Fold mountains are mountains formed mainly by the effects of folding on layers in the upper part of the Earth's crust. The term is rather out of date, though still fairly common in physical geography literature.
In the time before plate tectonics became well understood, the term was used for most mountain belts, such as the Himalayas. These mountain ranges are not caused by the folding of the earth's crust. The main mechanism causing a thickening of the crust at these sites of continent-continent collision along a convergent boundary is thrust faulting.
Fold mountains are formed when two tectonic plates move together (a convergent plate boundary). Fold mountains are usually formed from sedimentary rocks which accumulated along the margins of continents. When plates and the continents riding on them collide, the accumulated layers of rock may crumple and fold like a tablecloth that is pushed across a table, particularly if there is a mechanically weak basal layer such as salt.
Examples[change | edit source]
- The Jura mountains – a series of sub-parallel mountainous ridges formed by folding over a Triassic evaporite decollement due to thrust movements in the foreland of the Alps.
- The 'Simply Folded Belt' of the Zagros mountains – here both thrusts and fold are occurring.
- The Akwapim-Togo ranges in Ghana
- part of the Appalachans in the Eastern United States, known as the "Ridge-and-Valley Appalachians".
Related pages[change | edit source]
References[change | edit source]
- Ulmer, S. (11 August 2011). "Fold mountains slip on soft areas". ETH Life. ETH Zürich. http://www.ethlife.ethz.ch/archive_articles/110811_gebirgsbildung_su/index_EN. Retrieved 21 February 2012.