Sinkhole risk in Hamilton County, KS: 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: 5%
At or near the surface: 5%
Buried under cover: 0%

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 45 of Hamilton County's 997 square miles on soluble rock, 45 of them with the rock at or near the surface. With about 2,488 residents (2 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 382 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Hamilton County

The nearest county rated sinkhole country is Clark County, KS, about 120 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Kearny County, KS 26 mi east · 2% at surface
Stanton County, KS 30 mi south · 3% at surface
Prowers County, CO 33 mi west · 35% at surface
Greeley County, KS 34 mi north · 7% at surface
Grant County, KS 41 mi southeast · 0% at surface
Wichita County, KS 41 mi northeast · 13% at surface

What Hamilton County is built on

The largest mapped soluble unit here is the Greenhorn Limestone and Graneros Shale (limestone), Late Cretaceous in age, covering about 2% of the county. Next is the Ogallala Formation at 1%.

The county also lies over the Permian Basin, Anadarko Basin,Dalhart Basin, Palo Duro Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Kansas

Hamilton County ranks 81 of 105 in Kansas for soluble rock at the surface, and sits above 62% of US counties on that measure.