Sinkhole risk in Martin County, NC: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 84%
At or near the surface: 84%
Buried under cover: 0%

What to do about a house in Martin County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 385 of Martin County's 456 square miles on soluble rock, 385 of them with the rock at or near the surface. With about 21,523 residents (47 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 462 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Martin County

The closest county with no soluble rock mapped is Tyrrell County, NC, about 53 miles east. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Bertie County, NC 17 mi northeast · 68% at surface
Pitt County, NC 23 mi southwest · 86% at surface
Edgecombe County, NC 27 mi west · 62% at surface
Beaufort County, NC 30 mi southeast · 41% at surface
Washington County, NC 31 mi east · 11% at surface
Chowan County, NC 35 mi northeast · 15% at surface

Which formation it is

The largest mapped soluble unit here is the Yorktown Formation and Duplin Formation, Undivided (clay or mud), Tertiary in age, covering about 84% of the county.

Against the rest of North Carolina

Martin County ranks 7 of 100 in North Carolina for soluble rock at the surface, and sits above 95% of US counties on that measure.