Now don't say they didn't warn you about this!
Massive tsunami sweeps Atlantic Coast in asteroid impact scenario for March 16, 2880
If an asteroid crashes into the Earth, it is likely to splash down somewhere in the oceans that cover 70 percent of the planet's surface. Huge tsunami waves, spreading out from the impact site like the ripples from a rock tossed into a pond, would inundate heavily populated coastal areas. A computer simulation of an asteroid impact tsunami developed by scientists at the University of California, Santa Cruz, shows waves as high as 400 feet sweeping onto the Atlantic Coast of the United States.The probability that this asteroid would indeed crash into Earth is about 0.3% which is quite low. But consider the effects if indeed the asteroid crashed...
link via Slashdot
The 60,000-megaton blast of the impact vaporizes the asteroid and blows a cavity in the ocean 11 miles across and all the way down to the seafloor, which is about 3 miles deep at that point. The blast even excavates some of the seafloor. Water then rushes back in to fill the cavity, and a ring of waves spreads out in all directions. The impact creates tsunami waves of all frequencies and wavelengths, with a peak wavelength about the same as the diameter of the cavity. Because lower-frequency waves travel faster than waves with higher frequencies, the initial impulse spreads out into a series of waves.Errr... not very comforting, is it?!!