Periglacial
Stone rings, pingoes, and rock glaciers and other periglacial activity became more common during ice ages.
Periglacial activity is a geomorphic process that occurs due to periodical defrosting of snow in regions of permafrost (frozen ground), the runoff which becomes frozen again in ice wedges and other structures. During periglacial activity, there is a regular fluctuation of air temperature across zero degree Celsius, and the process influences the landscape in a significant way.