Other Geologic Hazards

windblown deposits
Windblown deposits. [Credit: Seth Wittke, WSGS]

Windblown Deposits

Windblown deposits form when sand, silt, or clay materials are transported by wind and deposited on the ground surface. Most windblown deposits are not damaging, but they are considered a geologic hazard because they have the potential to cause adverse impacts when they encroach on infrastructure, roads, and agricultural lands.

Windblown deposits occur in many parts of Wyoming. Active windblown deposits are found in the Killpecker Dune Field in Sweetwater County, the Seminoe Dune Fields in Carbon County, and the Casper Dune Field in Natrona County. The majority of windblown deposits in the state are stabilized by vegetation. While such inactive windblown deposits do not pose a hazard in their present state, they may mobilize and become active again if they are disturbed by development and not properly stabilized.

Expansive Soils

Various geologic units in Wyoming contain, or can weather to produce, shrink-swell clays. Changes in moisture cause these clay minerals to expand and contract, often resulting in large volumetric changes in the soil. If structures or roads are built on these soils without proper mitigation procedures, the expansion and contraction of the soil can cause cracking, collapse, or failure.

The most common shrink-swell clays in Wyoming are sodium montmorillonite (also known as bentonite) and calcium montmorillonite. These minerals are most commonly found in Cretaceous shales and volcanic ash deposits.

The Wyoming Geologic Hazards Map provides the locations of geologic formations with known or suspected expansive soil hazards.

expansive soils diagram
The potential for a rock/soil to swell depends on its mineralogy, but actual swelling is caused by a change in the environment surrounding the material. [Credit: Modified from the Wyoming Multi-Hazard Mitigation Plan]


James Mauch, james.mauch@wyo.gov