The Southern Patagonian Ice Field ( or ), located at the Southern Patagonic Andes between Chile and Argentina, 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. Geography The Southern Patagonia Ice Field extends from parallels 48° 15′ S to 51° 30′ S for approximately , and has an approximate area of , of which 14,200 km2 belong to Chile and 2,600 km2 belong to Argentina. The ice mass feeds dozens of glaciers in the area, among which are the Upsala (765 km2), Viedma (978 km2) and Perito Moreno (258 km2) in the Los Glaciares National Park in Argentina, and the Pío XI Glacier or Bruggen Glacier (1,265 km2, the largest in area and longest in the southern hemisphere outside of Antarctica), O'Higgins (820 km2), Grey (270 km2) and Tyndall (331 km2) in Chile. The glaciers going to the west flow into the fjords of the Patagonian channels of the Pacific Ocean; those going to the East flow into the Patagonian lakes Viedma and Argentino, and eventually, through the rivers de la Leona and Santa Cruz, to the Atlantic Ocean. An important part of the ice field is protected under different national parks, such as the Bernardo O'Higgins and Torres del Paine in Chile, and the aforementioned Los Glaciares in Argentina. There are two known volcanoes under the ice field; Lautaro and Viedma. Due to their inaccessibility they are among the least researched volcanoes in Chile and Argentina. History Exploration Thorough explorations include the expeditions of Federico Reichert (1913–1914), Alberto de Agostini (1931), and Harold William Tilman and Jorge Quinteros (1955–1956); as well as Eric Shipton (1960–61). The first (North-South) crossing of the field was accomplished in 1998 by Pablo Besser, Mauricio Rojas, José Montt and Rodrigo Fica. Nevertheless, some areas of the field remain largely unexplored From the air, initial exploration was conducted in 1928–29 by Gunther Plüschow after whom a glacier is named. It was further studied in 1943 by aerial photographs made by the United States Air Force on request of the Chilean government. Borderline Fifty kilometers of the Chile–Argentina border, between Mount Fitz Roy and Cerro Murallón, remain undefined on the ice field. This Southern Patagonian Ice Field section of the border is the last remaining border