SinkholeOdds

Sinkhole risk in Roger Mills County, OK: Sinkhole country

Sinkhole country

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

On soluble rock
31%
At or near the surface
31%
Buried under cover
0%

What to do about a house in Roger Mills County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 353 of Roger Mills County's 1,141 square miles on soluble rock, 353 of them with the rock at or near the surface. With about 3,304 residents (3 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 307 map points about 1.9 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Roger Mills County

The closest county with no soluble rock mapped is Hemphill County, TX, about 31 miles west. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

The rock underneath

The largest mapped soluble unit here is the Cloud Chief Formation (shale), Late Permian in age, covering about 26% of the county. Next is the Rush Springs Formation at 5%.

31% 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

Roger Mills County ranks 29 of 77 in Oklahoma for soluble rock at the surface, and sits above 80% of US counties on that measure.