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Sinkholes and mudslides: Are they a threat in Michigan?

By HEATHER HESSELINK
Staff Writer

Sinkholes and mudslides have been big news in the past few months all over the country — with a large sinkhole opening up inside the National Corvette Museum swallowing priceless cars near Mammoth Caves National Park in Kentucky, to the devastating mudslide in the state of Washington that wiped out an entire community in the blink of an eye.

This photo by the National Corvette Museum shows the devastation from its unexpected sinkhole

This photo by the National Corvette Museum shows the devastation from its unexpected sinkhole

It is common for most people to think that something like a sinkhole or mudslide can never happen in the state of Michigan. But what many people do not know is that Michigan does have a history of sinkholes.

Jonathan Miller, adjunct science instructor at Mid Michigan Community College, noted that there are sinkholes in the area around Alpena and Rogers City. “I found a YouTube link: Northeast Sinkholes. A sinkhole would occur when earth beneath the surface or substrate is removed to form a cavern-like structure. When the ceiling of this cavern collapses, a sinkhole is formed,” he explained. “Sinkholes can form both from natural processes and from failures in infrastructure like a broken water line eroding earth away below the surface. A broken water line was responsible for a sinkhole in Detroit in early April.”

With warmer weather and recent heavy rains, residents are wondering what the effect of a torrential rainfall could have on their own property. With the Washington state mudslide still fresh in many memories, local community members are left wondering how they can prevent themselves from falling victim to such events. In Michigan, sinkholes are more common than mudslides, where steep slopes are an important ingredient.

“With respect to becoming a victim, people should be extra cautious when living at the top of a slope or at the bottom of one, especially steeper slopes like a stream valley,” Miller advised. “A portion of the slope could fail which would send a higher structure crumbling down the slope or see a lower structure in the path of the slide, buried.”

A mudslide is created when water soaks the land beyond the level of saturation. Once that level is hit, water acts as an lubricant and with the help of gravity a mudslide can be easily created, even in Michigan.

Mudslides at a glance
* According to the online source Livescience, heavy rains aren’t the only thing that can trigger a mudslide.
* Mudslides are rivers of rock, earth and other debris that are saturated with water, according to the U.S. Geological Survey (USGS).
* Mudslides can be slow- or fast-moving, though they tend to grow in size and momentum as they pick up trees, boulders, cars and other materials.
* Mudslides can occur any time of the year, regardless of weather conditions, according to the Federal Emergency Management Agency (FEMA). And they can strike without any warning.
* Earthquakes, volcanic eruptions, changes in groundwater levels, alternate freezing and thawing, and the steepening of slopes by erosion all contribute to mudslides.
* Construction and reckless modification of land – such as not draining an area properly before building on or near it – can also create the conditions ripe for a mudslide.
* “Mudslides occur in all 50 U.S. states and can happen at any time – with or without rainfall,” said Lynn Highland, a geographer at the USGS National Landslide Center.

Sinkholes at a glance
* According to U.S. Geological Survey, a sinkhole is a depression in the ground that has no natural external surface drainage. When it rains, all of the water stays inside the sinkhole and typically drains into the subsurface.
* Sinkholes are most common in “karst terrain.” These are regions where the type of rock below the land surface can naturally be dissolved by groundwater circulating through them. Soluble rocks include salt beds and domes, gypsum, and limestone and other carbonate rock.
* When water from rainfall moves through the soil, these types of rock begin to dissolve and spaces and caverns develop underground. If there is not enough support for the land above the spaces, a sudden collapse of the land surface can occur.

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