Sinkhole risk in Santa Barbara County, CA: 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: 3%
At or near the surface: 3%
Buried under cover: 0%

What this means before you buy

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

That works out to roughly 74 of Santa Barbara County's 2,734 square miles on soluble rock, 74 of them with the rock at or near the surface. With about 444,500 residents (163 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 486 map points about 2.4 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 how these percentages are measured.

Counties around Santa Barbara County

The nearest county rated sinkhole country is Emery County, UT, about 601 miles northeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Ventura County, CA 53 mi east · 9% at surface
San Luis Obispo County, CA 63 mi north · under 1% at surface
Kern County, CA 93 mi northeast · under 1% at surface
Los Angeles County, CA 104 mi east · 1% at surface
Kings County, CA 107 mi north · 0% at surface
Tulare County, CA 137 mi northeast · 3% at surface

The rock underneath

The largest mapped soluble unit here is the Oligocene nonmarine rocks, unit 2 (Central and Southern California) (sandstone), middle Eocene to early Miocene in age, covering about 3% of the county.

3% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

Against the rest of California

Santa Barbara County ranks 10 of 58 in California for soluble rock at the surface, and sits above 59% of US counties on that measure.