Subscribe to Updates
Greater Cincinnati’s Unstable Geology
Between 12,000 years and two million years ago, glaciers covered what we now identify as the Greater Cincinnati region, including Northern Kentucky, Southwestern Ohio, and Southeastern Indiana.
These glaciers dammed north-flowing streams resulting in massive lakes that collected fine layers of silt and clay (lake clays). When the glaciers receded, we were left with our present-day landscape that includes numerous hillsides and valleys.
The majority of Greater Cincinnati’s hillsides consist of an underlying layer of bedrock approximately 200 feet thick, made up of 80% shale and 20% limestone. When shale is exposed to air and water, it quickly breaks down into an unstable material known as colluvium.
Colluvium can range from several feet to 50 feet in thickness, and it is highly susceptible to erosion and landsliding. Some of the region’s valleys contain lake clays. These clays are associated with landslides that can occur on the gentlest of slopes.
The instability of Greater Cincinnati’s hillsides becomes more problematic due to excessive periods of precipitation, and construction methods that fail to address the underlying geology.
Annually, the Greater Cincinnati region experiences millions of dollars in damages from landsliding, making it one of the more landslide susceptible areas in the country.
To learn more, click the button below to download our Landslide Brochure.
Although technically not a landslide, creep is a process of soil (less than 18 inches thick) moving downslope under the influence of gravity. Signs include curved tree trunks, tilted utility poles, and leaning walls. Creep may be a precursor to a landslide or be underlain by an existing landslide. Careful examination is needed by a geologist or geotechnical engineer to differentiate between landsliding and creep.
Occurs at a depth of 6 feet or less, where a solid sheet of ground has moved downhill after becoming too wet and unable to hold itself in place. Movement can be rapid. Often the bedrock layer is exposed at the top of the slide. Costs can range from moderate to expensive for cleanup, stabilization, and prevention of future slides.
Occurs at a depth greater than 6 feet, where the ground has moved downhill along a concave (or bowl-shaped) surface. At the bottom of the landslide, material has rotated up and out in the form of a hump or bulge. At the top of the slide, a scarp may be exposed and the ground may be sunken. These landslides are difficult to stabilize and expensive to remediate.