SinkholeOdds

Sinkhole risk in Malheur County, OR: Not karst, but voids possible

Not karst, but voids possible

No soluble bedrock; some pseudokarst (piping or lava-tube ground).

On soluble rock
under 1%
At or near the surface
under 1%
Buried under cover
0%

The next step for one property

Not true karst, but soil piping or lava tubes can still open voids - mention it to an inspector.

That works out to roughly 89 of Malheur County's 9,888 square miles on soluble rock, 89 of them with the rock at or near the surface. With about 32,315 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 343 map points about 5.4 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how ground with no limestone still opens up, and how these percentages are measured.

Counties around Malheur County

The nearest county rated sinkhole country is Emery County, UT, about 460 miles southeast. 4 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 Sedimentary and volcanic rocks (Jurassic and Upper Triassic?) (graywacke), Late Triassic? to Jurassic in age, covering about under 1% of the county. Next is the Tuffaceous sedimentary rocks and tuff (Pliocene and Miocene) at under 1%.

Against the rest of Oregon

Malheur County ranks 9 of 36 in Oregon for soluble rock at the surface, and sits above 55% of US counties on that measure.