In this article, we examine the issue of natural phenomena. What are grabens and how do they form? Also, looking ahead, we pay attention to the opposite of graben - this is a handful.
What is graben
Graben is the sagging part of the earth's crust, which was formed as a result of a tectonic fault and stands out among the elevated areas.
Grabens usually appear as a result of the emergence of tensile forces near elevated areas of land. Under the influence of this, subsidence of the soil occurs and a failure of the rock formations is formed.
On the edges of the graben appear towering parts that are formed as a result of the accumulation of new rocks, they are called "graben wings".
In length, they can reach several tens and hundreds of kilometers - in width. The most pronounced and widely known grabens are in East Africa. They are located along the lakes of Tanganyika, Victoria, Nyansa. In Russia, the largest graben is the Barguzinsky Depression, the basin of Lake Baikal.
In the solar system, the largest graben is the Mariner Valley, located on Mars. The reason for the formation is volcanic activity.
What is a horst
A horst is a block of the earth's crust raised along faults formed as a result of tectonic movements.
Regarding the surface, there are three types of horsts:
- Inclined - the surface over the entire area is inclined in one direction.
- Wedge-shaped - there is a stepwise narrowing down.
- One-sided - faults or faults occur on one side only.
Often, horsts create mountains with flat peaks. The length usually reaches hundreds, and the width is tens of kilometers, the height is several thousand meters. Bright examples of horsts are the mountain range in Spain, Sierra Nevada, a mountain range in the south-west of Germany, the Black Forest.
For the first time the term "horst" was introduced in the science of geology in 1873 by the Austrian Edward Suess. In their own words, graben is a hollow, a handful is a hill.
Rift zones
Rift - a linearly horizontal large depression in the earth's crust. Usually this is a collection of depressions, occupying a vast area.
There are two types of rift zones - oceanic and continental.
The former arise as a result of the effect of magmatic melt coming from the depths of the Earth to the ocean floor. Magma under pressure pushes hard lithospheric plates; as a result of this process, a young oceanic crust is formed.
Continental rift zones are formed as a result of the rise of plumes (hot mantle) to the surface, with active volcanism, the continental crust is thinning and stretching. Such rifts can lead to the formation of a new ocean. In the East African rift system, namely in the Afar region, oceanic young crust has formed in some places.
Rifts that stopped in development and did not turn into oceans are called aulacogens. Usually in such places deposits of natural resources are formed. For example, the Devonian Donetsk Trough is a large coal deposit.
Usually the combination of horst-graben is aulacogen.