Sinkhole risk in Frederick County, MD: 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: 13%
At or near the surface: 13%
Buried under cover: 0%

What to do about a house in Frederick County

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

That works out to roughly 87 of Frederick County's 661 square miles on soluble rock, 87 of them with the rock at or near the surface. With about 299,317 residents (453 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 258 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Frederick County

The nearest county rated sinkhole country is Washington County, MD, about 24 miles northwest, close enough that the same rock may run under the county line. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Carroll County, MD 21 mi east · 2% at surface
Washington County, MD 24 mi northwest · 61% at surface
Montgomery County, MD 25 mi southeast · 0% at surface
Jefferson County, WV 27 mi southwest · 84% at surface
Adams County, PA 29 mi north · 6% at surface
Howard County, MD 29 mi southeast · under 1% at surface

Which formation it is

The largest mapped soluble unit here is the Frederick Limestone (limestone), Cambrian in age, covering about 9% of the county. Next is the Grove Limestone at 3%.

Against the rest of Maryland

Frederick County ranks 8 of 24 in Maryland for soluble rock at the surface, and sits above 70% of US counties on that measure.