The Patagonian Ice Sheet was a large elongated and narrow ice sheet that covered all of Chile south of approximately present-day Puerto Montt during the Llanquihue glaciation. Some maps have the Patagonian Ice Sheet connected to the icecaps of the Altiplano by continuous glaciers all the way through the Andes.
The ice sheet extended beyond the crest of the Andes into Argentina, but because of the dryness of the climate it did not reach beyond present-day lakes such as the Yagagtoo, Musters, and Colhue Huapi. At its peak (about 18,000-17,500 years ago), the Patagonian Ice Sheet covered about 480,000 km² of land with an estimated ice-volume of more than 500,000 km³, of which about 4% remains glaciated today in two separated portions known as the Northern and Southern Patagonian Ice Fields. The ice-volume reduction contributed to a global sea-level rise of about 1.2 meters. However, during the first glacial period at the beginning of the Pleistocene ice extended to the present-day Argentine coast. With each successive glaciation it is known that the ice has stopped further and further to the west, with aridity always serving as the decisive factor halting glacier spread: it is believed that the east-west precipitation gradients during glacial periods were even steeper than the extremely steep ones of present-day Patagonia.
The Southern Patagonian Ice Field (Spanish: Hielos Continentales or Campo de Hielo Sur), located at the Southern Patagonic Andes between Argentina and Chile, is the world's second largest contiguous extrapolar ice field. It is the bigger of two remnant parts of the Patagonian Ice Sheet, which covered all of southern Chile during the Last glacial period, locally called the Llanquihue glaciation.