|Fig. 1: NASA Earth Observatory image of Castle Bravo crater in Bikini Atoll coral reef taken by Landsat8-OLI on 19 Aug 13. (Courtesy of NASA)|
On March 1, 1954, the United States Army conducted the largest thermonuclear weapons test in history in Bikini Atoll, Marshall Islands, home to a vibrant and diverse ecological community including one of the world's pristine fringing coral reefs.  The detonation, expected to produce 4-6 megatons, exceeded predicted yield nearly threefold and was estimated at 15 megatons, equivalent to 1000 times more powerful than the atomic weapon used on Hiroshima in 1945. The weapon caused devastating impact to the fringing coral reef, contaminated the surrounding communities and spread radioactive debris high into the stratosphere, eventually spreading to 4 continents. 
The Castle Bravo thermonuclear device, part of Operation Castle, was the largest ever detonated. The demonstration was notoriously harmful, being a surface detonation, resulting in the largest fallout and spread of any thermonuclear device to date. The detonation caused immediate damage to the submarine fringing reef which has not fully recovered to date. Figure 1 shows the two-kilometer wide crater left in the fringing coral reef from the immediate explosion as imaged by NASA's Landsat 8 operational land imager in 2013. It is notable that the fringing reef has not replaced the excavated area in the intervening 59 years and that regrowth of the coral community was slow and lacking in diversity in the first few decades after testing.  Since, recent studies have shown resilience in the biodiversity of the local coral community, but a large portion of reef substrate was irreparably lost, decreasing coastal protection factors for the surrounding atoll. 
Apart from the physical vaporization of reef structure, the explosion caused rapid thermal and kinetic stress to the surrounding water and spewed radioactive material into high altitudes and nearby environments, drawing international attention to the wide-spread atmospheric contamination. This partly led to the 1963 Nuclear Test Ban Treaty which prohibited surface tests of thermonuclear weapons. Between 1946 and 1958, over 23 nuclear weapons were tested at Bikini Atoll, with nearly one thousand native people forcibly evacuated. Since testing, the island remains largely uninhabited and radioactively contaminated.
© Ved Chirayath. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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