There is significant evidence that a mass extinction of most land animals occurred 65 million years ago, probably because of a gigantic meteorite strike in the Gulf of Mexico. The impact is believed to have led to dustlike clouds encircling the globe, blocking out the sun's rays and halting photosynthesis in plants, which in turn affected the food chain. (In the Footsteps of Eve)
During the Miocene, between 13 million and 5 million years ago, sea levels were some 400 feet above their present levels. Should humanity survive the next 10,000 years, the odds are that the world's famous coastal cities - New York, Hong Kong, Sydney, London, and even Cape Town - will all be underwater archaeological relics. (In the Footsteps of Eve)