Columbia University’s Lamont-Dougherty Earth Observatory has estimated the probability of a tsunami striking the Eastern Seaboard in a given year as less than 1,000 to one. But every so often something happens to shake us from our seismic slumber.

Such an event occurred in Maine last Oct. 28, when a series of 4-to-12-foot waves suddenly crashed ashore at Boothbay Harbor. The waves struck on an otherwise peaceful day when the tide was low. If they had arrived at high tide, much of the town’s waterfront might have been inundated. As it was, the waves caused extensive damage to piers and boats.

Their localized nature suggested that the waves may have originated in the Gulf of Maine, perhaps the result of slumping on one of the seamounts not far offshore. Such phenomena are rare, but hardly unknown. A 90-foot “tidal wave” set off by a 7.2-magnitude undersea earthquake swept Nova Scotia and Newfoundland in 1929, killing dozens of people on Newfoundland’s remote Burin Peninsula.

In the North Atlantic Basin, there are two areas of particular concern. One is the outer Continental shelf off Virginia and North Carolina. The shelf there abruptly drops off to the abyssal plain three miles below. Some 18,000 years ago, about 33 cubic miles of the cliff collapsed. The event created a series of huge waves that left geological evidence across the Carolina and Georgia “Low Country.”

Seismologists worry more about Las Palmas, a volcanic island in the Canaries, off North Africa. An eruption of the volcano Cumbre Vieja, which last blew in 1949, could send a large part of the western side of the island tumbling into the sea, creating waves that could pound the entire Eastern Seaboard, as well as much of the South American, Caribbean and European coasts.

The Caribbean, where the North American tectonic plate is subducted beneath the Caribbean plate in the Puerto Rico Trench, the Atlantic’s deepest point, is also seismically active, and subject to relatively frequent tsunamis. The Bahamas are a buffer, however, for most of the East Coast.

If a tsunami were to strike the East Coast, it could be severe because of its generally shallow and more gradually sloping undersea topography and low-lying littoral, indented by numerous bays and inlets, which would magnify incoming waves.

Because they are rare, there is no tsunami-warning system for the Atlantic Basin comparable to that for the Pacific. The lack of such a system for the countries of the Indian Ocean became apparent in the Dec. 26, 2004, tsunami that devastated much of coastal India, Sri Lanka and Indonesia. For the East Coast, the probability of damage from hurricanes is obviously greater, but because so many East Coast Americans live in low-lying coastal areas, evacuation plans for a tsunami event should be put into place, too.