Sinkhole risk in Lawrence County, SD: Pockets of it

Pockets of it

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

On soluble rock: 42%
At or near the surface: 42%
Buried under cover: 0%

What this means before you buy

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 336 of Lawrence County's 800 square miles on soluble rock, 336 of them with the rock at or near the surface. With about 28,809 residents (36 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 333 map points about 1.6 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 nearest county rated sinkhole country is Fall River County, SD, about 79 miles south. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Butte County, SD 41 mi north · 6% at surface
Crook County, WY 41 mi northwest · 42% at surface
Custer County, SD 49 mi south · 30% at surface
Weston County, WY 51 mi southwest · 14% at surface
Pennington County, SD 54 mi southeast · 13% at surface
Meade County, SD 57 mi east · 3% at surface

What Lawrence County is built on

The largest mapped soluble unit here is the Madison Group (limestone), Mississippian to Devonian in age, covering about 19% of the county. Next is the Minnelusa Formation at 11%.

6% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

Against the rest of South Dakota

Lawrence County ranks 1 of 66 in South Dakota for soluble rock at the surface, and sits above 85% of US counties on that measure.