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How does freeze-thaw weathering break up rocks?

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Quick Answer

Freeze-thaw weathering is a form of physical or mechanical weathering that induces stress on rocks when water repeatedly seeps into cracks, freezes and expands, eventually causing the rock to break apart. This type of weathering is largely driven by the intensity and frequency of freeze-thaw cycles and the structural properties of the rocks subject to weathering.

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Full Answer

When water from melting ice and snow or rainfall gets trapped within the joint or crack of a rock, and the surrounding air temperature drops to below 32 degrees Fahrenheit, the water freezes and expands by 9 to 10 percent, exerting pressure on the rock. Once the surrounding air temperature rises above freezing, the ice in the crack melts. If this continues, the rock eventually weakens and shatters into fragments. These fragments fall to the foot of the slope as scree. Freeze-thaw weathering mostly occurs in areas where temperatures fluctuate around 32 degrees.

Physical weathering may also be caused by rampant temperature changes and the effects of waves, rain and wind. It typically takes place over a long period of time. Other forms of weathering include: biological weathering, which occurs when plants and animals wear away rocks, and chemical weathering, which is induced by chemical, like the carbon dioxide present in rainwater.

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