Nagasaki: Life After Nuclear War by Susan Southard:
The nuclear test took place just before dawn on March 1, 1954, at the United States’ Pacific Proving Grounds, located at the northern edge of the Marshall Islands, a 750,000-square-mile region in the South Pacific dotted with more than 1,200 tiny islands with a total combined landmass of only 70 square miles. The hydrogen bomb exploded on Bikini Atoll, a narrow, 3-square-mile crescent-shaped series of minute coral islands around a large lagoon. The bomb’s force equaled fifteen million tons of TNT—almost seven hundred times more powerful than the bomb dropped on Nagasaki.
The blast instantly gouged a crater in the island a mile wide and two hundred feet deep. All vegetation on the atoll was destroyed. Within seconds, a fireball nearly 3 miles across rose 8 miles above the ocean, filled with tons of extracted sand, crushed coral, and water. Within ten minutes, the mushroom cloud’s diameter spanned 65 miles. U.S. forces had cleared a 60,000-square-mile danger zone around the test site, and residents of Bikini Atoll had already been evacuated years earlier for a 1946 U.S. nuclear test there. The bomb’s blast, however, was twice as powerful as scientists had anticipated, and along with an unpredicted shift in wind direction, radioactive fallout ultimately spread more than 7,000 square miles outside the danger zone. Two hundred and thirty-nine islanders, including children, elderly adults, and pregnant mothers, were exposed to radiation on four atolls more than eighty miles east of Bikini. Many developed symptoms of radiation illness. Twenty-eight American meteorological staff were also exposed as they observed the test from an island 155 miles east of the blast.