Sinkhole risk in Smith County, MS: 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: 13%
At or near the surface: 13%
Buried under cover: 0%

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 85 of Smith County's 636 square miles on soluble rock, 85 of them with the rock at or near the surface. With about 14,051 residents (22 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 352 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Smith County

The nearest county rated sinkhole country is Noxubee County, MS, about 93 miles northeast. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Jasper County, MS 22 mi east · 21% at surface
Simpson County, MS 26 mi west · 0% at surface
Covington County, MS 27 mi south · 0% at surface
Scott County, MS 27 mi north · 7% at surface
Rankin County, MS 31 mi northwest · 13% at surface
Jones County, MS 34 mi southeast · under 1% at surface

Which formation it is

The largest mapped soluble unit here is the Vicksburg group and Chickasawhay limestone (limestone), Oligocene in age, covering about 13% of the county.

The county also lies over the Gulf Coast salt domes, 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 Mississippi

Smith County ranks 21 of 82 in Mississippi for soluble rock at the surface, and sits above 70% of US counties on that measure.