The Dry Valleys comprise an ice-free part of the Transantarctic Mountains in Antarctica, bounded by the East Antarctic Ice Sheet on the landward side and a coastal ice dome at the coast. Weathering rates are among the lowest on Earth and reflect the persistent hyper-arid, cold polar desert climate. Some buried ice has survived for over 8 million years. The main escarpments and valleys were created on a passive continental margin as Antarctica split from Australia some 55 million years ago. Ice sheet glaciations covered the area some 14 million years ago, deepening some valleys. Sub-glacial lake outbursts, possibly from Lake Vostok, cut the spectacular Labyrinth, a network of vast channels. During Pleistocene glacial periods grounded ice in the Ross Sea dammed large lakes in the lower reaches of the valleys.