- Tunnel valley
A tunnel valley is a deep but narrow
valleywith a 'U' shaped cross-section and frequently a 'U' shaped plan which is usually found filled with glacial till. It is formed when the edge of an ice sheet advances up a slope. Its length may be appropriately measured in centimetres or kilometres, depending on the circumstances of formation. The small ones are known as Nye channels (named after British physicist John Nye). The larger ones may be a hundred kilometres long and are known also as a rinnental or tunnel-dale.
They are found for example, in north
Germanywhere the thick ice sheet of the Weichsel and earlier Glaciations, having flowed down from the mountains of Scandinavia, began to rise up the north-European slope, driven by the altitude of its surface over Scandinavia. Their alignment indicates the direction of ice flow at the time of their formation.
The thickness of the ice means that melt water lying in
crevassescan have a head of perhaps hundreds of metres. This applies great hydrostatic pressure at the bottom of the ice where the melting is assisted by geothermal heat. Where at the ice margin, the land surface rises away from the ice, the water escapes with a helical flow and forms tunnels, partly in the ice and partly in the rock below. When the ice melts, the lower part of the tunnel remains but at this stage, is usually filled by till or the sediment in a Proglacial lake.
physicsof their formation means that they are frequently double, with two branches extending uphill to the former ice margin from a single seat of origin. The branches may have branched again before the open air was reached. They therefore give the impression of the effect of a normal river flow in the opposite direction.
Benn, D.I. & Evans, D.J.A. "Glaciers & Glaciation" (1998) ISBN 0-340-58431-9
Snake coils (geology)
Wikimedia Foundation. 2010.
Look at other dictionaries:
tunnel valley — A relatively shallow trench or depression cut into drift and other loose material, or in bedrock, by a subglacial stream not loaded with coarse sediment that may or may not be part of the present day drainage pattern. GG … Glossary of landform and geologic terms
tunnel-valley lake — A glacial lake occupying a portion of a tunnel valley. GG … Glossary of landform and geologic terms
Tunnel-Creek-Nationalpark — Höhleneingang … Deutsch Wikipedia
Tunnel Creek National Park — Höhleneingang … Deutsch Wikipedia
Tunnel View — Tunnel View, within Yosemite National Park, is a viewpoint on State Route 41 located directly east of the Wawona Tunnel as one enters Yosemite Valley from the South. The view looks east into Yosemite Valley including the southwest face of El… … Wikipedia
Valley Parade — Full name Coral Windows Stadium Location Bradford, West Yorkshire, England … Wikipedia
Valley of the Shadows — by Origin Unknown is a highly influential drum and bass track from 1993 released on Ram Records. Originally featured as a B side of the 4th Ram Records release Valley of the Shadows proved a lot more popular than the A side, The Touch , and the… … Wikipedia
Tunnel Hill, Ohio — Tunnel Hill is an unincorporated place in central Bedford Township, Coshocton County, Ohio, United States. It lies in the valley of the Little Wakatomika Creek a few miles south of Warsaw along State Route 60 at its intersection with State Route… … Wikipedia
Tunnel Mountain — Infobox Mountain Name = Tunnel Mountain Photo = Banff from Sulphur Mtn 2004.jpg Caption = Tunnel Mountain and Banff townsite, seen from Sulphur Mountain Elevation = m to ft|1692|abbr=yes|wiki=yes|precision=0cite web | last =Birrell | first =Dave… … Wikipedia
Tunnel — This article is about underground passages. For other uses, see Tunnel (disambiguation). Underground tunnel for heatpipes between Rigshospitalet and Amagerværket in Denmark … Wikipedia