Sinkhole risk in Phelps 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 672 of Phelps County's 672 square miles on soluble rock, 672 of them with the rock at or near the surface. With about 45,672 residents (68 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 259 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Phelps County

The closest county with no soluble rock mapped is Clay County, AR, about 128 miles southeast. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Maries County, MO 22 mi north · 100% at surface
Pulaski County, MO 23 mi west · 100% at surface
Dent County, MO 25 mi southeast · 100% at surface
Crawford County, MO 27 mi east · 100% at surface
Texas County, MO 39 mi south · 100% at surface
Osage County, MO 41 mi north · 93% at surface

The rock underneath

The largest mapped soluble unit here is the Roubidoux Formation (sandstone), Early Ordovician-Ibexian Series in age, covering about 49% of the county. Next is the Gasconade Dolomite at 21%.

Against the rest of Missouri

Phelps County ranks 14 of 115 in Missouri for soluble rock at the surface, and sits above 99% of US counties on that measure.