Landslides, tsunamis and earthquakes caused by testing



From 1975, all nuclear blasts were carried out underground, causing both short-term and long-term environmental damage. At the time of the explosion, fracturing of the atoll surface triggered landslides, tsunamis and earthquakes. A report by the IPPNW and the Institute for Energy and Environmental Research on the Environmental Effects of French Nuclear Testing found evidence that radionuclides were vented into the environment. Possible long-term effects include leakage of fission products to the biosphere and transfer of dissolved plutonium from the lagoon to the ocean and the food chain. A number of scientific missions to Moruroa described severe impairment to the atoll. The damage included fissures in the limestone which are propagated by the testing, and surface subsidences of large areas of the atoll.



At least one major test-related landslide and consequent tsunami occurred in Moruroa on 25 July 1979. The report on the Environmental Effects of Nuclear Testing claims that a 120 kiloton weapon that was being tested, became stuck inside the shaft and could not be dislodged but was exploded anyway. The explosion resulted in a major underwater landslide of at least one million cubic metres of coral and rock and created a vast cavity. The underwater landslide produced a major tidal wave comparable to a tsunami, which spread through the Tuamotu Archipelago and injured people on the southern part of Moruroa.



Radionuclides detected in marine organisms

A mission in 1983 to Moruroa comprising scientists from Australia, New Zealand and Papua New Guinea identified unusual concentrations of iodine-131 (I-131) in marine organisms. Krypton-85 and tritium (see Chart 1) were also discovered in the air and water, indicating that venting had occurred. In 1987, a mission to the region by the scientist and researcher, Jacques Cousteau, found raised levels of I-131 in all sediment samples and plankton. Since I-131 has a short half life of 8.05 days, its presence could only be attributed to a recent emission.