Earth Sciences

What is erosion?
Answered by Discovery Channel
  • Discovery Channel

    Discovery Channel

  1. Erosion is the geological process in which Earth's surface is worn down by natural forces like running water, wind, glaciers and waves. Erosion breaks down rocks, mountains and land surfaces, and then these broken pieces are carried away by wind, rain or rushing rivers. Even the smaller particles add to the erosion as they move along and pound against exposed earth. Erosion is constantly reshaping the land around us. It's what allows rivers to create channels and deep gorges like the Grand Canyon, and ocean waves to re-create the shores along the coastlines. Glaciers can also cause severe erosion to anything along their paths as they slowly advance and scrape the earth beneath them.

    Determining whether an area will erode depends on four factors: soils, surface covers, topography and climate. The factors are interrelated, but each can affect problems and solutions related to erosion in natural and developed areas. For example, some soils are more susceptible to erosion because they do not let water soak into them, while permeable soils with plenty of organic matter allow rainwater to infiltrate instead of running off, taking more soil with it.  Surface cover refers mostly to whether the soil has vegetation covering it. Shrubs or grasses covering the soil slow water runoff and help water soak into soil. Even mulches and paving help control erosion to some extent.

    Topography affects how -- and how much -- water runs off, which affects overall erosion. Naturally, a long, steep slope causes faster flowing water, as do channels. When soils face south and are exposed, the ground is hotter and drier, so vegetation may not grow as easily there. Climate can cause erosion problems when rain comes in high intensities instead of lighter intensity storms. Snow does not cause erosion, but if the ground constantly freezes and thaws, it can break up soil aggregates that transport in melted snow runoffs [source: State of North Carolina].

    The four factors affecting erosion are largely natural, but man affects many of the factors. Construction -- such as erecting new office buildings or adding subdivisions as part of urban development -- disturbs land and can dramatically accelerate erosion. The loose soil, or sediment, washes into water resources with flowing rainwater. Climate change also is affecting soil erosion. Increased precipitation caused by climate change has added to runoff and melting sea ice caused by global warming has caused more open water. This generates stronger waves that add to erosion of shore lines, along with warmer temperatures and increased storm activity [source: Parry]. Arctic terrain is particularly vulnerable to erosion.

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