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Geology LibreTexts

9.2: Weathering Processes

Weathering is the process by which surface and subsurface rocks disintegrate, dissolve, or are broken down. Rocks at or near the earth's surface are exposed to physical and chemical weathering processes. Weathering is known as an exogenic process because it (like all exogenic systems) is powered by insolation, which drives all systems above the surface of the earth, including the atmosphere, weather, and ice which are also influenced by the earth's gravity.

Soil is formed by weathering-Define the following two words and write a brief description of how soil is formed:

  • bedrock
  • sediment
  • Soil is formed when...

Physical Weathering takes place when rock is broken, but no chemical changes take place. Water is a major cause of physical weathering. Recall from lecture 5 that water actually expands when it becomes solid (freezes). Can you recall the four types of physical weathering?

Chemical Weathering takes place when the air or water interacts with the crystals in a rock to change their chemical composition. This can take the form of oxidation (by the air) or dissolving (by water and other chemicals in the water such as sulfuric acid from acid rain).

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