Sinkhole risk in Lancaster County, PA: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 46%
At or near the surface: 46%
Buried under cover: 0%

What this means before you buy

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 432 of Lancaster County's 944 square miles on soluble rock, 432 of them with the rock at or near the surface. With about 563,293 residents (597 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 552 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Lancaster County

The nearest county rated sinkhole country is Union County, PA, about 76 miles northwest. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lebanon County, PA 25 mi northwest · 31% at surface
York County, PA 27 mi west · 10% at surface
Chester County, PA 27 mi east · 7% at surface
Berks County, PA 31 mi northeast · 22% at surface
Harford County, MD 35 mi south · under 1% at surface
Cecil County, MD 37 mi southeast · 0% at surface

What Lancaster County is built on

The largest mapped soluble unit here is the Conestoga Formation (limestone), Ordovician and Cambrian in age, covering about 13% of the county. Next is the Ledger Formation at 7%.

Against the rest of Pennsylvania

Lancaster County ranks 3 of 67 in Pennsylvania for soluble rock at the surface, and sits above 86% of US counties on that measure.