Long valley

from Wikipedia, the free encyclopedia

A longitudinal valley is an elongated indentation , mostly occupied and shaped by a river , between two approximately parallel mountain ranges , as is often found in geologically young fold mountains such as the Alps , Carpathians , Andes or the high mountains of Central Asia.

The term is mainly used when a mountain range also has distinctive transverse valleys , where rivers cut through mountain ranges in so-called breakthrough valleys .

Many longitudinal valleys follow the course of significant geological faults . These are related to the tectonic movements during the mountain formation, which in turn go back to plate tectonic processes. The faults can be structures that reach deep into the lower crust of the earth , which were already created before the actual mountain formation and were later reactivated, e.g. B. the Periadriatic Line in the Alps. For the formation of long valleys, however, cover thrusts also play an important, if not the most important, role. The ceiling structure, which many young fold mountains have, is to a large extent responsible for the morphological division of a mountain belt into more or less parallel mountain ranges. Longitudinal valleys preferably run along the so-called nappe foreheads (“thrust fronts”), which are oriented roughly across the movement path of the tectonic nappes, which in turn corresponds to the movement path of the collided continental blocks. This configuration results in a course with the deletion of the geological units, which is an important definition criterion for a longitudinal valley. Accordingly, a transverse valley runs across the strike .

In the case of particularly long valley systems that are occupied by several rivers, possibly with opposite flow directions, one speaks of longitudinal valley furrows . The Eastern Alps and other Alpine mountains have many such furrows, which stretch almost in a straight line over many hundreds of kilometers and may have been accentuated by glaciers during the Pleistocene . Some examples are:

The line Oberes Rhonetal - Vorderrhein can also be considered a longitudinal valley furrow , although it is separated by the Furka and Oberalp passes.

Notes and individual references

  1. ↑ Christiane Martin, Manfred Eiblmaier (ed.): Dictionary of earth sciences. 6 volumes. Spektrum, Akademischer Verlag, Heidelberg et al. 2000–2002, ISBN 3-8274-1655-8
  2. ↑ In the section of the valleys of Salzach and Enns, this longitudinal valley furrow goes back to the SEMP line , which continues to the east, morphologically far less noticeable, in the valley of the Salza , whereas the morphologically dominant longitudinal valley already merges before the confluence of the Salza with the Enns the valleys of Palten and Liesing continue in the Mur-Mürz furrow.