Thule Island is approximately triangular in shape and in area with a long, panhandle-like peninsula, , extending to the southeast. Steep slopes ascend to a summit caldera with the peak of Mount Larsen at above sea level. Mount Larsen is named after the Antarctic explorer and whaler Carl Anton Larsen. Off the southeastern tip lies the small islet of Twitcher Rock, the southernmost land on Earth except for Antarctica and offshore islands considered part of Antarctica.