Sinkhole risk in Marion County, OH: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 77%
At or near the surface: 0%
Buried under cover: 77%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 309 of Marion County's 404 square miles on soluble rock. With about 64,976 residents (161 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 303 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 77% under cover still counts, and the signs to look for and how an inspection works.

Counties around Marion County

The nearest county rated sinkhole country is Monroe County, MI, about 93 miles north. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Wyandot County, OH 19 mi northwest · 0% at surface
Morrow County, OH 20 mi east · 0% at surface
Crawford County, OH 22 mi northeast · 0% at surface
Union County, OH 23 mi southwest · 0% at surface
Delaware County, OH 23 mi south · 0% at surface
Hardin County, OH 26 mi west · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Tymochtee and Greenfield Formations, Undivided (dolostone (dolomite)), Silurian in age, covering about 23% of the county. Next is the Salina Group at 22%.

Against the rest of Ohio

Marion County ranks 53 of 88 in Ohio for soluble rock at the surface, and sits above 0% of US counties on that measure.