around the caldera, especially in the north-northwestern and south-southeastern sectors, while warm ground is more restricted. In the northern sector of the volcano, ice towers and bare ground form a southeast–northwest trending lineament. Ice towers form when fumarolic gases freeze in the cold Antarctic air. Glacial caves form when geothermal heat melts ice, leaving cavities. Some of these caves are in the summit caldera and reach lengths of several hundred metres, with ceilings reaching height. Several caves have been accessed through ice towers or through gaps where the ice surrounding the cave rests on rock, and one ice cave ("Aurora Ice Cave") was mapped in 2016. The caves and ice towers release water-vapour-rich warm air. Fumarole temperatures can reach , contrasting with the cold air. Fumaroles release gases containing excesses of volcanic carbon dioxide and methane. Hydrogen sulfide gas has been detected too, but only at low concentrations which do not prevent the development of vegetation. Yellow deposits have been identified as sulfur. The geothermal manifestations appear to be powered mainly by steam, as there is no evidence of geothermal landforms related to liquid water flow and heat conduction is not effective enough at most sites. It is possible that underground liquid water reservoirs form in some areas, however. The steam is produced by the melting and evaporation of snow and ice, and is then channelled through rocks to the vents. Atmospheric air likely circulates underground and is heated, eventually exiting in ice towers. An early theory that the ice towers formed on top of a cooling lava flow is considered improbable given the long duration of fumarolic activity; a lava-heated system would have cooled down by now. Climate There are no detailed meteorological records of the summit region. Winds blow mostly from the west and more rarely from the northwest. Catabatic winds blow from the Priestly and Reeves valleys. Precipitation is scarce. During winter, polar night lasts about three months. Temperatures in the summit region have been variously reported to either not exceed or to range between . Seasonal temperature variation is high and reaches . During the Last Glacial Maximum (LGM), a marine ice sheet occupied Terra Nova Bay. The "Terra Nova Drift" was deposited between 25,000 and 7,000 years ago and is overlaid by later moraines from retreating ice during the post-LGM period. During the late Holocene after 5,000 years before present, glaciers advanced again as part