Project Cannikin

This is detonated at least 6000 feet into the ground (roughly 2000 meters).

"This footage is from Project Cannikin, which was merely a proof-test for the 5 megaton warhead to be used on the Spartan missile system. Researchers were fearful of such a large device being detonated underground, so the testing was moved to way out in the middle of nowhere on the Amchitka penninsula in Alaska.

The effect on the ground was necessary, and predicted, to see its pulse effect."

"The blast registered a 7.0 on the Richter scale and caused a subsidence crater over a mile wide and 60 feet deep, which filled with water and became the largest lake on the island. Rockfalls, containing over 46,000 square yards of material, smothered intertidal marine life. 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."