severe that some areas of Queensland are now unsuitable for cropping. Soil losses from unprotected cultivation in upland cropping areas of the Darling Downs can average between 20 and 60 tonnes per hectare per year.
Steep, unprotected cropping lands in tropical areas can lose up to tonnes of soil per hectare per year. The next day, under the beating sun, the ice melts and trickles the cracked fragments away. Repeated swings in temperature can also weaken and eventually fragment rock, which expands when hot and shrinks when cold. Such pulsing slowly turns stones in the arid desert to sand. Likewise, constant cycles from wet to dry will crumble clay. Bits of sand are picked up and carried off by the wind, which can then blast the sides of nearby rocks, buffing and polishing them smooth.
On the seashore, the action of waves chips away at cliffs and rakes the fragments back and forth into fine sand. Plants and animals also take a heavy toll on Earth's hardened minerals.
Lichens and mosses can squeeze into cracks and crevices, where they take root. As they grow, so do the cracks, eventually splitting into bits and pieces. Critters big and small trample, crush, and plow rocks as they scurry across the surface and burrow underground. Plants and animals also produce acids that mix with rainwater, a combination that eats away at rocks.
Rainwater also mixes with chemicals as it falls from the sky, forming an acidic concoction that dissolves rock. Back up on the mountains, snow and ice build up into glaciers that weigh on the rocks beneath and slowly push them downhill under the force of gravity. Together with advancing ice, the rocks carve out a path as the glacier slumps down the mountain. When the glacier begins to melt, it deposits its cargo of soil and rock, transporting the rocky debris toward the sea.
Every year, rivers deposit millions of tons of sediment into the oceans. Without the erosive forces of water, wind, and ice, rock debris would simply pile up where it forms and obscure from view nature's weathered sculptures. Although erosion is a natural process, abusive land-use practices such as deforestation and overgrazing can expedite erosion and strip the land of soils needed for food to grow. All rights reserved. Share Tweet Email.
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