Sinkhole risk in Dauphin County, PA: 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: 9%
At or near the surface: 8%
Buried under cover: under 1%

What to do about a house in Dauphin County

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

That works out to roughly 45 of Dauphin County's 525 square miles on soluble rock, 44 of them with the rock at or near the surface. With about 293,029 residents (558 per square mile), most of the county is built up, so a mapped unit is likely to sit under somebody's street. The figures come from 599 map points about 0.9 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Dauphin County

The nearest county rated sinkhole country is Union County, PA, about 40 miles north. None of the 6 closest counties land in the same band, so Dauphin County stands out from its surroundings.

Lebanon County, PA 17 mi east · 31% at surface
Perry County, PA 25 mi west · 34% at surface
Snyder County, PA 28 mi northwest · 38% at surface
Cumberland County, PA 30 mi southwest · 48% at surface
Northumberland County, PA 31 mi north · 26% at surface
Juniata County, PA 33 mi west · 45% at surface

What Dauphin County is built on

The largest mapped soluble unit here is the Epler Formation (limestone), Ordovician in age, covering about 2% of the county. Next is the Limestone of Hamburg sequence at 2%.

Against the rest of Pennsylvania

Dauphin County ranks 32 of 67 in Pennsylvania for soluble rock at the surface, and sits above 66% of US counties on that measure.