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Weathering and erosion

Review your understanding of weathering and erosion in this free article aligned to NGSS standards.

Key points:

  • The movement of water can create and modify features on Earth’s surface. This happens through weathering, erosion, and deposition.
  • Weathering occurs when water breaks down rocks and soil to create sediment. There are two main types of weathering: mechanical and chemical.
    • Mechanical weathering is the creation of sediment through physical means. For example, a stream can dislodge soil particles from its banks.
    • Chemical weathering is the creation of sediment through chemical means. For example, acid rain can react with rocks, dissolving them.
  • Erosion occurs when water transports sediment from one place to another. For example, a river can carry mud downstream. In general, water has more erosional power when it flows faster and has more volume.
  • Deposition (also called sedimentation) occurs when water drops sediment in a new location. For example, ocean waves can deposit sand on a beach.
Fjaðrárgljúfur, a canyon in Iceland, was created over millions of years by weathering and erosion from flowing glacial water. Image credit: “Fjaðrárgljúfur canyon” by kzoop, CC BY-NC-ND 2.0.

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