outdoors Deborah k. Frontiera

Great Lakes tsunamis

How and why these surprising events take place

Story by Deborah K. Frontiera

When most people hear the word “Tsunami,” they think of those mighty earthquake-generated waves that kill hundreds or even thousands of people. “We don’t have earth quakes in this area,” one might state. But huge, destructive waves do happen on the Great Lakes more often than many people might like to admit.

In How the Rock Connects Us, a book by Bill Rose and Erika Vye, the authors state: “Waves higher than 40 feet have been recorded on Lake Superior. Waves build to breakers when the water gets shallow enough that the wave feels the lake bottom’s resistance. This occurs when the depth is about half the distance between the wave crests. The distance travelled by wind or waves over open water, known as the ‘fetch,’ is important for lakes with large surface areas like Lake Superior: the longer the fetch, the greater the strength of winds and height of waves.”

Two different types of “rogue waves” can, and do, happen on Lake Superior and the other Great Lakes.

One is known as a “seiche.” This large wave, or waves, occur as a result of quick changes in atmospheric pressure accompanied by heavy wind. It is the oscillation in the water level of a lake or large bay. Think about what happens when you blow down and across hot coffee, tea or chocolate in a big mug to cool it before drinking. Your breath is like the wind, and the downward push of that breath, like a drastic change in air pressure on the surface of the hot liquid. A little depression forms in the liquid and ripples or waves flow across the mug and wash up on the opposite “shore.” Blow hard enough, and you’ll slosh some out onto the table or saucer. If you wait a bit, the liquid will come back to your side. Now picture this in nature on the enormity of the Great Lakes. Water on one side diminishes enough to make it seem like “low tide” along that shore. On the opposite side, rising water can cause quite a bit of destruction. Another comparison is water sloshing back and forth in a bathtub.

The second type, known as a “meteotsunami,” is also caused by severe weather events, often formed on the western sides of the various Great Lakes because our weather patterns generally move west to east. High winds, usually in late spring and early summer, (the height of the thunderstorm season), when accompanied by rapid changes in atmospheric pressure, depress the lake on that side, forming a wave which then rolls in one direction across the lake. The wave’s height depends on the speed, intensity, depth of water and the shape of the lake at that particular place. That might seem exactly the same as the seiche. The key difference is that meteotsunamis roll in one direction, rather than “sloshing” back and forth. The resulting wave gains energy as it moves across the lake, especially as it nears the opposite shore.

Here are a few examples of Great Lakes Tusnamis from the history books: • July 4, 1929, a 20-foot wave crashed ashore at Grand Haven, Michigan and 10 people drowned. • June 26, 1954, a 10-foot wave swept 10 fishermen off a pier in Chicago and all 10 were lost. • July 4, 2003, a 10-foot wave drowned seven swimmers on the Lake Michigan shore near Sawyer.

Though the damage pictured here wasn’t caused by a tsunami, the image does provide an example of the destructive power of water. This image, taken just after a 2017 storm brought massive waves crashing over the shoreline, shows huge chunks of dislodged concrete in the Shiras Park parking lot. (Photo by Jackie Stark)

The phenomenon happens often enough that a group of experts gathered in Ann Arbor in the summer of 2016 to discuss what might be done to protect people along the shorelines of all the Great Lakes. At that gathering, it was reported that such waves happen over 100 times per year on all the Great Lakes combined.

In reporting on that gathering of scientists, the Detroit News (June 19, 2017) had this statement from Chin Wu of the University of Wisconsin.

“When they [the waves] recede, it’s like a vacuum . . . The energy of the recessing wave can last 10 to 20 minutes. So you can imagine a swimmer swept that far out into the lake and fighting it all that time.”

Besides the danger to people, several nuclear power plants are located on the shores of the Great Lakes. Such suction outward could remove all water from the intake cooling pipes, leaving the core reactors without cooling for several minutes. While this has not yet happened, scientists do have concerns about that possibility, no matter how low the odds against it.

Statistics show that meteotsunamis happen most frequently on Lake Michigan because of the prevailing westerly winds on that lake and its overall width. Lake Earie places second since it is situated west to east, letting prevailing winds blow across its entire length. Only one has been reported on Lake Superior — in the area of Sault Ste. Marie. Meteotsunamis have also been reported in other parts of the world: Vela Luka in Croatia (June 1978), Nagasaki Bay, Japan (Mar. 1979) and Longkou Harbor, China (Sep. 1980) to name a few.

Photographic evidence of the results of such a wave that hit the Ludington, Michigan breakwater on April 18, 2018 can be seen accompanying an article by Tony Briscoe of the Chicago Tribune (April 25, 2019). That article also reported the possible danger of “wash back” from such waves as they regain energy when flowing out. Theoretically, a wave could hit the eastern shore of Lake Michigan and then reflect back to the Chicago area where the weather might be quite fine, with no one suspecting anything could happen.

While the odds of experiencing a meteotsunami this spring or summer in Upper Michigan are very low, it is important to be aware of your surroundings or a quick change of weather. Here are a few recommended safety precautions: • If in a boat, keep in mind that even a 5-foot wave can overturn small boats. Head into deeper water where the effect will be less. • On shore, head inland toward high ground. • If caught in the outgoing rip current, float on your back, resting as much as possible, rather than fighting it and becoming tired; then swim parallel to the shore until you are out of the current before attempting to swim to shore.

About the author: Deborah K. Frontiera lives in the Calumet area. Three of her books have been award winners. She has published fiction, nonfiction, poetry and children’s books. Frontiera is on the board of the Upper Peninsula Publishers and Authors Association. For details about her many books and accomplishments, visit her website: www.authorsden.com/deborahkfrontiera