Sinkhole risk in Osage County, MO: Sinkhole country

Sinkhole country

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

On soluble rock: 96%
At or near the surface: 93%
Buried under cover: 4%

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 583 of Osage County's 607 square miles on soluble rock, 562 of them with the rock at or near the surface. With about 13,478 residents (22 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 284 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Osage County

The closest county with no soluble rock mapped is Macoupin County, IL, about 118 miles northeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Gasconade County, MO 19 mi east · 97% at surface
Maries County, MO 21 mi south · 100% at surface
Cole County, MO 23 mi west · 94% at surface
Callaway County, MO 26 mi north · 28% at surface
Miller County, MO 35 mi southwest · 100% at surface
Montgomery County, MO 39 mi northeast · 30% at surface

What Osage 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 53% of the county. Next is the Pennsylvanian Undifferentiated at 22%.

Against the rest of Missouri

Osage County ranks 38 of 115 in Missouri for soluble rock at the surface, and sits above 97% of US counties on that measure.