Fault-block landforms are formed when large areas of bedrock are widely broken up by faults creating large vertical displacements of continental crust.
Vertical motion of the resulting blocks, sometimes accompanied by tilting, can then lead to high
escarpmentAn escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
s. These mountains are formed by the Earth's crust being stretched and extended by tensional forces. Fault block mountains commonly accompany
riftIn geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ing, another indicator of tensional tectonic forces.
The uplifted blocks are called
block mountains or
horsts. The intervening dropped blocks are termed
grabenIn geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
: these can be small or form extensive
rift valleyA rift valley is a linear-shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault. This action is manifest as crustal extension, a spreading apart of the surface which is subsequently further deepened by the forces of erosion...
systems. This form of
landscapeLandscape comprises the visible features of an area of land, including the physical elements of landforms such as mountains, hills, water bodies such as rivers, lakes, ponds and the sea, living elements of land cover including indigenous vegetation, human elements including different forms of...
can be seen in
East AfricaEast Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
, the
VosgesVosges is a French department, named after the local mountain range. It contains the hometown of Joan of Arc, Domrémy.-History:The Vosges department is one of the original 83 departments of France, created on February 9, 1790 during the French Revolution. It was made of territories that had been...
, the
Basin and RangeThe Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins...
province of Western
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, in south-central
New EnglandNew England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
, and the
Rhine valley. These areas often occur when the regional stress is extensional and the
crustIn geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
is thinned.
Two types of block mountains are lifted and tilted. Tilted type block mountains have one gently sloping side and one steep side with an exposed scarp, and are common in the
Basin and RangeThe Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins...
region of the western
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Level blocks lead to the
horst and
grabenIn geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
terrain seen in northern
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Lifted type block mountains have two steep sides exposing both sides scarps.
See also
- List of mountain types
- Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
- Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
- Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
- Mountain building
External links
- http://www.universetoday.com/guide-to-space/earth/fault-block-mountains/
- http://science.jrank.org/pages/2667/Fault-Mountain-building-by-small-movements-along-faults.html Fault - Mountain-building By Small Movements Along Faults