Sinkhole risk in Penobscot County, ME: 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: 8%
At or near the surface: 0%
Buried under cover: 8%

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 265 of Penobscot County's 3,397 square miles on soluble rock. With about 156,840 residents (46 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 438 map points about 2.8 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 8% under cover still counts, and how these percentages are measured.

Counties around Penobscot County

The nearest county rated sinkhole country is Union County, PA, about 522 miles southwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Piscataquis County, ME 41 mi northwest · under 1% at surface
Washington County, ME 60 mi southeast · 0% at surface
Hancock County, ME 60 mi south · 0% at surface
Somerset County, ME 63 mi west · 0% at surface
Waldo County, ME 68 mi south · 0% at surface
Kennebec County, ME 87 mi southwest · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Silurian unnamed limestone (limestone), Silurian in age, covering about 3% of the county. Next is the Devonian - Ordovician Bucksport Formation at 2%.

Against the rest of Maine

Penobscot County ranks 11 of 16 in Maine for soluble rock at the surface, and sits above 0% of US counties on that measure.