Nappe

In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than 2 km (1.2 mi) or 5 km (3.1 mi) above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the overriding plate in active subduction zones. Nappes form when a mass of rock is forced (or "thrust") over another rock mass, typically on a low angle fault plane. The resulting structure may include large-scale recumbent folds, shearing along the fault plane, imbricate thrust stacks, fensters and klippe.

The term stems from the French word for tablecloth in allusion to a crumpled tablecloth being pushed across a table.

History

Nappes or nappe belts are a major feature of the European Alps, Carpathians and Balkans. Since the 19th century many geologists have uncovered areas with large-scale overthrusts. Some of these were substantiated with paleontological evidence. The concept was developed by M.A. Bertrand, who unraveled the complex tectonic history of the Alps and identified the feature as nappe de charriage. He reinterpreted earlier studies by Escher and Heim in the Glarus Alps. His work in Switzerland influenced A. Escher von der Linth and M. Lugeon. Several years later, nappe structure was investigated in northwestern Scotland by Ch. Lapworth. Lugeon later transferred the ideas of nappes to the Carpathians.

Nappe (disambiguation)

In geology a nappe is a complex recumbent fold system.

In geometry, a nappe is half of a double cone.

In engineering a nappe can also refer to a sheet of water flowing over a dam or similar structure.

In cooking, nappe refers to either the ability of a liquid to "coat the back of a spoon" or the act of coating a food (i.e. to nappe a leg of lamb with glaze).

Nappe (water)

The term Nappe when used in relation to hydro-engineering refers to the sheet of water over-topping a dam. It is an important issue in dam construction because unless air can be introduced into the nappe, the vibration of the water can lead to dam failure.

Nappe vibration can be managed by flow splitters in the dam wall design.

Nappe- The underside of which is not in contact with the overflow of structure and is at ambient atmospheric pressure.

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