Lake Miers is covered by a thick ice sheet which is domed over most of its area and thrust into sharp debris-covered ridges around its margin. Ridges result largely from compression generated in the ice raft by freeze and thaw. Apart from a narrow moat in summer the ice round the lake shore is frozen fast to the lake bed. The margin of the floating ice raft is thrust over the fast shore ice to form pressure ridges. In the prevailing aridity the ridges ablate relatively swiftly and an equilibrium is attained between the rates of uplift and downwasting. With continued uplift the infrozen gravels migrate to the surface of the ridges and accumulate there as a residual cover. Because of its low albedo the debris cover causes locally increased insolation, and because it is thin, heat is conducted to the underlying ice and ablation is increased. These active and young moraines are quite different from passive and ancient ice-cored moraines. The latter are preserved only because of a thick and insulating debris cover: the Lake Miers ridges exist despite their thin insolating gravel cover and primarily because they are dynamic.