Some asteroids have orbits that cross the orbit of the Earth. That means that the Earth will be hit sometime. Recent studies have shown that the Earth has been hit an alarmingly large number of times in the past. One large impact is now thought to have contributed to the quick demise of the dinosaurs about 65 million years ago. The oceans cover about 75% of the Earth's surface, so it is likely the asteroid will hit an ocean. The amount of water in the ocean is nowhere near large enough to "cushion" the asteroid. The asteroid will push the water aside and hit the ocean floor to create a large crater. The water pushed aside will form a huge tidal wave, a tsunami. The tidal wave height in meters = (distance from impact)-0.717 × (energy of impact)0.495/ (1010.17). What this means is that a 10-km asteroid hitting any deep point in the Pacific (the largest ocean) produces a megatsunami along the entire Pacific Rim. The steam blasts from the water at the crater site rushing back over the hot crater floor will also produce tsunamis following the initial impact tsunami and crustal shifting as a result of the initial impact would produce other tsunamis---a complex train of tsunamis would be created from the initial impact.