Marie Byrd Land (MBL, longitude 100-150° W) is one of the least accessible and least frequently visited regions in Antarctica (Fig. 1, 2). It was discovered from the air and claimed for the United States by Richard E. Byrd in 1929, and named for his wife. Much of this region was then explored during the second Byrd expedition (1934-35) by two tractor parties, one sled party led by Paul Siple and four exploratory flights. The US Antarctic Service Expedition explored the region in 1939-41, as well as the Executive Committee Range Traverse in 1959, with oversnow tracked vehicles from Byrd Station. More recently, US scientists mapped, sampled and collected GPS data, as well as drilled snow and ice cores on the summit of some of the volcanoes.