The Friends of Charles Darwin

One of the few remaining objections to the idea that an asteroid killed off the dinosaurs has been put to rest. The giant tsunami caused by the impact may have scrambled fossil evidence, explaining puzzling finds that suggested the asteroid and the mass extinction were unrelated. Many geologists have long argued that the Cretaceous period ended when a 10-kilometre-wide asteroid slammed into the Gulf of Mexico, just off the Yucat´n coast. That point in history bears the hallmarks of a global disaster - mass extinction, a giant crater, impact debris such as solidified rock droplets, and traces of iridium typical of an asteroid. However, fossils from the end of the Cretaceous have been found above layers of rock linked to the asteroid impact, and Gerta Keller of Princeton University has used this evidence to argue that the extinction may have come 300,000 years after the impact. Now Tim Lawton of New Mexico State University in Las Cruces and his colleagues have shown how fossil records could have been shuffled by the tsunami following the impact. Earlier evidence has shown that the tsunami may have been 150 metres high, carrying water up to 300 kilometres inland.