Signs Of Volcanism Below Scott Base

Press, Volume C, Issue 29695, 13 December 1961, Page 7

Signs Of Volcanism Below Scott Base

The surface temperature at Scott Base, Antarctica, may be cool, but below ground things are decidedly warm, according to Dr. B. I. Robertson, director of the Geophysics Division of the Department of Scientific and Industrial Research. The heat flow from the underlying strata seems to be 20 to 30 times the normal for regions not in a thermal area, and probably indicates activity connected with the volcanism of Ross Island, Dr. Robertson said yesterday.

"I don’t think the temperature gradient in the ground under the base is dangerously abnormal—there is no reason to expect that the place will blow up tomorrow.” said Dr. Robertson. “But we would do well to go down to. say, 100 ft and see if the trend continues. The heat flow is at least 10 times greater than anything we have in New Zealand outside the immediate thermal areas ”

Dr. Robertson’s findings are based on readings from a 15ft borehole from which temperature readings were taken regularly at various dep'hs for a whole year. Under normal conditions, the mean annual temperature underground increases only very slowly with depth—about Ideg Centigrade in LOQft. At Scott, however, the increase is several degrees in the 15ft over which readings were taken. The temperatures were measured by thermocouples at the surface and depths of Ift, 2ft, 3ft, sft 7ft, 10ft, and 15ft. “It is not surprising that there should be volcanism in the Scott Base area.” Dr. Robertson added. ‘‘After all. the base sits on the flanks of Crater hill and Ross Island itself is not much more than a group of volcanoes. These measurements merely show that the area is not dead from a volcanic point of view.”

Alternative suppositions were that the climate of former years might have been warmer than now. or that the heat was produced by radioactivity But an examination of climatic records had shown that the temperature increase with depth was far greater than could be explained by climatic effects, and the amount of radioactivity necessary to produce the heat was also quite out of the question. A borehole to 100 ft should yield immediate information on the heat flux at such a depth, because seasonal fluctuations in temperature became smaller and smaller as one descended, Dr. Robertson added. Another anomaly at Scott

Base, shared by the McMurdo Base and Hallett station, was a ’‘fantastic" change in electrical conductivity of the ground or surface ice with temperature changes. A fall in temperature by about 3 sdeg Centigrade the conductivity down to half its previous value, said Dr. Robertson Samples of basaltic scoria penetrated by ice had been brought out from Scott Base and investigated by the Dominion Laboratory of the DSJ.R, which had confirmed that the changes in conductivity were of this order. Ice from in front of the Ross Ice Shelf had also been tested and the same phenomenon found in each. Ute conductivity changes would make earthing of equipment difficult and could upset experiments, such as earth current measurements, where use was made of electrodes sunk into the ground or ice.