Sinkhole risk in Oregon 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%

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 790 of Oregon County's 790 square miles on soluble rock, 790 of them with the rock at or near the surface. With about 8,699 residents (11 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 390 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Oregon County

The closest county with no soluble rock mapped is Clay County, AR, about 59 miles east. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Howell County, MO 28 mi west · 100% at surface
Ripley County, MO 29 mi east · 95% at surface
Carter County, MO 31 mi northeast · 100% at surface
Fulton County, AR 31 mi southwest · 100% at surface
Randolph County, AR 32 mi southeast · 60% at surface
Shannon County, MO 32 mi north · 99% at surface

Which formation it is

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 59% of the county. Next is the Roubidoux Formation at 37%.

Against the rest of Missouri

Oregon County ranks 12 of 115 in Missouri for soluble rock at the surface, and sits above 99% of US counties on that measure.