出典:Wiktionary
出典:Wikipedia
出典:『Wikipedia』 (2011/07/13 03:11 UTC 版)
An impact winter is a period of prolonged cold weather caused by the impact on the Earth of a large asteroid or comet. If such an impact occurred on land or the floor of a shallow sea, it could cause large amounts of dust or ash to be thrown into the Earth's atmosphere, blocking the Sun's light and dramatically lowering the amount of sunlight reaching the Earth's surface. Impact winter is one of the mechanisms proposed for extinction events, such as the asteroid impact at Chicxulub in Mexico which supposedly led to the extinction of the dinosaurs.