Sinkhole risk in Los Angeles 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: 1%
At or near the surface: 1%
Buried under cover: 0%

What to do about a house in Los Angeles County

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

That works out to roughly 49 of Los Angeles County's 4,060 square miles on soluble rock, 49 of them with the rock at or near the surface. With about 9,757,179 residents (2,403 per square mile), most of the county is built up, so a mapped unit is likely to sit under somebody's street. The figures come from 410 map points about 3.1 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Los Angeles County

The nearest county rated sinkhole country is Emery County, UT, about 534 miles northeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Orange County, CA 45 mi southeast · 6% at surface
Ventura County, CA 51 mi west · 9% at surface
Kern County, CA 84 mi north · under 1% at surface
Santa Barbara County, CA 104 mi west · 3% at surface
San Diego County, CA 118 mi southeast · 0% at surface
San Bernardino County, CA 127 mi east · 2% at surface

What Los Angeles County is built on

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 1% of the county.

1% 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

Los Angeles County ranks 16 of 58 in California for soluble rock at the surface, and sits above 56% of US counties on that measure.