The most common and destructive landslides in the Cincinnati, Ohio, area are formed in colluvium. Colluvium is formed from bedrock units by weathering and slaking of shales. The principal colluviurn-producing bedrock unit is the Kope Formation, which occupies the lower 60-70 m of hillslopes between the level of the Ohio River and an upland some 150 m above the river level. This formation, which contains about 80 percent shale and 20 percent limestone, slakes readily to produce a stony, silty clay colluvium. Overlying formations contain smaller amounts of shale, typically produce smaller amounts of a more stone-rich colluvium, and support steeper slopes. The colluvium forms a wedgeshaped mass ranging up to about 15 m in thickness. In the upper parts of the slopes, grades are steeper and the colluvium is thinner.