Fracture tectonics

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With faulting or Bruchschollentektonik be geodynamic processes refer to operations where crustal areas, so-called broken floes , along more or less vertical fault planes moving. Larger raised clods or clod complexes that rise well above their surrounding area on the surface of the earth are referred to as clod mountains . Fold and ceiling tectonics are to be distinguished from fracture tectonics , which are characterized by fracture-free deformation or movement along more or less horizontal fault surfaces.

Bruchschollengebirge and rift valleys

The cause of the formation of rocky clods are tectonic tensions, which are often related to plate tectonic processes . In contrast to fold mountains (collision orogens), which arise in the collision zone at the plate edges, fracture clod mountains form at a certain distance from the edges of the colliding crustal blocks. This is also called intraplate deformation .

Schematic representation of an eyrie and trench structure with shear zones in between
Schematic representation of a lectern

The tectonic tensions either create new faults in the crust of the plate interior or reactivate old, already existing faults. In the case of broken clods, a block of crust limited by faults is lifted out of the subsoil. Such a prominent clod is also known as an eyrie . A mountain range only forms, however, if the uplift occurs faster than the erosion that attacks the uplifting clod on the surface of the earth. The Harz Mountains offer a classic example of a rocky clod mountain range . If the uplift occurs more strongly on one side of the clod than on the other sides, it is also referred to as a shed clod . The Ore Mountains are a typical Pultschollen Mountains . Both in the case of the Harz Mountains and the Ore Mountains, the uplifting of the clod and the action of erosion exposed the old Variscan basement . In these cases, one therefore speaks of basement eruptions .

While the resin was pushed out of the subsurface by compressive stresses (crust compression), fracture tectonics can also be extensive, i.e. due to crust expansion. It is assumed that the Upper Rhine Graben and the eyries flanking it with the Vosges and the Palatinate Forest in the west and the Black Forest and Odenwald in the east are due to tensile stresses that acted across the compressive stresses emanating from the Alps. The Basin and Range Province in North America is also the result of extensive crustal expansion, probably caused by a relaxation of the compressive stresses on the interior of the continent associated with the subduction of the Farallon Plate on the western edge of North America.

See also

literature

  • Frank Ahnert: Introduction to Geomorphology. 4th edition. Verlag Eugen Ulmer, Stuttgart 2009, ISBN 978-3-8252-8103-8 , p. 37
  • Lukas Plan: fractional tectonic structures. Speleo Leaflets, C24a. Association of Austrian Speleologists (VÖH), 2005 ( PDF )

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