Sinkhole risk in Montgomery County, IN: 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: 6%
At or near the surface: 0%
Buried under cover: 6%

What this means before you buy

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

That works out to roughly 29 of Montgomery County's 505 square miles on soluble rock. With about 38,633 residents (77 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 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and why the 6% under cover still counts.

Counties around Montgomery County

The nearest county rated sinkhole country is Monroe County, IN, about 64 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Fountain County, IN 19 mi west · 0% at surface
Boone County, IN 22 mi east · 0% at surface
Tippecanoe County, IN 24 mi north · 0% at surface
Parke County, IN 24 mi southwest · under 1% at surface
Putnam County, IN 26 mi south · under 1% at surface
Hendricks County, IN 28 mi southeast · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Sanders Group (limestone), Mississippian in age, covering about 6% of the county. Next is the Blue River Group at under 1%.

The county also lies over the Illinois 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 Indiana

Montgomery County ranks 68 of 92 in Indiana for soluble rock at the surface, and sits above 0% of US counties on that measure.