Geologists survey the crater rim of Mt. Erebus, the most active volcano in Antarctica. The flanks were littered with volcanic bombs from an eruption a few hours earlier, after a two-day wind and snow storm. Temperatures here were around -30°C and windy, which makes for conditions similar to those encountered on the world's highest peaks. Although Erebus is only 3794M high, the effective air density is much lower than at similar altitudes in temperate regions, due to the effect of the spin of the earth piling up more atmosphere near the equator than at the poles. This makes Erebus have air densities of peaks of 4,350 M in the tropics. Seen here are geologists Bill McIntosh, Alexander Gerst, and writer Lars Abromeit.