This chapter is the sixth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, a series of 11 chapters. In each chapter, remotely sensed images, primarily from the Landsat 1, 2, and 3 series of spacecraft, are used to study the glacierized regions of our planet and to monitor glacier changes. Landsat images, acquired primarily during the middle to late 1970's, were used by an international team of glaciologists and other scientists to study various geographic regions or to discuss glaciological topics. In each geographic region, the present areal distribution of glaciers is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of glacier ice on our planet during the 1970's as part of a growing international scientific effort to measure global environmental change on the Earth's surface.

The Andes Mountains of South America, from the Sierra Nevada de Mérida, Venezuela, to Tierra del Fuego, Chile and Argentina, are glacierized to a lesser or greater extent depending on latitude, altitude, and annual precipitation. The largest area and volume of glacier ice, including two large ice fields, each with numerous outlet glaciers, occurs in the Patagonian Andes, southern South America. Landsat images are particularly valuable for monitoring fluctuations of large glaciers, especially outlet glaciers from ice fields and for delineating the areal distribution of large glaciers.

Venezuela has five cirque glaciers with a total area of 2 km2. A rapid loss of glacier ice has taken place during the last century, a process that has accelerated since 1972.

Colombia has many small glaciers with a total area of 104 km2 on six peaks. Its largest glacier (<20 km2) is an ice cap on the active Nevado del Ruiz volcano; in November 1985, an explosive eruption melted part of the summit ice cap, which, when combined with heavy precipitation, generated lahars that killed more than 23,000 people, more than 20,000 in the town of Armero. A consistent and progressive loss of glacier ice and snowpack has been noted since the late 1800's, and many glaciers have completely disappeared during the 20th century.

Ecuador has more than 100 small ice caps, outlet glaciers, ice fields, and mountain glaciers with a total area of about 97 km2. Since the 1800's, the glacier area has undergone a significant continuing reduction.

Perú has a total glacier-covered area of 2,600 km2 on 20 distinct cordilleras. The glacierized cordilleras are important sources of water and as locations of glacier-related avalanches and floods that have destroyed towns and killed tens of thousands of inhabitants.

Bolivia has a total glacier-covered area of more than 560 km2. A few small summit ice caps, outlet and crater glaciers (~10 km2) are located on extinct volcanoes of the Cordillera Occidental in northern Bolivia. Ice caps, valley glaciers, and mountain glaciers (550 km2) are located on the highest peaks of the Cordillera Oriental.

Numerous glaciers in Chile and Argentina occur along the more than 4,000-km length of the Andes Mountains, from very small snow patches and glacierets of the Desert Andes and the 2,200 km2 of glaciers in the Central Andes to the large ice fields and outlet glaciers of Patagonia. The Southern Patagonian Ice Field (~13,000 km2) is the largest glacier outside Antarctica in the Southern Hemisphere. The Northern Patagonian Ice Field (~4,200 km2) and the glacierized Cordillera Darwin in Tierra del Fuego (~2,300 km2) also contain a substantial volume of glacier ice.

Richard S. Williams, Jr.
Jane G. Ferrigno

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