At 11:00 a.m. Alaska Standard Time, the Aleutian Island of Amchitka ceased to be a landmass and became a geological instrument. The Atomic Energy Commission detonated a five-megaton thermonuclear device, codenamed Cannikin, 5,875 feet below its surface. The shockwave, equivalent to a magnitude 7.0 earthquake, permanently raised the island’s surface by twenty feet. It was the largest underground test ever conducted by the United States.
The stated purpose was to validate the warhead design for the Spartan anti-ballistic missile. The test occurred in a region of intense seismic activity, a fact that troubled geologists. Officials claimed the risk of triggering a tsunami or releasing radiation was minimal. They were correct about the tsunami. The blast did, however, create a subsidence crater a mile wide and cause a series of aftershocks. The environmental consequences for the delicate island ecosystem, a refuge for sea otters and bald eagles, were immediate and poorly documented.
Cannikin’s true legacy was not military but activist. The test galvanized a fledgling group called the Don’t Make a Wave Committee, formed to protest earlier tests on Amchitka. In 1971, they chartered a fishing boat named *Phyllis Cormack* to sail into the test zone. Renamed *Greenpeace* for the journey, the boat was intercepted by the U.S. Coast Guard. The mission failed to halt the blast, but the publicity succeeded. The committee formally adopted the name Greenpeace. A single act of geopolitical force birthed a permanent fixture of global environmental watchdogging.