SinkholeOdds

Sinkhole risk in Newaygo County, MI: Sinkhole country

Sinkhole country

Fast-dissolving gypsum or salt beds under a large part of the county.

On soluble rock
54%
At or near the surface
0%
Buried under cover
54%

What to do about a house in Newaygo County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 450 of Newaygo County's 839 square miles on soluble rock. With about 51,504 residents (61 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 399 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: why gypsum and salt move faster than limestone, and why the 54% under cover still counts.

Counties around Newaygo County

The closest county with no soluble rock mapped is Mecosta County, MI, about 23 miles east. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Which formation it is

The largest mapped soluble unit here is the Michigan Formation (black shale), Mississippian in age, covering about 41% of the county. Next is the Bayport Limestone at 13%.

41% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

The county also lies over the Michigan Basin; Ohio Basin; Appalachian Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Michigan

Newaygo County ranks 65 of 83 in Michigan for soluble rock at the surface, and sits above 0% of US counties on that measure.