The De Long Islands (; ) are an uninhabited archipelago often included as part of the New Siberian Islands, lying north east of Novaya Sibir. Geography This archipelago consists of Jeannette Island, Henrietta Island, Bennett Island, Vilkitsky Island and Zhokhov Island. These five islands have a total area of 228 km². Bennett Island is the largest island and it has also the archipelago's highest point at 426 m. These islands lie around 77°N, are partially covered by glaciers, and rise to peaks. In 1996, the total area of these islands covered by ice caps and glaciers was 80.6 km². This island group belongs to the Sakha (Yakutia) Republic administrative division of Russia. Geology Early Paleozoic, Middle Paleozoic, Cretaceous, and Neogene rocks have been mapped within the De Long Islands. The Early Paleozoic rocks are Cambrian and Ordovician sedimentary rocks interbedded with minor amounts of limestone. The Middle Paleozoic rocks consist of predominately folded and faulted basaltic, andesitic, and dioritic volcanoclastics, tuffs, lavas, dikes, and sills. Cretaceous rocks are composed of basalts and interbedded argillites, sandstones and minor coals. The youngest rocks exposed within the De Long Islands are Neogene basaltic volcanic rocks. Quaternary geology The De Long Islands were once major hills within the Great Arctic Plain that once formed the northern part of Late Pleistocene “Beringia” between Siberia and Alaska during the Last Glacial Maximum (Late Weichselian Epoch). These islands are what remains of about of the formally subaerial Great Arctic Plain that now lies submerged below the Arctic Ocean and East Siberian Sea. At this plain's greatest extent during the Last Glacial Maximum, sea level was 100–120 m below modern sea level and the coastline was located north of its current position. This plain was neither extensively glaciated during the Late Pleistocene nor during the Last Glacial Maximum because it lay in the rain shadow of the Northern European ice sheet. The Great Arctic Plain was submerged, except for the New Siberian and other isolated islands, within a relatively short time span of 7,000 years during the Early-Middle Holocene. During the extremely frigid polar climate of the Last Glacial Maximum (Late Weichselian Epoch), 17,000 to 24,000 BP, small passive ice caps did form on the De Long Islands. Fragments of these ice caps are preserved on Jeannette, Henrietta, and Bennett Islands. Traces of former Late Weichselian slope and cirque glaciers in the form of buried ground ice deposits