Sinkhole risk in Broadwater County, MT: Pockets of it
Pockets of it
Soluble rock at the surface or under thin cover in part of the county.
- On soluble rock
- 27%
- At or near the surface
- 27%
- Buried under cover
- 0%
What to do about a house in Broadwater County
Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.
That works out to roughly 321 of Broadwater County's 1,192 square miles on soluble rock, 321 of them with the rock at or near the surface. With about 8,302 residents (7 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 546 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.
Read next: the signs to look for and how an inspection works, and how these percentages are measured.
Counties around Broadwater County
The nearest county rated sinkhole country is Fall River County, SD, about 446 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.
- Jefferson County, MT 30 mi southwest · 6% at surface
- Meagher County, MT 33 mi northeast · 49% at surface
- Gallatin County, MT 58 mi south · 18% at surface
- Silver Bow County, MT 63 mi southwest · 10% at surface
- Cascade County, MT 69 mi north · 18% at surface
- Lewis and Clark County, MT 69 mi northwest · 25% at surface
Which formation it is
The largest mapped soluble unit here is the Newland limestone (carbonate), Middle-Proterozoic in age, covering about 18% of the county. Next is the Cambrian, undifferentiated at 4%.
Against the rest of Montana
Broadwater County ranks 5 of 56 in Montana for soluble rock at the surface, and sits above 78% of US counties on that measure.
- Meagher County 49%
- Mineral County 37%
- Judith Basin County 33%
- Lincoln County 29%
- Lewis and Clark County 25%