Weathering, Erosion, and Deposition

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Weathering Noun

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[weth-er-ing]

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Weathering

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The physical and chemical breakdown of rocks into smaller pieces, called sediments, at or near the Earth's surface.

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Example: A tree's roots grow into cracks in rock, and as the roots expand, they exert pressure that breaks the rock apart.

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Erosion Noun

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[ee-roh-zhun]

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Erosion

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The process of removing and transporting weathered material from one location to another by agents like water, wind, and ice.

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Example: This image defines erosion as the movement of rock and soil, and shows the main causes, or agents, of this process: water, wind, ice (glaciers), and human activity.

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Deposition Noun

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[dep-uh-zish-un]

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Deposition

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The process where eroded sediments are laid down or settle in a new location when an agent of erosion loses energy.

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Example: This diagram shows a river slowing as it enters a lake, causing it to drop sediment and build up layers of land called a delta.

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Sediments Noun

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[sed-uh-munts]

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Sediments

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Naturally occurring rock particles of various sizes, from boulders to clay, that are formed by the process of weathering.

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Example: Water flow moves sediments in different ways: small particles are carried in suspension, while larger rocks are rolled (traction) or bounced (saltation) along the bottom.

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Mechanical Weathering Noun

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[muh-kan-i-kuhl weth-er-ing]

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Mechanical Weathering

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The physical breakdown of rocks into smaller pieces without changing the rock's chemical composition or mineral content.

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Example: A tree's roots grow into cracks in rock, and as the roots get bigger, they exert pressure that physically breaks the rock apart.

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Chemical Weathering Noun

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[kem-i-kuhl weth-er-ing]

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Chemical Weathering

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The breakdown of rocks through chemical reactions that change the rock's mineral composition and create entirely new substances.

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Example: This image shows four types of chemical weathering: water dissolving rock to form caves, oxygen causing rocks to rust, acid creating pits, and organisms like lichen breaking down rock surfaces.

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Frost Wedging Noun

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[frost wej-ing]

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Frost Wedging

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A form of mechanical weathering where water freezes and expands in rock cracks, prying the rock apart over time.

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Example: This diagram shows how water seeps into a rock crack, freezes to become ice, and expands, which forces the crack to widen and eventually break the rock apart.

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Abrasion Noun

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[uh-brey-zhun]

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Abrasion

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The grinding and wearing away of rock surfaces through the mechanical action of other moving rock or sand particles.

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Example: This diagram shows a glacier moving, with rocks embedded in its base scraping and grinding against the bedrock below, which is the process of abrasion.

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Exfoliation Noun

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[eks-foh-lee-ey-shun]

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Exfoliation

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A mechanical weathering process in which large, curved sheets of outer rock layers are stripped away from a rock body.

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Example: This image shows large, thin sheets of rock peeling off a larger rock formation, which is the process of exfoliation.

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Oxidation Noun

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[ok-si-dey-shun]

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Oxidation

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A chemical weathering process where oxygen combines with minerals, especially iron, causing them to rust and weaken the rock.

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Example: This image shows that oxidation is a chemical weathering process where iron reacts with oxygen and water to form rust, a new substance.