Sinkhole risk in Franklin 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: 4%
At or near the surface: 0%
Buried under cover: 4%

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 71 of Franklin County's 1,697 square miles on soluble rock. With about 30,902 residents (18 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 475 map points about 1.9 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Franklin County

The nearest county rated sinkhole country is Union County, PA, about 435 miles southwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Oxford County, ME 37 mi southwest · 0% at surface
Somerset County, ME 43 mi northeast · 0% at surface
Coos County, NH 48 mi southwest · 0% at surface
Kennebec County, ME 50 mi southeast · 0% at surface
Androscoggin County, ME 57 mi south · 0% at surface
Essex County, VT 67 mi west · 0% at surface

What Franklin County is built on

The largest mapped soluble unit here is the Silurian Sangerville Formation Anasagunticook member (metasedimentary rock), Silurian in age, covering about 3% of the county. Next is the Devonian Hildreths Formation at under 1%.

Against the rest of Maine

Franklin County ranks 7 of 16 in Maine for soluble rock at the surface, and sits above 0% of US counties on that measure.