Sinkhole risk in Johnson County, MO: Sinkhole country

Sinkhole country

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

On soluble rock: 50%
At or near the surface: 50%
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 415 of Johnson County's 829 square miles on soluble rock, 415 of them with the rock at or near the surface. With about 55,880 residents (67 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 384 map points about 1.5 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 Johnson County

The closest county with no soluble rock mapped is Putnam County, MO, about 127 miles north. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lafayette County, MO 23 mi north · 32% at surface
Henry County, MO 25 mi south · 18% at surface
Pettis County, MO 28 mi east · 71% at surface
Cass County, MO 30 mi west · 72% at surface
Jackson County, MO 34 mi northwest · 71% at surface
Ray County, MO 40 mi north · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Marmaton Group (limestone), Middle Pennsylvanian-Middle Series-Desmonian Stage in age, covering about 48% of the county. Next is the Kansas City Group at 2%.

Against the rest of Missouri

Johnson County ranks 56 of 115 in Missouri for soluble rock at the surface, and sits above 87% of US counties on that measure.