One of Ontario's most striking geological formations, this cuesta has at its base granite rocks formed deep in the Earth some 2,500,000,000 years ago and exposed after millions of years of erosion. Subsequently, a thick deposit of sediment accumulated, possibly in the waters of an inland sea that once covered this region. The sediment was converted by pressure into layers of shale, impure limestone and sandstone, red in colour owing to the presence of iron-bearing hematite. A molten material, diabase, later forced its way horizontally between the sediments, forming a "sill," which was uncovered by subsequent erosion. This is the dark rock capping the hill. Its columnar structure was produced by shrinkage during the cooling process.

Location

Near the Red Rock Interpretive Centre

Themes

• Environment