Sinkhole risk in Humboldt County, IA: 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: 50%
At or near the surface: 0%
Buried under cover: 50%

What to do about a house in Humboldt County

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

That works out to roughly 219 of Humboldt County's 434 square miles on soluble rock. With about 9,617 residents (22 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 405 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 50% under cover still counts, and how these percentages are measured.

Counties around Humboldt County

The nearest county rated sinkhole country is Clayton County, IA, about 146 miles east. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Wright County, IA 24 mi east · 0% at surface
Webster County, IA 24 mi south · 0% at surface
Pocahontas County, IA 24 mi west · 0% at surface
Kossuth County, IA 30 mi north · 0% at surface
Hancock County, IA 31 mi northeast · 0% at surface
Palo Alto County, IA 31 mi northwest · 0% at surface

What Humboldt County is built on

The largest mapped soluble unit here is the Kinderhook Series (limestone), Early Mississippian in age, covering about 25% of the county. Next is the Meramec Series at 24%.

Against the rest of Iowa

Humboldt County ranks 51 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.