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T322 Atlas p. 33&42 Southern Andes/Chilean Agriculture, Chile, Argentina Land use, glaciers Significance: The lower spine of the Andes is one of the least explored mountain regions of the world. Lying on the edge of the subduction zone where the oceanic crust of the Pacific Plate is forced under the continental crust of the South American Plate, the folds and overthrust belts of the Andes have experienced dramatic uplift in recent geological time. Along the coastline, terraces preserving historical shorelines are now up to a 100 m above sea level, while Pleistocene terraces may be found on mountainsides more than a 1000 m high. In addition to the rapid regional uplift, volcanic activity is recorded by many young volcanoes and calderas. Several calderas have been recently discovered in Bolivia and northwestern Argentina by the analysis of LANDSAT imagery and Shuttle photographs. Volcanologists are now attempting surveys of the Andes to locate other calderas of the kind responsible for eruptions producing more than 1000 km3 of ejecta. Glaciers in these high mountains are dynamic and sometimes have a major impact on the population, as seen in the recent flood threat caused by the glacier Grand del Nevado--northeast of the Santiago in the Argentinean Andes. This glacier has surged across a river, creating a lake of considerable volume. Space photographs offer a good opportunity to map and monitor glaciers and their movement. The coastal plain of Chile from just north of Santiago southward to near Valdivia is the heartland of Chilean agriculture. The region known as the Chile Mediterranean Belt is undergoing dramatic land use changes. Since access to the country is very limited, photographs along this belt will allow scientists to analyze the changes and erosional characteristics that are occurring. Physical Characteristics: Local ice sheets covered much of the Andes during the last ice age, resulting in the formation of many steep-sided mountain cirques, glacial U-valleys and large river channels now occupied by much smaller streams. Just east of the Gulf of Penas, near the volcanic peak of Son Valenlin, a remnant glacier continues to cover approximately 23,000 km2. The long, narrow Lake Buenos Aires just to the east of this region is fed by the melt water of this gigantic glacier. Active volcanoes are numerous in the region. The highest peak in the Western Hemisphere, Aconcagua, situated some 110 km northeast of Santiago, is a steep glacier-carved barren crested volcanic mountain. Several jagged peals in this region reach heights of 6100 m and more. The density of vegetation changes dramatically across the site region. The northern area is an almost barren desert while the southern area, with its beautiful and spectacular fjord coastline, supports forests of conifer, primitive massive oak, and beech trees. The Chilean agriculture region lies in what is called the Central Valley (30°-40° S) and is the most densely populated, economically active, part of Chile. In the northern Central Valley, irrigation is needed to support a great variety of crops including wheat, barley, potatoes, fruits and grapes. To the south where rainfall is more evenly distributed year around, irrigation is unnecessary. Potatoes and sugar beets are the main crops; large pastures support dairy cattle. Observation Techniques: Stereoscopic image series with 60% frame overlap using the 250-mm lens will provide the most effective coverage. 250 mm coverage of the ends of glaciers is desired, especially if it can be done on a few successive days throughout flight. Use the 100 mm lens to take low-oblique and near-vertical views of the Central Valley especially showing the penetration of agricultural practices up the slopes of the mountains and the snow level on the high peaks. Simultaneous 100 mm and 250 mm lens views will be of considerable value since little or no photography exists over this fascinating region of the world. CIR film use is encouraged. Center point: 40° S, 72° W 181
