Sinkhole risk in Huron County, MI: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 31%
At or near the surface: 0%
Buried under cover: 31%

The next step for one property

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 259 of Huron County's 836 square miles on soluble rock. With about 30,780 residents (37 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 284 map points about 1.7 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Huron County

The nearest county rated sinkhole country is Tuscola County, MI, about 41 miles southwest. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Sanilac County, MI 33 mi south · 0% at surface
Tuscola County, MI 41 mi southwest · 0% at surface
Iosco County, MI 42 mi northwest · 0% at surface
Arenac County, MI 45 mi west · under 1% at surface
Alcona County, MI 56 mi northwest · under 1% at surface
Bay County, MI 58 mi west · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Michigan Formation (black shale), Mississippian in age, covering about 24% of the county. Next is the Bayport Limestone at 7%.

24% 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

Huron County ranks 40 of 83 in Michigan for soluble rock at the surface, and sits above 0% of US counties on that measure.