National Geographic : 1967 Feb
C~n wNw xo ^N ON Melting out its own grave, a research hut sinks into Lowell Glacier. A helicopter evac uates costly equipment. This outpost served as a scientific base camp of the National Geographic Society-sponsored expedition that first scaled 13,905-foot Mount Kennedy, 20 miles away at far right. Winter winds exceeding 100 miles an hour lash this wild region of heavy, glacier-nourishing snows northward shifts of continental storm tracks producing lighter snows in most southern states (page 208). But changing storm tracks cannot begin to explain what causes certain glaciers to go on rampages, surging many feet a day. Since 1958 we have observed more than a dozen spectacular advances of this type. Glaciolo gists Tarr and Martin half a century ago ob served similar advances and theorized that they might have been caused by avalanches set off by the 1899 earthquake. To this day, some think this a reasonable explanation. Alaska indeed has one of the most quake-sensitive coasts on earth. Glaciers "Gallop" for Complex Reasons But I am more cautious; many glaciers surge without the weight of avalanches being dumped on them. Quake-caused slides may in certain cases, however, be a factor. Since the Alaska earthquake of March 27, 1964, we have recorded at least 500 ava lanches that thundered down on glaciers be cause of that catastrophic event.* Most were small and had little effect on ice movements. In the southern Chugachs, however, half a mountain collapsed on Sherman Glacier, cov ering ten square miles. Not far away, a com parable slide spilled abillion tons of pulverized rock onto Schwan Glacier. In these two cases alone, the area involved corresponds to about a fourth of Washington, D. C. I expect that several glaciers like the Sher man and Schwan, now slowly thinning at the fronts, will shoot ahead for a time because of the weight of earthquake avalanches. Others already race forward: the Tyeen, Carroll, several tributaries of the Grand Pa cific on Glacier Bay, the Lucia, Turner, Dusty, and Steele in the St. Elias district. The mar gins of the upper Dusty, which rises just east of the Mount Hubbard-Mount Kennedy mas sif, look as if a giant saw had ripped them for miles (pages 214-15). Provisionally, it appears that a spectacular advance like the Dusty's is tripped by a com bination of heavy snowfalls at high levels and 216 < ^ w 6 70~ the sudden weight of massive avalanches. The possibility exists, too, that a "fatigue factor" within the ice itself causes these surges. Nearby Steele Glacier, its terminus lately stagnant, is now stampeding two feet an hour along its margins, and probably several times faster in midstream. Our aerial photographs of this phenomenon show a 19-mile-long no man's land of tottering ice pinnacles. Before our visit to the glacier, Dr. Walter A. Wood, director of the Icefield Ranges Research Project in the St. Elias Mountains, *Dr. Miller described "Our Restless Earth" as back ground to quake articles by William P. E. Graves and Mrs. Lowell Thomas, Jr., in the July, 1964, GEOGRAPHIC.