The massive earthquake, which the U.S. Geological Survey revised to a magnitude of 9.0, from 8.9, and the 23-foot tsunami that devastated Japan on Friday, March 11, 2011, has also caused a nuclear crisis. Cooling systems at the Fukushima Daiichi Nuclear Power Station failed shortly after the earthquake. On Saturday, March 12, there was an explosion at reactor No. 1. Radioactive material was detected outside the plant. Officials feared that a meltdown may occur. By Sunday, officials believed that partial meltdowns had occurred in reactors No. 1 and No. 3. The cooling systems at Fukushima Daini, another plant, had also failed. More than 200,000 residents were evacuated from areas surrounding both facilities.