Sinkhole risk in Dallas County, MO: Sinkhole country

Sinkhole country

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

On soluble rock: 100%
At or near the surface: 100%
Buried under cover: 0%

The next step for one property

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

That works out to roughly 541 of Dallas County's 541 square miles on soluble rock, 541 of them with the rock at or near the surface. With about 17,877 residents (33 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 355 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Dallas County

The closest county with no soluble rock mapped is Johnson County, AR, about 148 miles south. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Polk County, MO 21 mi west · 97% at surface
Hickory County, MO 24 mi northwest · 92% at surface
Laclede County, MO 24 mi east · 100% at surface
Camden County, MO 28 mi northeast · 100% at surface
Webster County, MO 29 mi south · 100% at surface
Greene County, MO 34 mi southwest · 97% at surface

What Dallas County is built on

The largest mapped soluble unit here is the Smithville Dolomite, Powell Dolomite, Cotter Dolomite, Jefferson City Dolomite (dolostone (dolomite)), Early Ordovician-Ibexian Series in age, covering about 67% of the county. Next is the Roubidoux Formation at 21%.

Against the rest of Missouri

Dallas County ranks 3 of 115 in Missouri for soluble rock at the surface, and sits above 99% of US counties on that measure.