Here’s some more interesting physics about tsunamis, from an op-ed piece in today’s New York Times:

Oddly, a tsunami cannot be felt as it passes ships on the open ocean, for the wave is usually small, one to two feet, and traveling very fast, as fast as airliners. It is only as it approaches shallow water that it begins to break; as the bottom of the wave slows, the top keeps traveling at the higher speed and increases in height, hitting landfall at 30 to 40 miles an hour. In 1958, an earthquake in Lituya Bay, Alaska, caused a landslide into the ocean that created a tsunami 1,720 feet high, a wave that could have swept over the Empire State Building. Fortunately it headed into a wilderness area and did not travel across the ocean to Hawaii or Japan.

The really sad thing is, despite the difficulty of detecting an earthquake-generated tsunami, scientists did in fact figure out that one was headed for Sri Lanka — and in fact they had several hours of warning. It’s just that there wasn’t a warning system in place for that part of the world.

In other news, several experts have noted that there’s a 12-mile-wide chunk of Cumbre Vieja volcano on the Canary Islands that is ready to fall into the Atlantic. Apparently it was loosened by a 1971 eruption, and as the New York Daily News reports:

If and when the 500 billion tons of barely hanging rock finally barrels into the Atlantic, it could make the disaster flick “The Day After Tomorrow,” look like a joke, experts say. Prof. Bill McGuire, of the Benfield Hazard Research Center at University College in London, said the largest tidal wave ever would race across the Atlantic at up to 600 mph and hit New York as well as shorelines from the Caribbean to Boston.

Towering waves of up to 75 feet would engulf the city, traveling miles inland, destroying everything in their path, he told the Daily News in August.

(Thanks to Rachel for the Daily News link!)