The New Siberian Islands once formed major hills within the Great Arctic Plain that covered the northern part of Late Pleistocene "Beringia" between Siberia and Alaska during the Last Glacial Maximum (Late Weichselian Epoch). These islands represent the remains of about 1.6 million square kilometers of the formerly subaerial Great Arctic Plain that now lies submerged below parts of the Arctic Ocean, East Siberian Sea, and Laptev Sea. At this plain's greatest extent, sea level was 100–120 m below modern sea-level and the coastline lay 700 to 1000 kilometers north of its current position. This plain did not undergo extensive glaciation during the Late Pleistocene or the Last Glacial Maximum because it lay in the rain shadow of the Northern European ice sheet. During the frigid polar climate of the Last Glacial Maximum, 17,000 to 24,000 BC, small passive ice caps formed on the adjacent De Long Islands. Fragments of these ice caps remain on Jeannette, Henrietta, and Bennett Islands. Traces of former small slope and cirque glaciers in the form of buried ground ice deposits are preserved on Zhokhov Island. The sea submerged the Great Arctic Plain (except for the New Siberian and other isolated islands) within a relatively short time span of 7,000 years during the Early–Middle Holocene.