| Original caption: “Atomic cloud during Baker Day blast at Bikini.” Baker Day A-Bomb Underwater Explosion Seen From Bikini Atoll. The Baker bomb was detonated by Los Alamos scientists inside its steel and concrete caisson, suspended 90 feet (27 meters) beneath USS LSM-60, and approximately 90 feet above the lagoon bottom. Energy release was similar to the Able shot, estimated to have yielded approximately 20.3 kilotons. A fireball was formed that illuminated the water with an orange-white light for a few millionths of a 2nd before the high-pressure gases of the ball erupted to the surface. The shock wave formed a “blast slick” of white water on the surface, emanating out from the 0 point in a “rapidly advancing circle” formed by the hurtling of small water droplets short distances into the air. Immediately, within 4 millionths of a 2nd, the gas bubble burst into the air, throwing up a mound of super-heated steam and water called the “spray dome,” at a rate of 2,500 feet per 2nd (762 meters per 2nd). The spray dome climbed into a column in which the water in the center moved faster than the water farther out, at a rate estimated at 11,000 feet per 2nd (3,350 meters per 2nd). This formed a hollow center in the column that acted as a chimney for the hot gases and superheated steam from the now nearly exhausted fireball to climb, carrying excavated lagoon bottom and radioactive products up to form, with water vapor, a cauliflower-shaped mushroom cloud. At the same time, the condensation of the water formed a vast “Wilson Cloud” around the column 18 seconds after detonation, which dispersed into a dissipating ring of clouds that vanished after 30 seconds. The United States Navy estimated this column was 2,200 feet (670 meters) in diameter at its base, and extended 6,000 feet (1,800 meters) skyward. It displaced 2,000,000 tons of water. The mushroom cloud was estimated to cover 10 square miles (26 square kilometers). The dark mark is often claimed to be the upturned hull of the battleship USS Arkansas (BB-33), but instead it is a void created by the stern as it was on fire and smoking as the water column expanded. The “Baker” detonation sank 9 vessels and badly damaged another 11 within a 1,000-yard radius of the 0 point. Joint Task Force 1, tallying the results, determined that 700 yards was a “serious if not fatal” damage zone, with serious damage at 900 yards, moderate damage at 1,000 yards, and slight damage at 1,500 yards. The majority of damage was caused by 2 factors — underwater shock, and the violent motion caused by it, as well as the impact with and violent motion from the blast-induced waves. 5 of the vessels not sunk within the 1,000-yard radius were “immobilized.” USS Pensacola (CA-24) suffered moderate hull dishing, damage to bulkheads, stanchions, and machinery foundations, holding down clips on turrets and battery mounts. USS Hughes (DD-410) was the closest destroyer to the 0 point. It suffered major structural damage, including ruptured pipes and sea connections which flooded the ship, dished plating, and a badly damaged rudder and skeg. A nearby ship had worse damage. USS Gasconade (APA-85) suffered a complete loss of longitudinal strength, the wrinkling of the bottom and shell plating, and partial flooding. The difference in damage was attributed to Hughes’ broadside mooring and Gasconade’s stern-to mooring. Gasconade rode the waves perpendicularly and hogged and sagged, while Hughes rode them parallel and consequently had its bottom and keel constantly supported by water. The transport USS Fallon (APA-81) was flooded to the waterline, with “severe structural damage to ship girders,” buckled decks and plates, and a permanent “transverse-curvature twist in her hull.” USS LST-133 had minor hull damage and cracked ballast tanks. Damaged but not immobilized were the destroyer USS Mayrant (DD-402), with bulkhead, stanchion, and weather deck damage and minor flooding from ruptured pipes, the battleship USS New York (BB-34), the transports USS Briscoe (APA-65) and USS Brule (APA-66), the already wrecked submarine USS Skate (SS-305), and USS LCT-816. | |
| Image Filename | wwii1947.jpg |
| Image Size | 679.73 KB |
| Image Dimensions | 2880 x 2372 |
| Photographer | |
| Photographer Title | United States Navy |
| Caption Author | Written or Adapted by Jason McDonald |
| Date Photographed | July 25, 1946 |
| Location | |
| City | |
| State or Province | Bikini |
| Country | Marshalls |
| Archive | National Archives and Records Administration |
| Record Number | NWDNS-80-G-396229 |
| Status | Caption ©2026 MFA Productions LLC Please Do Not Duplicate or Distribute Without Permission; Image in the Public Domain |
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