As we recall the December 2004 tsunami that wreaked death and destruction in Indonesia and watch in horror the current coverage of the disastrous tsunami in Japan, a reasonable question is: Could a tsunami strike the East Coast, including one significantly impacting the Washington D.C. area?
The short answer is YES, though with much lower probability and generally not as catastrophic as a tsunami hitting the West Coast.
However, while there is no indication it could happen soon (but could), there are scientifically sound reasons for concern that at some point a mega-tsunami could engulf the entire East Coast with a wave almost 200 feet high sweeping everything and everybody up to 20 miles inland. The consequences of such a relatively unlikely but very possible event in loss of life and property are inestimable and beyond the realm of imagination (at least for me).
(Note: Not withstanding covering the potential catastrophe associated with space weather and tsunami possibilities here, please trust that I am just reporting and not a wild-eyed irrational prophet of doom. This is real science, not science fiction.)
Most large tsunamis occur in the Pacific and originate along the hotbed of seismic activity (earthquakes and volcanism) referred to as the Pacific Ring of Fire. Tsunamis, such as the 2004 Indonesian and recent Japan catastrophes occur in response to the sudden vertical uplift of tremendous volumes of water by an earthquake where one tectonic plate slides beneath another (subduction).
By contrast, the Atlantic Ocean is home to much less seismic and volcanic activity than the Pacific and, in particular, lacks subduction zones which are most common source of tsunami-causing earthquakes.
The majority of earthquakes capable of generating tsunamis in the North Atlantic are associated with the Lesser Antilles subduction zone near Puerto Rico. Historically the majority of these resulted in localized damage and death but nothing on a regionally catastrophic scale outside of the Caribbean. In 1918, for example, a magnitude 7.3 earthquake off the northwest coast of Puerto Rico generated a tsunami with a height of about 20 feet causing extensive damage and killing over 100 people. Waves with amplitudes between (1 and 3 inches) were recorded on an Atlantic City, NJ, tidal gage, but were otherwise barely noticeable there or elsewhere along the East Coast.
However, tsunamis affecting the East Coast are much more likely to be caused by earthquakes, which alone would not likely produce a tsunami, but could indirectly by causing underwater or island landslides that vertically displace large volumes of water. The most noteworthy in recent history occurred in 1929 when a tsunami was generated by a submarine landslide triggered by a major earthquake (magnitude 7.1) 250 miles south of Newfoundland (and felt as far south as New York). Tsunami wave heights ranged from about 6 to 23 feet and were concentrated on the coast of Newfoundland (killing 28 people) but recorded as far south as South Carolina.
Some other tsunamis affecting the East Coast include:
• November 14, 1840 - Delaware River: referred to as “The Great Swell on the Delaware River”
• January 9, 1926 – Maine: No one was injured, but “monster waves” hurled 50 fishing boats ashore and washed thousands of flounder from their winter beds in the Harbor bottom mud”.
• Aug 19, 1931 Atlantic City, NJ 3 Dead
• Sep 21, 1938 New Jersey coast Scores injured, some seriously
• Jul 3-4, 1992 Daytona Beach, FL 75 injured
Additionally, there are many confirmed and unconfirmed tsunami events that resulted in localized flooding. Unfortunately documentation of these and other comparable events, including their origin, are sparse but believed to be associated directly or indirectly with relatively nearby earthquakes. None in the contemporary record came close to being as disastrous as those we’ve seen in the Pacific.
But this does not mean it cannot happen, and in fact probably will. What cannot be foretold at this time is when.
Scientists have established at least two time bombs that could lead to a mega-tsunami hitting the U.S. East Coast.
The first is a submarine landslide at the edge of the continental shelf off the coasts of Virginia and North Carolina where unstable sections of the shelf could collapse into the trenches of the deep ocean. Should that occur scientists believe an 18-foot-high tsunami would propagate towards the coast and strike in a matter of hours.
The second time bomb is a mega-tsunami caused by a massive landslide as a large section of La Palma, one of the Canary Islands in the Eastern Atlantic, collapses into the ocean following a volcanic eruption of the Cumbre Vieja volcano on La Palma. If (when) this occurs, modeling results indicate a wall of water up to 300 feet high would race across the Atlantic and reach the East Coast in about nine hours with devastating effects.
A video from a Discovery Channel Special (minutes 3-6) has a vivid portrayal illustrating this phenomenon, including an explanation of why Washington and Philadelphia are particularly vulnerable due to the focusing of wave energy by the shape of the Chesapeake Bay.
An event of this extreme magnitude caused by a landslide into the open ocean is extremely rare. The last one happened 4,000 years ago on the island of Réunion. However, there are growing concerns that the ideal conditions for just such a landslide - and consequent mega-tsunami - now exist on the island of La Palma. However, there is no agreement on the probability of this occurring in the near future other than to note it is much less likely than large earthquake-driven tsunamis typical of the Pacific basin.
Personally, I’d be more worried about hurricanes and tornadoes and even moreso about prospects for a global catastrophe resulting from a worst case scenario solar storm.