SinkholeOdds

Sinkhole risk in Dewey County, OK: Sinkhole country

Sinkhole country

Fast-dissolving gypsum or salt beds under a large part of the county.

On soluble rock
57%
At or near the surface
57%
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 567 of Dewey County's 1,000 square miles on soluble rock, 567 of them with the rock at or near the surface. With about 4,268 residents (4 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 406 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Dewey County

The closest county with no soluble rock mapped is Hemphill County, TX, about 72 miles west. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Which formation it is

The largest mapped soluble unit here is the Rush Springs Formation (sandstone), Early Permian in age, covering about 39% of the county. Next is the Cloud Chief Formation at 15%.

57% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

The county also lies over the Permian Basin, Anadarko Basin,Dalhart Basin, Palo Duro Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Oklahoma

Dewey County ranks 9 of 77 in Oklahoma for soluble rock at the surface, and sits above 89% of US counties on that measure.