The lakes in the McMurdo Dry Valleys have a density gradient which in turn prevents the usual vertical convection seen in other lakes. Consequently the basal layers of the lakes remain stagnant. Crustal gases permeate through the permafrost into the deep layers of the lake where they become trapped, and the hydrostatic pressure increases the solubility of these gases. By sampling these layers it ... is possible to measure the amount of gas percolating through the earth's crust in Antarctica. Samples of basal waters were taken from Lake Fryxell, the east and west lobes of Lake Bonny and from Lake Vanda, using a pressure sampler which enabled the sample to be retrieved without gas loss. Three different samples from the base of each lake were taken including water/gas samples for dissolved gas concentration (N2,O2, CO2, He, Ne, H2 and CH4), and gas samples for isotope gas ratios (C13, He3, He4). The pressure, temperature, pH, H2S concentration, depth and ice cover was measured from each site.