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Earth Science
How Erosion Changes Landscapes
Erosion Changes Landscapes
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Erosion is the movement of rock, soil, and sediment from one place to another by water, wind, ice, or gravity. It matters because erosion carves valleys, shapes coastlines, lowers mountains, and builds new landforms such as deltas and sandbars. The landscapes we see today are snapshots of slow processes that have acted for thousands to millions of years. Understanding erosion helps people predict hazards, protect soil, and manage rivers, beaches, and slopes.
Key Facts
- Erosion moves sediment, while weathering breaks rock into smaller pieces.
- Stream power increases when water velocity or discharge increases: more speed means more erosion.
- Sediment load is the amount of material carried by water, wind, or ice.
- Glaciers erode by plucking and abrasion as ice drags rock across the ground.
- Wind erosion is strongest in dry areas with loose sediment and little vegetation.
- Average erosion rate = thickness removed / time, such as 30 cm / 1000 yr = 0.03 cm/yr.
Vocabulary
- Erosion
- Erosion is the transport of rock, soil, or sediment by moving water, wind, ice, or gravity.
- Weathering
- Weathering is the breakdown of rock into smaller pieces by physical, chemical, or biological processes.
- Deposition
- Deposition is the dropping or settling of sediment when the transporting force loses energy.
- Abrasion
- Abrasion is the scraping and grinding of rock surfaces by sediment carried by water, wind, or ice.
- Glacier
- A glacier is a large, slow moving mass of ice that forms on land and can erode valleys as it flows.
Common Mistakes to Avoid
- Calling erosion and weathering the same thing is wrong because weathering breaks material apart, while erosion moves it to a new location.
- Assuming erosion only happens during disasters is wrong because rivers, waves, wind, and glaciers can reshape land slowly every day.
- Thinking bigger rocks always travel farther is wrong because large particles usually need more energy to move and often settle before smaller particles.
- Ignoring deposition is a mistake because erosion does not just remove land, it also builds new features when sediment is dropped.
Practice Questions
- 1 A river cuts a valley 12 meters deeper over 3000 years. What is the average erosion rate in meters per year?
- 2 A coastline cliff retreats 2.4 meters in 8 years. If the rate stays constant, how far will it retreat in 25 years?
- 3 Explain why a glacier can carve a U-shaped valley while a river usually cuts a V-shaped valley.