In 1971 US military scientists detonated Cannikin, a five megaton nuclear bomb, beneath the Alaskan island of Amchitka to test the geographical impact of a huge underground nuclear blast. As this video clip shows the explosion caused the ground to rise 20 feet and led to the formation of a new lake.

Amchitka is a volcanic island in the Rat Islands group of the Aleutian Islands in southwest Alaska. It was selected by the US Atomic Energy Commission as the site for underground nuclear tests. Out of three such tests, Cannikin in on November 6, 1971, estimates for the precise yield ranging from 4.4 to 5.2 megatons, or an explosive force equivalent almost 400 times the power of the Hiroshima bomb. The explosion created a new lake, over a mile wide and a seismic shock of 7.0 on the Richter scale, causing rock falls and turf slides of a total of 35,000 square feet (3,300 square m). A number of small tectonic events occurred in the following weeks, some as high as 4.0 on the Richter scale. According to wildlife surveys by the University of Fairbanks, 700 to 2,000 sea otters were killed by overpressures in the Bering Sea as a direct result of the explosion.

The note at YouTube says, “Nearly three hundred deceased rock greenling fish were found offshore, and subsequent catches of rock sole declined substantially. The remains of over 10,000 three-spined sticklebacks and 700 Dolly Varden were found in the island's lakes, streams, and ponds. Perhaps 1,000 sea otters were killed, their skulls fractured by the force of the blast driving their eyeballs through the bones behind their sockets. Harlequin ducks were found with their backs broken and their legs driven into their bodies by the force of the explosion."