A buried valley is an ancient river or stream valley that has been filled with glacial or unconsolidated sediment. This sediment is made up of gravel, sand, silt, and clay. These types of sediments can often store and transmit large amounts of groundwater and act as a local aquifer.
Buried valleys may have been created by glacial lake runoff prior to the last major advance and retreat of continental glaciation. These valleys often have no surface expression, but constitute a major source of groundwater in the glaciated mid-continent region of North America and Northern Europe. Recently, research has been focused on understanding the sedimentology of these formations in an effort to determine the safety of continued use of the aquifers which are often found in them.