Sinkhole risk in Spencer County, IN: No soluble rock mapped

No soluble rock mapped

No soluble bedrock mapped.

On soluble rock: under 1%
At or near the surface: under 1%
Buried under cover: under 1%

What this means before you buy

No soluble bedrock is mapped here, so natural sinkholes are unlikely. Collapses from broken pipes or old mines are a separate risk.

That works out to roughly 2 of Spencer County's 397 square miles on soluble rock. With about 20,192 residents (51 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 520 map points about 0.9 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 how these percentages are measured.

Counties around Spencer County

The nearest county rated sinkhole country is Breckinridge County, KY, about 35 miles southeast, close enough that the same rock may run under the county line. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Warrick County, IN 15 mi northwest · 0% at surface
Hancock County, KY 17 mi southeast · 6% at surface
Daviess County, KY 20 mi south · 0% at surface
Perry County, IN 21 mi east · 49% at surface
Dubois County, IN 26 mi north · 5% at surface
Pike County, IN 29 mi northwest · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Buffalo Wallow Group (shale), Mississippian in age, covering about under 1% of the county.

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

Spencer County ranks 33 of 92 in Indiana for soluble rock at the surface, and sits above 50% of US counties on that measure.