Tsunamis Can Actually Be Created By Weather

People run as a meteotsunami crashes shore on Captiva
Island, Florida on Friday

A lot of us have read in horror about the tsunami that swept through an Indonesian seaside town over the weekend during a rock concern on the beach. The disaster killed nearly 400 people. 

Unlike the overwhelming majority of tsunamis, this one wasn't created by an earthquake. Instead, it looks like a volcano erupted, triggering a huge landslide on one side of the volcano, which then plunged into the sea.

This in turn created the huge waves that caused so much death and destruction and sorrow this weekend in Indonesia.

As noted, almost all tsunamis are created by earthquakes. The earth thrusts during a a big tremor, and that lifts a vast amount of water. When this mass of water nears shore, it encounters shallower water, so it builds up into immense waves that create these big disasters.

Weather can also create tsunamis of sorts, but luckily they're almost never as bad as the ones induced by earthquakes. Still they can cause a lot of damage.

On Friday, one such tsunami hit Captiva and Sanibel islands  Florida. These are called meteotsunamis.

I'll let NOAA explain what they are:

"Meteotsunamis are large wave that scientists are just beginning to better understand. Unlike tsunamis triggered by seismic activity, meteotsunamis are driven by air pressure differences often associated with fast-moving weather events such as severe thunderstorms, squalls and other storm fronts. The storm generates a wave that moves towards the shore, and is amplified by a shallow continental shelf, bay or other coastal feature."

That's what happened Friday at Captiva Island, Florida. A powerful squall line associated with that strong storm slammed into the western shore of the Sunshine State Friday. The squall line surged water ahead of it, and when the wave encountered shallower water off Captiva Island, the wave piled up, then crashed ashore.

The Captiva Island meteotsunami caused damage, but it wasn't the worst one ever.  Says NOAA: "Meteotsunamis have been observed to reach heights of six feet or more. They occur in many places around the world, including the Great Lakes, Gulf of Mexico, Atlantic Coast and the Mediterranean and Adriatic Seas."

Even where they do sometimes occur, meteotsunamis do surprise people.   A squall line on May 15 caused an unusually severe outbreak of tornadoes and high winds in southern New England and the Mid-Atlantic states.

The tornadoes of course dominated the news, but the pressure changes associated with the squall line were intense enough to cause a meteo-tsunami along the coast from Connecticut to Maryland. This wasn't a damaging tsunami, as waves never got above 10 inches over normal high tides. But it was an unusual event, proving the atmosphere can influence the vast oceans as well.

Florida seems particularly prone to meteotsunmis. Perhaps one of the worst meteotsuamis in U.S history hit during the massive "Storm Of The Century" blizzard of March, 1993. As areas from Georgia to Maine were buried in up to three feet of snow, a squall line associated with the storm slammed into western Florida, causing a destructive meteotsunami.

A year earlier, a meteotsunami injured 75 people in Daytona Beach, Florida. Other ones hit in 2014 and 2016.

Most meteotsunamis aren't this destructive.  The vast majority are too small for most people to notice, but are picked up by tidal and water level guages.

There's another related phenomenon called a seiche. That's when strong winds, often shifting, push water in a lake onto one shore, then the water sloshes back to the other side, much like water can slosh in a bathtub if you move around too much.

Seiches, like meteotsunamis, can easily cause shoreline flooding.

Here's video of the meteotsunami in Florida on Friday. As you can see, they an be quite dramatic: