Freeze-thaw action is a key process that shapes periglacial landscapes by causing the physical weathering and erosion of rocks and soil.

In periglacial environments—regions adjacent to glaciers or characterized by cold climates—the freeze-thaw cycle is a dominant mechanism that profoundly impacts the landscape. This process involves the repeated freezing and thawing of water trapped within cracks and pores in rocks and soil. When water freezes, it expands by approximately $9\%$, which exerts significant pressure on the surrounding material. This pressure can surpass the strength of the rock or soil, leading to fractures and disintegration.

The freeze-thaw cycle initiates when temperatures fall below $0^\circ C$ (32°F), causing water within the rock or soil to freeze and expand. This expansion generates stress within the material, resulting in the formation of cracks and fissures. As temperatures rise above freezing, the ice melts and the water infiltrates deeper into these cracks. When temperatures drop again, the water freezes, causing further expansion and deepening of the cracks. In periglacial environments, this cycle of freezing and thawing can occur multiple times within a single day, leading to substantial physical weathering and erosion.

Over time, the continuous freeze-thaw action can give rise to distinctive periglacial features. For example, frost heaving—the upward movement of the ground caused by the freezing of water in the soil—can create patterned ground formations such as sorted circles and stone stripes. Additionally, freeze-thaw processes can lead to the development of solifluction lobes and sheets, which are slow, downslope movements of water-saturated soil and rock debris.

Furthermore, freeze-thaw action plays a role in the formation of permafrost, a layer of soil or rock that remains at or below freezing for at least two consecutive years. The presence of permafrost can further influence the periglacial landscape by affecting water movement and ground stability.

In summary, freeze-thaw action is essential in shaping periglacial landscapes. Through processes of physical weathering and erosion, it contributes to the formation of unique periglacial features and plays a significant role in the development of permafrost.