A
graben is a
depressedDepression in geology is a landform sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms, and may be referred to by a variety of technical terms.*A basin may be any large sediment filled depression...
block of land bordered by parallel faults.
Graben is
GermanGerman is a West Germanic language, thus related to and classified alongside English and Dutch. It is one of the world's major languages and the most widely spoken first language in the European Union. Around the world, German is spoken by approximately 105 million native speakers and also by...
for
ditch.
A graben is the result of a block of land being downthrown producing a
valleyIn geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
with a distinct
scarpIn geomorphology, an escarpment is a transition zone between different physiogeographic provinces that involves a sharp, steep elevation differential, characterized by a cliff or steep slope. Usually escarpment is used interchangeably with scarp...
on each side. Grabens often occur side-by-side with
horstIn physical geography and geology, a horst is the raised fault block bounded by normal faults or graben. A horst is formed from extension of the Earth's crust...
s. Horst and graben structures are indicative of tensional forces and crustal stretching.
Graben are produced from parallel normal faults, where the hanging wall is downthrown and the footwall is upthrown. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between grabens, the bounding faults of a horst typically dip away from the center line of the horst.
A single graben or multiple grabens can produce a
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...
.
Half-grabens
In many rifts the grabens are asymmetric, with a major fault along only one of the boundaries, and these are known as half-grabens. The polarity (throw direction) of the main bounding faults typically alternate along the length of the rift. The asymmetry of a half-graben strongly affects syntectonic deposition. Comparatively little
sedimentSediment is any particulate matter that can be transported by fluid flow, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers...
enters the half-graben across the main bounding fault, due to the effects of footwall uplift on the drainage systems. The exception is at any major offset in the bounding fault, where a relay ramp may provide an important sediment input point. Most of the sediment will enter the half-graben down the unfaulted hanging wall side (e.g.
Lake BaikalLake Baikal is the world's second most voluminous lake, after the Caspian Sea. It is the most voluminous freshwater lake in the world with an average depth of 744.4 m and contains a total of roughly 20 percent of the world's surface fresh water...
).
Famous grabens
- The Basin and Range Province of southwestern North America
North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
is an example of multiple horst/graben structures, including Death ValleyDeath Valley is a desert located in the southwestern United States. It is the lowest, driest, and hottest location in North America. Badwater, a basin located within Death Valley, is the specific location of the lowest elevation in North America at 282 ft below sea level...
.
- The Rhine
The Rhine is one of the longest and most important rivers in Europe, at , with an average discharge of more than ....
valley to the northNorth is one of the four cardinal directions, specifically the direction that, in Western culture, is treated as the fundamental direction:* North is used to define all other directions....
of BaselBasel is Switzerland's third most populous city . With 830000 inhabitants in the tri-national metropolitan area , Basel is Switzerland's second-largest urban area....
, SwitzerlandSwitzerland , officially the Swiss Confederation , is a federal republic consisting of 26 states named cantons, with Bern as the seat of the federal authorities...
- The Oslo graben
The Oslo Graben or Oslo Rift is a graben formed during a geologic rifting event in Permian time, the last phase of the Variscan orogeny. The main graben forming period began in the late Carboniferous, which culminated with rift formation and volcanism, with associated rhomb porphyry lava flows...
around Oslois the capital and largest city in Norway. Founded around 1048 by King Harald III of Norway, the town was largely destroyed by a fire in 1624. The Danish–Norwegian king Christian IV rebuilt the city as Christiania . Oslo, then an alternative name, became official again in 1925...
, NorwayNorway , officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
- The East African Rift
The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. It is part of the larger Great Rift Valley. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates...
Valley
- The Saguenay River
The Saguenay River is a major river of Quebec, Canada.It drains Lac Saint-Jean in the Laurentian Highlands, leaving at Alma and running east, and passes at the city of Saguenay. It drains into the Saint Lawrence River at Tadoussac.The river has a very high flow rate and is bordered by steep cliffs...
Valley
- The Narmada River
The Narmada the Periplus Maris Erythraei calls it the Nammadus.. The British Raj called it the Nerbudda or Narbada[] is a river in central India and the fifth largest river in the Indian subcontinent. Narmada is a Sanskrit word meaning 'the Giver of Pleasure'...
valley in central India
- The lower Godavari River
The Godavari is a river that runs from western to southern India and is considered to be one of the big river basins in India...
valley in southern India
- The Ottawa-Bonnechere Graben
The Ottawa-Bonnechere Graben with its branch the Timiskaming Graben, is an ancient rift valley in the Canadian Shield of Northeastern Ontario and Quebec, Canada. This rift valley was formed when the Earth's crust moved downward about a kilometer between two major fault zones known as the Mattawa...
in OntarioOntario is a province located in east-central Canada, the largest by population and second largest, after Quebec, in total area. Ontario is bordered by the Canadian provinces of Manitoba to the west and Quebec to the east, and 5 U.S...
and QuebecQuebec is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking identity and the only one whose sole official language is French at the provincial level....
, CanadaCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
- The Lambert Grabens
Lambert Grabens is a graben in Antarctica and contains the largest glacier in the world, Lambert Glacier.-External links:*...
in Antarctica| style="border-top:solid 1px #ccd2d9; padding:0.4em 1em 0.4em 0; vertical-align:top;" | 14,000,000 km
2 280,000 km
2 13,720,000 km
2 |-! style="border-top: solid 1px #ccd2d9; padding: 0.4em 1em 0.4em 0; vertical-align: top;...
- Gulf of Saint Vincent in South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories....
, AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
- The Guanabara Bay
In Portuguese, Baía da Guanabara is an oceanic bay located in southeastern Brazil in the state of Rio de Janeiro. On its Western shore lies the city of Rio de Janeiro, and on its Eastern shore the cities of Niterói and São Gonçalo. Four other municipalities surround the bay's shores...
in Rio de JaneiroRio de Janeiro is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America. The city was the capital of Brazil for nearly two centuries, from 1763 to 1822 during the Portuguese colonial era, and...
, Brasil