Search results
Results from the WOW.Com Content Network
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. [2] The plural of graben can be either graben or grabens. Graben form low-lying features such as basins and rift valleys. [1] [2] They can be very long relative to their width.
In physical geography and geology, a horst is a raised fault block bounded by normal faults. [1] Horsts are typically found together with grabens. While a horst is lifted or remains stationary, the grabens on either side subside. [2] This is often caused by extensional forces pulling apart the crust.
Graben often occur side by side with horsts. Horst and graben structures indicate tensional forces and crustal stretching. Graben are produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides.
Lake-filled half-graben showing sedimentation dominantly from the 'hinge' margin. Four zones of sedimentation can be defined in a half-graben. The first is "escarpment margin" sedimentation, found along the major border faults bounding the half graben, where the deepest part of the basin meets the highest rift-shoulder mountains. [6]
In the Canberra Graben and Cullarin Block, metamorphism mostly reached the upper greenschist stage, with shallow burial and temperature below 350 °C. This changed the volcanics and sediments with sericitisation , saussuritisation , conversion of plagioclase to albite , and conversion of biotite to chlorite , titanite , epidote and opaque minerals.
The Ottawa-Bonnechere Graben measures about 700 km (435 mi), running from the Montreal area on the east to near Sudbury and Lake Nipissing on the west. [2] On the east, it joins the Saint Lawrence rift system, a half-graben which extends more than 1000 km along the Saint Lawrence River valley and links the Ottawa and Saguenay Graben.
The Bresse Graben lies to the east of the Limagne Graben. Rifting started during the Eocene, pausing from the Late Oligocene to Middle Miocene before resuming in the Late Miocene. The eastern margin of the basin was overridden by thrust faults from the Jura Mountains , the leading edge of the Alpine thin-skinned deformation .
The Eger Graben is part of the European Cenozoic Rift System and was created geologically on the same principle as the Rhine Rift Valley. It was formed by the almost complete erosion of the Variscan Mountains and sits on a fault-block caused by the horizontal pressure of the African continental plate. This block dropped, however, in contrast to ...