Sinkhole risk in Freeborn County, MN: 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: 100%
At or near the surface: 0%
Buried under cover: 100%

What this means before you buy

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

That works out to roughly 707 of Freeborn County's 707 square miles on soluble rock. With about 30,314 residents (43 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 390 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 100% under cover still counts, and how these percentages are measured.

Counties around Freeborn County

The nearest county rated sinkhole country is Clayton County, IA, about 117 miles southeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Worth County, IA 21 mi south · 0% at surface
Steele County, MN 24 mi north · 0% at surface
Waseca County, MN 27 mi northwest · 0% at surface
Winnebago County, IA 28 mi southwest · 0% at surface
Mower County, MN 30 mi east · 0% at surface
Faribault County, MN 30 mi west · 0% at surface

What Freeborn County is built on

The largest mapped soluble unit here is the Devonian rocks, undivided (limestone), Devonian in age, covering about 65% of the county. Next is the Upper and Middle Ordovician rocks, undivided at 35%.

Against the rest of Minnesota

Freeborn County ranks 30 of 87 in Minnesota for soluble rock at the surface, and sits above 0% of US counties on that measure.