LOUDERBACK

a fault block that is gently tilted (usually 15 degrees or less) and is capped by a lava flow. These slopes are especially evident wherever lavas, resistant to erosion in dry climates, flowed onto the surfaces before they were tilted. Louderbacks are common in the Basin and Range Province (occupying almost all of Nevada, the western half of Utah, southeastern California, and the southern part of Arizona, as well as northwestern Mexico), where they are used for relative dating of the strata and faulting. Occasionally the surrounding area is greatly eroded, leaving the louderbacks as relatively flat-topped mesas.