The Cactus test took place May 6, 1958 at approximately 0615. An land-surface type shot was detonated on a platform at the northern tip of Runit, Enewetak in the second of the 35 tests for Operation Hardtack I.The initial cloud from the explosion reached as high as within the first ten minutes, and settled at around by 20 minutes after detonation. The nuclear fallout prediction map proved to be accurate in determining the span and the intensity of the resultant fallout.Measured peak intensity of fallout reached at hour three directly above blast site on the North end of the Atoll. At mid-island the radiation was measured to be . The southern tip received a very small amount of radiation, due to the easterly winds.
