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Researchers from the University of Cincinnati have found evidence of a cosmic cataclysm 1,500 years that may be responsible for the downfall of the Hopewell Culture. The Hopewell Culture was a widely dispersed set of pre-Columbian Native American populations connected by a common network of trade routes from 100 BC to AD 500 in the Middle Woodland period. The researchers found evidence of a cosmic airburst at 11 Hopewell archaeological sites in three states stretching across the Ohio River Valley in the United States, which rained debris down into the Earth’s atmosphere creating a fiery explosion around 1,500 years ago...

Nearly 1,500 years ago a massive flood in Geneva reportedly swept away everything in its path -- mills, houses, cattle, even entire churches. Now researchers believe they've found the unlikely sounding culprit: a tsunami-like killer wave in the Alps. The threat, they add, may still be very much alive. (Video: Tsunamis 101.) Spurred by a huge landslide, the medieval Lake Geneva "tsunami" (technically defined as a seismic ocean wave) swamped the city, which was already a trading hub, according to a new study. Far from any ocean, the massive wave was likely generated by a massive landslide into the Rhone...

Double impact may have caused tsunami, global cooling Pieces of a giant asteroid or comet that broke apart over Earth may have crashed off Australia about 1,500 years ago, says a scientist who has found evidence of the possible impact craters. Satellite measurements of the Gulf of Carpentaria (see map) revealed tiny changes in sea level that are signs of impact craters on the seabed below, according to new research by marine geophysicist Dallas Abbott. Based on the satellite data, one crater should be about 11 miles (18 kilometers) wide, while the other should be 7.4 miles (12 kilometers) wide....