Three scientists have been working on computer models of asteroids colliding into the ocean. The biggest effect would be tsunamis, or giant waves emanating outward from the impact site.

An asteroid the size of one kilometer (or .6 miles) wide, moving at a speed of 45,000 miles per hour, can create tsunami waves a half-mile high that move at 380 miles per hour. A solid iron asteroid would vaporize quickly as it threw jets of water splashing more than 12 miles into the air. The water falls back to the ocean creating tsunamis that radiate away from the impact site. The wave would begin at 2,500 feet high, and drop to about 1,700 feet after traveling about 40 miles from the point of impact. A one-kilometer iron asteroid would strike with a force equal to 1.5 trillion tons of TNT. It’s equal to the energy released by 1.5 million 1-megaton nuclear weapons.

It’s hard to imagine what kind of coastal damage a 1,700- foot tsunami could do. Naturally occurring Earth-based tsunamis are much smaller but can do tremendous damage. A 30-foot high tsunami hit Papua New Guinea in 1998 and killed 2,100 people. In Louisiana, a 15-foot high hurricane tide traveled 20 miles inland.

There is only a 1 in 200,000 chance that a 1-kilometer iron asteroid will collide with Earth in any year. Astronomers around the world are cataloging asteroids and their orbits, searching for Earth threatening possibilities.