The document discusses the distribution and thickness of volcanic and glacial cover on the Interior Plateaus of south-central British Columbia. The Chilcotin Group volcanic rocks cover over 35,500 km2 but their thickness and distribution are poorly constrained. Recent research indicates the volcanic rocks have extreme thickness variations from 0-100 meters, forming paleo-drainage channels and leaving many "basement windows" exposed. This challenges the previous assumption of a homogeneous thick sheet and greatly reduces the mapped areal extent of the volcanic rocks. Identifying these paleo-drainage systems could have implications for regional mineral exploration methods.