SinkholeOdds

Sinkhole risk in Blaine County, OK: Sinkhole country

Sinkhole country

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

On soluble rock
55%
At or near the surface
55%
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 511 of Blaine County's 928 square miles on soluble rock, 511 of them with the rock at or near the surface. With about 8,573 residents (9 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 380 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Blaine County

The closest county with no soluble rock mapped is Logan County, OK, about 55 miles east. 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 Flowerpot Shale (shale), Early Permian in age, covering about 19% of the county. Next is the Rush Springs Formation at 14%.

55% 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

Blaine County ranks 10 of 77 in Oklahoma for soluble rock at the surface, and sits above 89% of US counties on that measure.