Helena, Mont. — Montana homeowners face a very low risk of sinkholes, with experts saying true sinkhole formation is rare across most of the state.
According to the U.S. Geological Survey, Montana does not contain widespread limestone or other highly soluble rock formations typically associated with sinkhole development. As a result, naturally occurring sinkholes are uncommon and generally limited to isolated geological settings rather than broad regions.
Geologists note that while sinkholes are rare in Montana, ground-related problems can still occur for other reasons. Localized land subsidence, soil settling, or collapses tied to abandoned mines, underground voids, or erosion can sometimes be mistaken for sinkholes, even though the underlying cause is different.
True sinkholes, when they do occur, typically develop gradually. Experts emphasize that surface changes often provide early indicators of underground movement long before a collapse happens, even in states with very low sinkhole risk.
Homeowners who notice shallow depressions forming in yards, soil that feels unusually soft or spongy, or unexpected pooling water are encouraged to document those changes. Cracks appearing in sidewalks, driveways, patios, or foundation walls can also reflect subtle ground movement rather than routine settling, particularly if they worsen over time.
Other warning signs may be dismissed as normal wear. Leaning fences, separating steps, tilting trees, or gaps opening between soil and concrete surfaces can sometimes point to localized ground instability related to drainage or subsurface conditions.
In Montana, most ground changes are highly localized and often linked to mining history, soil composition, groundwater conditions, or development patterns rather than natural sinkhole processes. Experts stress that risk can vary by neighborhood depending on land use and subsurface conditions.
The USGS advises homeowners not to fill or cover unexplained depressions if changes persist or worsen, as doing so can hide underlying issues and delay proper evaluation by local officials or qualified professionals.
Experts stress that awareness — not alarm — remains the best approach. Even in states where sinkholes are rare, early attention to subtle ground changes can help prevent property damage and improve safety.
