Geological records show the presence of the ice sheet since the
Eocene Epoch, about 56 million to 33.9 million years ago. Deep-sea sediment cores from northeast Greenland, the Fram Strait, and the south of Greenland suggest that the Greenland Ice Sheet has continuously existed since 18 million years ago. More-numerous glaciation records are seen after about 14 million years ago, during the Middle
Miocene. A warm interval occurred about 2.4 million years ago, as evidenced by a unit, 328 feet (100 metres) thick, of sand, silt, and clay in northern Greenland. The period from 424,000 to 374,000 years ago is considered to be the best
analog to the current global climate, and during this phase Greenland is thought to have been almost ice-free.