Sinkhole risk in Charlotte County, FL: Sinkhole country

Sinkhole country

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

On soluble rock: 85%
At or near the surface: 81%
Buried under cover: 4%

What this means before you buy

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 580 of Charlotte County's 681 square miles on soluble rock, 553 of them with the rock at or near the surface. With about 212,122 residents (311 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 351 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Charlotte County

The closest county with no soluble rock mapped is Gulf County, FL, about 285 miles northwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

DeSoto County, FL 23 mi northeast · 73% at surface
Lee County, FL 24 mi south · 69% at surface
Sarasota County, FL 34 mi northwest · 83% at surface
Hardee County, FL 42 mi north · 32% at surface
Manatee County, FL 46 mi northwest · 41% at surface
Glades County, FL 50 mi east · 69% at surface

Which formation it is

The largest mapped soluble unit here is the Shelly sediments of Plio-Pleistocene age (limestone), Pliocene/Pleistocene in age, covering about 80% of the county. Next is the Shelly sediments of Plio-Pleistocene age at 4%.

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 Florida

Charlotte County ranks 12 of 67 in Florida for soluble rock at the surface, and sits above 95% of US counties on that measure.