Sinkhole risk in Lawrence County, IN: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 75%
At or near the surface: 71%
Buried under cover: 4%

What this means before you buy

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

That works out to roughly 336 of Lawrence County's 449 square miles on soluble rock, 319 of them with the rock at or near the surface. With about 45,192 residents (101 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 384 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 the signs to look for and how an inspection works.

Counties around Lawrence County

The closest county with no soluble rock mapped is Brown County, IN, about 28 miles northeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Martin County, IN 19 mi southwest · 23% at surface
Orange County, IN 20 mi south · 90% at surface
Monroe County, IN 22 mi north · 54% at surface
Jackson County, IN 24 mi east · 2% at surface
Washington County, IN 26 mi southeast · 62% at surface
Brown County, IN 28 mi northeast · 0% at surface

What Lawrence County is built on

The largest mapped soluble unit here is the Blue River Group (limestone), Mississippian in age, covering about 33% of the county. Next is the Sanders Group at 28%.

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

Lawrence County ranks 4 of 92 in Indiana for soluble rock at the surface, and sits above 93% of US counties on that measure.