Sinkhole risk in Glynn County, GA: 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 to do about a house in Glynn County

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

That works out to roughly 34 of Glynn County's 420 square miles on soluble rock. With about 86,540 residents (206 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 511 map points about 0.9 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and why the 8% under cover still counts.

Counties around Glynn County

The nearest county rated sinkhole country is Nassau County, FL, about 45 miles south. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

McIntosh County, GA 20 mi north · 0% at surface
Camden County, GA 22 mi southwest · under 1% at surface
Brantley County, GA 29 mi west · under 1% at surface
Wayne County, GA 34 mi northwest · 0% at surface
Long County, GA 40 mi north · 0% at surface
Liberty County, GA 41 mi north · 0% at surface

What Glynn County is built on

The largest mapped soluble unit here is the Charlton Formation and Duplin Marl (limestone), Pliocene in age, covering about 8% of the county.

The county also lies over the Floridan shelf, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Georgia

Glynn County ranks 103 of 159 in Georgia for soluble rock at the surface, and sits above 0% of US counties on that measure.