Cryogenic grooves on a granite nunatak, Northern Victoria Land, Antarctica

Numerous grooves, or furrows, occur near the summit of a biotite-monzogranite nunatak in the Northern Foothills region, northern Victoria Land, Antarctica. The grooves are developed on steeply inclined (>35°) bedrock surfaces and are generally straight, typically 10-30 cm deep, 20-80 cm wide, and up to 10 m in length. Although resistant xenoliths in the monzogranite influence some of the grooves, the majority possess no structural control. The ridges that separate the grooves are often sharp. Many grooves join and bifurcate, always in an upslope direction. Some meander and possess asymmetrical cross profiles. The grooves are provisionally interpreted as cryogenic micro-erosional features. They are formed by meltwater associated with the repeated melting and refreezing of snow on steeply inclined rock surfaces exposed to direct solar radiation in late spring and early summer when air temperatures remain well below zero.