Buried valley

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 predominantly gravel and sand, with some 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.

Buried valleys are created when ancient river or stream valleys are present that predate the most recent glaciation, and since have been filled with glacial till and/or outwash. In the , advancement and retreat of glaciers carved out the preexisting valleys, and deposited the material that had accumulated in the glacier by the melting of either the glacial outwash or the melting of the ice that composed the glacier itself. Buried valleys are traditionally V- or U-shaped due to the natural shape of valleys, but buried valleys can exhibit different shapes if there were any sort of erosional events after the glacier had finished retreating. The ability to hold groundwater comes from the makeup of the glacial outwash deposits. The glacial outwash deposits of these preexisting valleys mainly consist of coarser materials, such as sand and gravel. Since these materials are coarser, when there is a soil that is almost purely made of these materials, the pore space of the soil increases. This increased pore space creates more voids for water, especially when compared to silt or clay rich soil. After these valleys are formed and filled in, a layer of finer sediment such as silts and clays covers the top of the valley, burying the valley. Buried valleys are best known as being aquifers, and are often used to supply humans with potable water, as well as supply the agriculture and industrial fields with water.

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