Northern Patagonian Ice Field

The Northern Patagonian Ice Field, located in the Patagonia region of southern Chile, is the smaller of two remnant parts in which the Patagonian Ice Sheet in the Andes Mountains of lower South America can be divided. It is wholly contained within the boundaries of Laguna San Rafael National Park.

The two lobes of the Patagonian ice fields, north and south, are what's left of a much more expansive ice sheet that reached its maximum size about 18,000 years ago. As a result, the modern ice fields are just a fraction of their previous size, though they remain the southern hemisphere's largest expanse of ice outside of Antarctica.

The Northern Patagonian Ice Field is a vestige of the Patagonian Ice Sheet. This extensive ice sheet covered all of Chilean Patagonia and the westernmost parts of Argentine Patagonia during the Quaternary glaciations.

Today, with its glaciers largely in retreat and only an area of 4,200 sq km (1,600 sq mi), the Northern Patagonian Ice Field is still the second-largest continuous mass of ice outside the polar regions. Survival is based on its elevation (1,100 to 1,500 m (3,600 to 4,900 ft)), favorable terrain and a cool, moist marine climate.

While the northern ice field is smaller than its southern counterpart, it still has 30 significant glaciers along its perimeter. Ice creeps downslope through mountain valleys and exits the so-called "outlet glaciers." Many come to an abrupt end on land, while others terminate in water.

The water-terminating glaciers San Rafael and San Quintín are the Northern Patagonian Ice Field's largest and nearly reach sea level to the west at the Pacific Ocean. Smaller exit glaciers, like San Valentín and Nef, feed numerous rivers and glacially carved lakes to the east.

San Rafael Glacier starts near the western flank of Monte San Valentin, the tallest summit in Patagonia, and drains westward into Laguna San Rafael. A ridge of debris rings the lagoon, called a moraine, shoveled into place by the glacier in the past when it was much larger. It still actively sheds icebergs from its front in a process known as calving. San Rafael is one of the most actively calving glaciers in the world.

San Rafael's "twin" is the San Quintín glacier immediately to the southwest. This glacier currently ends in a piedmont lobe and illustrates Laguna San Rafael's appearance before it receded. Until 1991, the glacier terminated on land, but with the glacier's retreat, the basin filled in with water to form a proglacial lake.

_{NASA satellite photo of the North Patagonia Ice Field}