Sinkhole risk in Montgomery 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: 46%
At or near the surface: 0%
Buried under cover: 46%

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 196 of Montgomery County's 424 square miles on soluble rock. With about 10,063 residents (24 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.

Worth reading for this county: why the 46% under cover still counts, and how these percentages are measured.

Counties around Montgomery County

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

Page County, IA 20 mi south · 0% at surface
Adams County, IA 24 mi east · 0% at surface
Mills County, IA 24 mi west · 0% at surface
Cass County, IA 25 mi northeast · 0% at surface
Pottawattamie County, IA 30 mi northwest · 0% at surface
Fremont County, IA 30 mi southwest · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Wabaunsee Group (shale), Late Pennsylvanian-Virgil Series in age, covering about 26% of the county. Next is the Shawnee Group at 19%.

Against the rest of Iowa

Montgomery County ranks 71 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.