1911 Encyclopædia Britannica/Giant's Kettle

GIANT’S KETTLE, Giant’s Cauldron or Pot-Hole, in physical geography, the name applied to cavities or holes which appear to have been drilled in the surrounding rocks by eddying currents of water bearing stones, gravel and other detrital matter. The size varies from a few inches to several feet in depth and diameter. The commonest occurrence is in regions where glaciers exist or have existed; a famous locality is the Gletscher Garten of Lucerne, where there are 32 giant’s kettles, the largest being 26 ft. wide and 30 ft. deep; they are also common in Germany, Norway and in the United States. It appears that water, produced by the thawing of the ice and snow, forms streams on the surface of the glacier, which, having gathered into their courses a certain amount of morainic débris, are finally cast down a crevasse as a swirling cascade or moulin. The sides of the crevasse are abraded, and a vertical shaft is formed in the ice. The erosion may be continued into the bed of the glacier, and, the ice having left the district, the giant’s kettle so formed is seen as an empty shaft, or as a pipe filled with gravel, sand or boulders. Such cavities and pipes afford valuable evidence as to the former extent of glaciers (see J. Geikie, The Great Ice Age). Similar holes are met with in river beds at the foot of cascades, and under some other circumstances. The term “pot-hole” is also sometimes used synonymously with “swallow-hole” (q.v.).