Volcanic Activity on the Patagonian Ice Cap
1960; Wiley; Volume: 126; Issue: 4 Linguagem: Inglês
10.2307/1793373
ISSN1475-4959
Autores Tópico(s)Cryospheric studies and observations
ResumoThe main purpose of my second visit to Patagonia in the summer of 1959-60 was to locate and investigate an active vent, which was believed to exist somewhere on the southern of the two main ice caps. The evidence that there was such a vent had accumulated over very many years. For example, nearly fifty years ago some travellers had described showers of ash falling near the western end of Lago Viedma; deposits of ejecta had been observed on the O'Higgins Glacier, the Chico Glacier and elsewhere in that area; and, according to de Agostini and others, settlers near the shores of Lago O'Higgins* had talked of seeing, on several occasions, great columns of smoke rising from the ice cap to the west. In 1933, a party led by Dr. Reichert reached the ice cap by ascending the O'Hig? gins Glacier from the southernmost branch of Lago O'Higgins. For sixteen days they were confined to their tents on the edge of the plateau by violent storms, and by the time these had abated their supplies were nearly exhausted. However, they pressed on westwards and reached a point near the main divide. Visibility was still bad, but when they were at about their farthest point it cleared for about a quarter of an hour and they saw, close at hand, a volcanic cone, some 3000 metres high, from which clouds of steam were issuing. For some reason Reichert's discovery did not receive the recognition it deserved, and in the subsequent speculation about the existence and whereabouts of the volcano it seems to have been largely ignored. His route to the ice cap had been followed twice, in 1957 and 1958, by parties led by Hugo Corbela, but no fresh evidence had emerged. In 1944-5 the American Air Force made a series of survey flights over the range. Examining the photographs taken on these, Professor Keller of the University of Chile and Dr. L. Lliboutry found what they thought to be an active vent on a large rock outcrop in the accumulation area of the Viedma Glacier. In 1952 observations made by Lliboutry on another flight seemed to confirm this belief, and the outcrop came to be known as Vulcan Viedma. It was not likely, however, that this was the origin of the deposits found in the vicinity of the O'Higgins Glacier; nor could it account for the eruptions seen by settlers on the shores of Lago O'Higgins. Lliboutry, who devoted a section of his book 'Nieves y glaciares de Chile' to a review of the question, was inclined to the opinion that the active vent or vents causing these phenomena were not located on any of the mountains rising above the ice cap, but rather that they were fissure volcanoes which erupted periodically and were covered by snow and ice during their intervening periods of quiescence. He noticed on the American Air Force photographs a number of peculiar markings # The eastern part of this lake, which lies in Argentina, is called Lago San Martin. 26
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