Sinkhole risk in Gasconade County, MO: Sinkhole country

Sinkhole country

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

On soluble rock: 99%
At or near the surface: 97%
Buried under cover: 3%

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 516 of Gasconade County's 519 square miles on soluble rock, 503 of them with the rock at or near the surface. With about 14,655 residents (28 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 362 map points about 1.2 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 Gasconade County

The closest county with no soluble rock mapped is Macoupin County, IL, about 102 miles northeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Osage County, MO 19 mi west · 93% at surface
Franklin County, MO 24 mi east · 96% at surface
Warren County, MO 29 mi northeast · 42% at surface
Maries County, MO 30 mi southwest · 100% at surface
Montgomery County, MO 34 mi north · 30% at surface
Crawford County, MO 34 mi south · 100% at surface

The rock underneath

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 41% of the county. Next is the Pennsylvanian Undifferentiated at 41%.

Against the rest of Missouri

Gasconade County ranks 30 of 115 in Missouri for soluble rock at the surface, and sits above 98% of US counties on that measure.