The pre-glacial landscape of Antarctica

The geomorphology of the hidden subglacial landscape of Antarctica is relevant to our understanding of the stability of the Antarctic Ice Sheet and also to that of global interactions between plate tectonics and surface processes. We believe that geomorphology has much to contribute, but that the lack of coherent hypotheses about the origins of the subglacial landscape is holding back understanding. This paper approaches the problem by using southern hemisphere land masses in Africa and Madagascar as analogues. We find that the Antarctic landscape evolved in a similar way to passive margin evolution in southern Africa. Rifting associated with the breakup of Gondwana changed river base levels and caused rapid erosion on the flanks of rifts and was accompanied by the uplift of rift-margin mountains. Rift-margin plains, often coastal or extending inland along large rivers, are backed by an escarpment, while low-gradient continental river basins characterised the interior of Antarctica. In East Antarctica ice has removed pre-existing regolith from lowlands and excavated 2–3 km troughs below sea level along the course of major trunk rivers. The micro-continents of West Antarctica are comparable to Madagascar and apparently share a similar topography with coastal plains, backing escarpments and interior plateaux.