geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

, horst and graben (or range and valley) refers to topography consisting of alternating raised and lowered

fault block Fault blocks are very large blocks of rock, sometimes hundreds of kilometres in extent, created by tectonic and localized stresses in Earth's crust. Large areas of bedrock are broken up into blocks by faults. Blocks are characterized by rela ...

s known as horsts and

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

s. The features are created by normal faulting and

rifting In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben ...

caused by crustal extension. Horst and graben are formed when normal faults of opposite dip occur in pairs with parallel

strike Strike may refer to: People * Strike (surname) Physical confrontation or removal *Strike (attack), attack with an inanimate object or a part of the human body intended to cause harm *Airstrike, military strike by air forces on either a suspected ...

, and are always formed together. Each feature can range in size from a few centimeters up to tens of kilometers, and the vertical displacement can be up to several thousand meters. The movement on either side of each block is typically equal, resulting in little tilting.

Features

Horst

A horst is a section of crust that has been lifted relative to the blocks on either side, which is a result of its bounding faults dipping away from each other. Horsts can form features such as plateaus, mountain ranges or ridges on either side of the valleys.

Graben

A graben is a section of crust that has lowered relative to the blocks on either side, which is a result of its bounding faults dipping towards each other. The plural of graben can be either graben or grabens. Graben form low-lying features such as basins and rift valleys. They can be very long relative to their width.

Examples

* The

Basin and Range Province The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...

in the western United States is an extensive region of alternating valleys and ridges caused by horst and graben as well as

tilted block faulting Tilted block faulting, also called rotational block faulting, is a mode of structural evolution in extensional tectonic events, a result of tectonic plates stretching apart. When the upper lithospheric crust experiences extensional pressures, t ...

. * The

Condroz The Condroz () is a natural region in Wallonia (the French-speaking part of Belgium), located to the north-west of the Ardennes. Its unofficial capital is Ciney. The region preserves the name of the Condrusi, a Germanic tribe which inhabited t ...

and

Ardennes The Ardennes (french: Ardenne ; nl, Ardennen ; german: Ardennen; wa, Årdene ; lb, Ardennen ), also known as the Ardennes Forest or Forest of Ardennes, is a region of extensive forests, rough terrain, rolling hills and ridges primarily in Be ...

regions of

Wallonia Wallonia (; french: Wallonie ), or ; nl, Wallonië ; wa, Waloneye or officially the Walloon Region (french: link=no, Région wallonne),; nl, link=no, Waals gewest; wa, link=no, Redjon walone is one of the three regions of Belgium—alo ...

are good examples of a succession of horst and graben. * The

Satpura Range The Satpura Range is a range of hills in central India. The range rises in eastern Gujarat running east through the border of Maharashtra and Madhya Pradesh and ends in Chhattisgarh. The range parallels the Vindhya Range to the north, and these ...

is a horst in India and is flanked by Narmada Graben in the north and much smaller but parallel Tapi Graben in the south.

References

{{Structural geology Structural geology

Features

Horst

Graben

Examples

See also

References