"It is a fine case of a well-known phenomenon called a glacial pothole."
Geologist J.C. Branner, 1884
About 20,000 years ago, a powerful, whirling mixture of frigid glacial water, sand and stones wore away solid rock, forming this pothole.
At the pothole's discovery, geologists proposed that it was carved by a waterfall falling through a crevasse (crack) in the glacier. Many modern geologists still support this original theory.
A recent addition to this hypothesis places a lake on top of the glacier as a long-term water supply for the waterfall.
Other geologists propose that there was no waterfall. They argue that a large, fast-moving stream under the glacier supplied the swirling water that created the pothole.
Melted ice carrying abrasive sand and stones created this glacial pothole.
Comparisons confirm that this is a world-class glacial pothole. From bottom to top it measures 38 feet. At one place it is 42 by 24 feet in diameter.