I WAS EXPECTING AN EARTH-SHATTERING KABOOM: Boffins identify ancient Earth asteroid strike that dwarfed dinosaur killer: Massive space rock impact may have set the continents sliding. “The impacting body, which could have been an asteroid or a comet, was between 37 and 58 kilometers (23 to 36 miles) wide and hit the Earth at 20 kilometers per second (12 miles per second). The impact would have caused a crater around 500 kilometers (about 300 miles) across and the resulting tsunamis would have been thousands of meters high.”