Sinkhole risk in Norfolk County, MA: 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: 1%
At or near the surface: 0%
Buried under cover: 1%

The next step for one property

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

That works out to roughly 6 of Norfolk County's 396 square miles on soluble rock. With about 740,754 residents (1,870 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 486 map points about 0.9 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 Norfolk County

The nearest county rated sinkhole country is Union County, PA, about 315 miles west. None of the 6 closest counties land in the same band, so Norfolk County stands out from its surroundings.

Suffolk County, MA 14 mi northeast · 0% at surface
Middlesex County, MA 24 mi northwest · 0% at surface
Plymouth County, MA 26 mi southeast · 0% at surface
Providence County, RI 29 mi southwest · 0% at surface
Bristol County, MA 30 mi south · 0% at surface
Bristol County, RI 33 mi south · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Braintree Argillite and Weymouth Formation (argillite), Middle and Lower Cambrian in age, covering about 1% of the county.

Against the rest of Massachusetts

Norfolk County ranks 11 of 14 in Massachusetts for soluble rock at the surface, and sits above 0% of US counties on that measure.