The Effect of Freezing & Thawing on Rock

Weathering

• Weathering is a process by which rocks are broken up into small bits by forces such as the air and water. The Southern Kings Consolidated School demonstrates how weathering processes can be either mechanical or chemical. Mechanical weathering includes the action of freezing and thawing, in addition to the action of sudden changes in temperature, the impact of running water, and the splitting effect of plant roots that can grow between cracks in the rock.

Freeze-Thaw Weathering

• Water from melting snow or rainfall infiltrates into cracks in rocks. If the air temperature drops below zero degrees Fahrenheit, the water in these cracks will freeze; this often occurs during the night. When the water in the cracks freezes, it expands by 9 to 10 percent, exerting pressure on the rock, according to BBC Bitesize. This action can widen the cracks in the rock, and when the temperature rises above freezing, the ice thaws, allowing the water to seep further into the cracks. As this process of freezing and thawing happens repeatedly, the rock begins to weaken and eventually breaks apart into angular fragments. This process of freezing and thawing is also known as frost shattering, and is most effective in areas where the temperature fluctuates around zero degrees Fahrenheit, according to BBC Bitesize.

Impacts of Freeze-Thaw

• Freeze-thaw can help to shape mountains and areas of exposed rock that experience fluctuations in temperature around zero degrees Fahrenheit. In addition, the Southern Kings Consolidated School explains how freeze-thaw weathering can damage roads, resulting in the need for constant repair. The other effect of freeze-thaw weathering on rock is the accumulation of loose material that breaks off, called scree, as explained on the Bodmin College website. This loose rock can pose a hazard, as it can accumulate and form debris flows, which can block mountain roads or damage infrastructure. However, much of this loose rock is transported away by rivers, which erode the landscape.

Role of Erosion

• Erosion is the process in which the weathered rocks are removed by the action of wind, water, ice or gravity, according to the Bodmin College website. Erosion further shapes the landscape and breaks down rocks.