East Coast Tsunamis

Update, July 12, 2018: Researchers are still studying the Grand Banks tsunami today.

On February 6 this year, the US National Weather Service broadcast its routine monthly tsunami test alert. Something went wrong, and two private weather companies notified subscribers it was a real tsunami.

Hurray for routine test alerts! Mistakes can highlight errors and get them fixed. This one didn’t happen during an actual disaster and will probably result in more accurate tsunami real-time information for residents of eastern North America.

They need it.

While the Atlantic coast is a passive margin, unlike the western coast (where tectonic plates are colliding), tsunamis do happen there.

They even occur far from the coast!

All you need to make a tsunami is to displace a sizable amount of water. One quiet Sunday morning in April 1908, for example, an estimated 42.6 million cubic feet of land (1.2 million m3) slid into Quebec’s Lièvre River, causing a 50-foot (15-meter) wave on the opposite bank that killed 33 people.

Probably the most famous eastern North American tsunami came from the enormous 1929 underwater landslide that either caused or was triggered by a surprise M7.2 earthquake on the Grand Banks.

Almost 30 people died in Newfoundland and Nova Scotia in that disaster.

It’s interesting that one of the eyewitnesses in that video saw the approaching wave.

According to one study, the quake was felt in Newfoundland around 5 p.m. local time, and the waves arrived between 7:30 and 8 p.m., when it was dark.

The witness is convinced he saw that. It just might have been another tsunami. His description reminds me of aerial views I’ve seen on the news.

Such an error is very common and very understandable.

While I have never been in such a horrible disaster, I did witness a car plowing into a group of people at a bus stop, many years ago, and from my own recall of the event I know there can be problems with eyewitness accounts.

Your mind works differently in an emergency.

So remember this as you explore an interactive hazard map from NOAA for historical tsunamis.

The most reliable information comes from instruments, for example, measurements of maximum wave height (not much) from Woods Hole and Nantucket on June 13, 2013.

Nevertheless, the sheer volume of witnessed tsunami reports on this map, going back to the 19th century, shows that Atlantic Ocean tsunamis are a thing. They aren’t usually as dramatic as those in the west, but tsunamis did kill at least 60 easterners during the 20th century.

Featured image: The 1929 Grand Banks earthquake epicenter, NASA

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