The reports of the devastation caused by the tsunami in south east Asia are truly depressing. The massive tidal wave was the result of an undersea earthquake off the coast of Sumatra. The ocean floor suddenly ruptured and rose up sending an enormous swell of water northwards toward India and Sri Lanka. Those unlucky souls by the coastline had little or no warning of the impending wave.
Could something like this happen to the United States? Some scientists report that a powerful volcanic eruption in the Canary Islands off the coast of Africa could trigger a tsunami which could devastate the east coast of the U.S.. In such a scenario, a 50 meter high wave would reach New York City about 8 hours after the eruption, completely subsuming the city.
Is it time to sell your beach front property? No, although this kind of tsunami is possible in the Atlantic, it's highly unlikely to occur in your lifetime.
On the other hand, newly discovered asteroid 2004 MN4 is currently estimated to have a 1 in 37 probability (!) of striking the Earth in 2029. Yikes!