This is one of the most famous images of a nuclear detonation, a shot of the American blast codenamed Dakota, which was part of Operation Redwing, conducted at Bikini Atoll, Marshall Islands, today in 1956. The layered effect you see is sometimes called a Wilson cloud, and consists of water vapor condensed out of the atmosphere by rarefaction, an aftereffect of a shockwave traveling through humid air. In order to perform tests on Bikini Atoll, about 200 Micronesian inhabitants were forced to relocate. They and their descendants hope to return one day, but as of now their home is still too contaminated with radiation.
What goes up must come down—even radiation.