SinkholeOdds

Sinkhole risk in San Juan County, UT: 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
12%
At or near the surface
12%
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 954 of San Juan County's 7,824 square miles on soluble rock, 954 of them with the rock at or near the surface. With about 14,601 residents (2 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 246 map points about 5.6 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 San Juan County

The nearest county rated sinkhole country is Emery County, UT, about 109 miles northwest. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

The rock underneath

The largest mapped soluble unit here is the Triassic (1) sedimentary rocks in Salt southeastern Utah (mudstone), Early Triassic in age, covering about 6% of the county. Next is the Pennsylvanian and Permian sedimentary rocks in southeastern Utah at 4%.

9% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

The county also lies over the Paradox Basin, 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 Utah

San Juan County ranks 11 of 29 in Utah for soluble rock at the surface, and sits above 69% of US counties on that measure.