Past supermoons have coincided with natural disasters--the Indonesian earthquake in 2005, Australian flooding in 1954--but scientists note that those are unrelated, more likely than not. Says John Bellini, a geophysicist at the U.S. Geological Survey: "A lot of studies have been done on this kind of thing by USGS scientists and others. They haven't found anything significant at all." The tides will pull a bit higher, but earthquakes are almost completely unaffected and volcanoes are not likely to show unusual behavior. John Vidale, a seismologist at the University of Washington in Seattle, said "Practically speaking, you'll never see any effect of lunar perigee. It's somewhere between 'It has no effect' and 'It's so small you don't see any effect.'"