Amchitka is a volcanic, tectonically unstable island in the Rat Islands group of the Aleutian Islands in southwest Alaska.
Military - Historic - Closed Facility, Military - R&D
Amchitka was selected by the United States Atomic Energy Commission to be the site for underground detonations of nuclear weapons. Three such tests were carried out: Long Shot, an 80 kiloton blast in 1965; Milrow, a 1 megaton blast in 1969; and Cannikin in 1971 – at "under 5 megatons", the largest underground test ever conducted by the United States.
The SE end is in much better resolution close up.