 The main plateau of the central part of the island, which was once the sea bottom of the ancient Iapetus Ocean, has been heavily eroded by water and ice.Steep, solitary rock knobs, called "tolts" in Newfoundland (elsewhere known as inselbergs or monadnocks), which jut or more above the generally flat terrain are the remnants of a former higher landscape level.Glaciers which helped shape these tolts left other evidence around Newfoundland.