The top of the bedrock is known as the rockhead and identifying this, via excavations, drilling or geophysical methods, is an important task in most civil engineering projects. Loose material on top (known as drift) can be extremely thick, so that the bedrock lies hundreds of meters below the surface.
- "Swinford,E.Mac What the glaciers left behind - drift thickness map of Ohio, Ohio Department of Natural Resources, Division of Geological Survey, newsletter 2004, No.1" (PDF). Archived from the original (PDF) on 2012-10-02. Retrieved 2012-09-12.
- BGS. "Digital Geology - Bedrock geology theme". Archived from the original on 13 December 2009. Retrieved 2009-11-12.