Geology
The valleys cut through the Beacon Supergroup, as well as older granites and gneisses of the Ross Orogeny. Tills, deposited directly from ice, dot this bedrock landscape. These tills are relatively thin and patchy, and differ markedly from the extensive, mud-rich tills of the Laurentide ice sheet in the Northern Hemisphere. One reason for the difference is that most of the tills in the Dry Valleys were deposited from cold-based ice (ice with basal temperatures below 0 °C (32 °F)), whereas the Laurentide ice sheet was largely wet-based, with significant melting at the base and at the glacier surface.
Read more about this topic: McMurdo Dry Valleys