Earth and Moon

Earth's crust faults

Earth's crust faults

Failures are a type of deformation of the earth's crust that ends in rupture, resulting in a wide variety of geological structures.

One of the accidents of the terrain that can be observed more easily are these failures or ruptures of a folding, especially if the terrain is of sedimentary type.

When this break occurs abruptly, an earthquake occurs. Sometimes, the fault line allows, at certain points, the magma of the lower layers to emerge and form a volcano.

Parts of a fault

He fault plane it is the surface on which the movement, horizontal, vertical or oblique, has occurred. If the fractures are fragile, they have smooth and polished surfaces due to abrasion. Fragments of different sizes can be released during the displacement of fractured rocks.

The failure lips They are the two edges or blocks that have moved. When vertical displacement occurs, the edges are called sunken (or inner) and raised (or superior) lip, depending on the location of each of them relative to the relative horizontal. When inclined, one of the blocks slides over the other. The block that is above the fault plane is called the "roof" and the one below the "wall".

He fault jump it is the vertical distance between two strata that originally formed a unit, measured between the edges of the raised block and the sunken one. This distance can be only a few millimeters (when the break occurs), up to several kilometers. The latter case is usually the result of a long geological process over time.

Types of failures

In a normal failure, produced by tensions, the inclination of the fault plane coincides with the direction of the sunken lip. The result is a stretch or elongation of the materials, when the sunken lip moves due to the force of gravity.

In the tear faultsIn addition to the upward movement, the blocks also move horizontally. If sufficient time passes, erosion can flatten the walls destroying any trace of rupture, but if the movement is recent or very large, it can leave a visible scar or a cliff-shaped scarp of failure. A special example of these types of failures are those transformers that move the ocean ridges.

In a reverse fault, produced by the forces that compress the earth's crust, the lip sunk in the normal fault, ascends on the fault plane and, in this way, the rocks of the oldest strata appear placed on the most modern strata, thus giving rise to the riding

The rotation failures or scissors are formed by the effect of the swinging of the blocks on the fault plane, that is, one block has rotational movement with respect to the other. While one part of the fault plane appears to be a normal fault, in the other it seems an inverse fault.

A tectonic massif or tectonic pillar, also called "Horst", is an elevated region limited by two normal, parallel faults. It may happen that on the sides of the horst there are series of normal failures; in this case, the slopes of the mountains will be formed by a succession of tiered levels. In general, tectonic massifs are elongated mountain ranges, which do not appear isolated, but are associated with tectonic pits. For example, the center of the Iberian Peninsula is occupied by the tectonic massifs that form the Sierra de Gredos and Guadarrama.

Finally, a tectonic pit o Graben is a fault association that results in a depressed region between two raised blocks. Tectonic graves occur in areas where at least two normal faults are grouped. The graves form valleys that can measure tens of kilometers wide and several thousand kilometers long. The valleys are filled with sediments that can reach hundreds of meters thick. This is the case, for example, in the Tagus River valley, on the Iberian Peninsula.

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