How does freeze-thaw activity shape tundra landscapes?

Freeze-thaw activity is a primary force in shaping tundra landscapes, driven by the alternating freezing and thawing of ground moisture within the active soil layer. This process creates several distinct geological features:12

• Patterned Ground: The differential movement of soil, stone, and rock results in surface patterns such as polygons, stone circles, and stripes. These forms emerge as freezing and thawing cause frost heaving and the sorting of debris.12
• Solifluction: Because permafrost is impermeable to water, the saturated active layer of soil can slide downhill over the frozen ground. This process, known as solifluction, grades slopes into long, smooth profiles and can cause rock slabs to stand on end.12
• Pingos: During winter, water in the soil may freeze into ice lenses, which can push the ground upward to form large, hilly structures called pingos.12
• Felsenmeer: Frost action breaks up exposed bedrock, creating mantles of angular, shattered boulders known as Felsenmeer, which can reach significant depths on uplands.2

These cycles are most intense in spring and fall, fundamentally dictating the physical structure of both Arctic and alpine tundra environments.1