Sinkhole risk in Jackson County, FL: Sinkhole country

Sinkhole country

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

On soluble rock: 100%
At or near the surface: 87%
Buried under cover: 13%

What to do about a house in Jackson County

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

Standard Florida homeowners policies cover only catastrophic ground cover collapse; full sinkhole coverage is a separately priced option insurers must offer.

That works out to roughly 918 of Jackson County's 918 square miles on soluble rock, 800 of them with the rock at or near the surface. With about 49,980 residents (54 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 278 map points about 1.8 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Jackson County

The closest county with no soluble rock mapped is Gulf County, FL, about 64 miles south. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Seminole County, GA 23 mi northeast · 86% at surface
Houston County, AL 26 mi north · 84% at surface
Calhoun County, FL 28 mi south · 13% at surface
Washington County, FL 30 mi southwest · 54% at surface
Holmes County, FL 36 mi west · 66% at surface
Decatur County, GA 38 mi east · 55% at surface

The rock underneath

The largest mapped soluble unit here is the Residuum on Oligocene sediments (limestone), Oligocene in age, covering about 18% of the county. Next is the Alum Bluff Group at 16%.

Against the rest of Florida

Jackson County ranks 7 of 67 in Florida for soluble rock at the surface, and sits above 96% of US counties on that measure.