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Quake shakes Mendota lake

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Also by Ken Harris:

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Quake shakes Mendota lake (February 1, 2008)
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by Ken Harris

Friday, February 1, 2008

Dropping temperatures caused the ice on Lake Mendota to crack Thursday afternoon, shaking the University of Wisconsin campus and giving students another reason to curse the cold.

When the ice shifted on the lake around 12:50 p.m., there was a loud bang and buildings along the lakeshore shook for two to three seconds.

UW senior Matt Yale was in Elizabeth Waters residence hall when the “ice quake” occurred. He said the doors rattled, and a lot of students came out into the halls, though nothing fell off shelves or broke.

“It was over really quickly,” Yale said. “We were speculating all different things like something hit the building or something.”

UW Police Department Sgt. Ben Newman said UWPD immediately received three to five calls from different campus buildings across the lakeshore, asking them to investigate the shaking.

Newman said UWPD officers began investigating right away and discovered the cause “rather quickly.”

“There was no damage that we know of,” Newman said.

According to UW seismology professor Cliff Thurber, the UW geology department was able to pick up the vibrations on their seismograph more than a half mile away from where the crack is believed to have occurred.

“It was about a zero on the Richter scale,” Thurber said.

According to Thurber, the reason for the ice cracking was due to the big temperature drop the city just experienced. Ice expands when the temperature drops drastically, causing the entire ice sheet to grow. Because the ice sheet is already pressed against the shore and has nowhere to go, the “big sheet cracks within itself like a fault,” he said.

Thurber said he believes the fault is probably parallel to shore and 100 feet or so away from it. He added anyone within a few hundred feet would have felt the vibrations. “Anyone out of doors on campus could have heard the sound,” he said.

Though the “ice quake” may have seemed like an earthquake, Thurber said the event looked nothing like an earthquake on the seismograph.

Earthquakes occur very deep in the ground and send waves outward, and these waves behave like concentric circles so when they reach earth’s surface, they affect a relatively wide area, according to the Thurber.

Thursday’s quake was felt in a fairly small area because the ice quake happened at the surface.

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Anonymous (February 1, 2008 @ 11:33am):

Why wouldn't the headline say Lake Mendota instead of Mendota lake? Was that capital "L" just too much?

Anonymous (February 1, 2008 @ 4:51pm):

Yeah, who would ever print Michigan lake, not Lake Michigan?

Anonymous (February 1, 2008 @ 5:48pm):

Besides the awkward title (great job news editors), this is why I love Madison.

Anonymous (February 1, 2008 @ 7:33pm):

Ice does not expand as temperature drops. It does exactly the opposite - It contracts. Most materials are similar, expanding with increasing temps and contracting with decreasing temps. The physical property is called "the Coefficient of Thermal Expansion (and Contraction).

The ice sheet on a frozen lake is firmly attached (frozen) to the shoreline. As the temp drops and the ice sheet contracts, large tensile strains build up until they reach the elastic limit of ice.... and 'zing' goes a crack across the brittle sheet of ice. As this contraction continues with falling temperature, it causes cracks to develop in the ice sheet which immediately fill with water and freeze again. Most ice fishermen know that ice 'talks' a lot when the temperature is dropping. The noises are made by the cracks as the tensile strain is released.

When the temperature rises back towards 32F again, the ice sheet must expand. But all of those cracks induced during the cold snap have filled with water and frozen tight again. With the ice sheet firmly frozen to the shoreline all the way around the lake and prevented from expanding, large compressive strains build up in the ice sheet. When it reaches a critical point, something has to give, so either the sand/rocks/shoreline gets pushed back a bit or "BOOM" - the compressively loaded ice sheet breaks violently (and loudly!) and an 'ice heave' or 'ice ridge' forms. On large lakes like Big Green Lake, the ridges can be 6' high and run across the lake width. The "BOOM" concussion sounds like a large explosion!

Let's review.
1) Ice contracts with decreasing temperature and expands with increasing temperature.

2) If the temperature is dropping, the lake ice makes 'zing', 'spoing', and 'sqeeeeuw' noises as it contracts and cracks. Sounds like Star Wars sound effects!

3) If the temperature is rising, the ice may make a loud "BOOM" as the ice expands and an ice ridge or heave is violently formed.

Engineering Alumni and Ice Fisherman

Anonymous (February 2, 2008 @ 9:50am):

I think it is meant to rhyme with Quake.

It sounds more catchy that "Quake shakes lake Mendota"

See it doesn't rhyme/ isn't as catchy.

Anonymous (February 3, 2008 @ 4:45pm):

It's catchy folks......sheesh

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