Sinkhole risk in Humboldt County, CA: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 3%
At or near the surface: 3%
Buried under cover: 0%

The next step for one property

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 93 of Humboldt County's 3,568 square miles on soluble rock, 93 of them with the rock at or near the surface. With about 132,380 residents (37 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 270 map points about 3.6 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Humboldt County

The nearest county rated sinkhole country is Emery County, UT, about 709 miles east. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Trinity County, CA 43 mi east · 25% at surface
Del Norte County, CA 72 mi north · under 1% at surface
Mendocino County, CA 92 mi south · 0% at surface
Siskiyou County, CA 95 mi northeast · 9% at surface
Tehama County, CA 98 mi southeast · 1% at surface
Shasta County, CA 99 mi east · 9% at surface

What Humboldt County is built on

The largest mapped soluble unit here is the Paleozoic marine rocks, undivided, unit 9 (Western Klamath Mountains) (argillite), Devonian to Jurassic in age, covering about 3% of the county.

Against the rest of California

Humboldt County ranks 11 of 58 in California for soluble rock at the surface, and sits above 59% of US counties on that measure.