Sinkhole risk in Delaware County, OK: Sinkhole country

Sinkhole country

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

On soluble rock: 94%
At or near the surface: 94%
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 696 of Delaware County's 738 square miles on soluble rock, 696 of them with the rock at or near the surface. With about 41,771 residents (57 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 360 map points about 1.4 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 Delaware County

The closest county with no soluble rock mapped is Crawford County, AR, about 64 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Mayes County, OK 25 mi west · 48% at surface
McDonald County, MO 30 mi northeast · 100% at surface
Ottawa County, OK 31 mi north · 63% at surface
Benton County, AR 31 mi east · 93% at surface
Craig County, OK 34 mi northwest · 31% at surface
Adair County, OK 35 mi south · 79% at surface

Which formation it is

The largest mapped soluble unit here is the Keokuk and Reeds Spring Formations and St. Joe Group (chert), Early Mississippian in age, covering about 89% of the county. Next is the Pitkin + Fayetteville + Batesville + Hindsville + Moorefield Formations at 3%.

Against the rest of Oklahoma

Delaware County ranks 1 of 77 in Oklahoma for soluble rock at the surface, and sits above 98% of US counties on that measure.