from Wikipedia, the free encyclopedia
QA geosciences

This article was due to content flaws on the quality assurance side of Geosciences portal entered. This is done to increase the quality of the articles in the geosciences topic. Please help to correct the deficiencies or take part in the discussion .  ( + )
Reason: Article is unclear without sources, definition + demarcation to endogenous dynamics. - Jo 10:14, Dec. 8, 2008 (CET)

The Geodynamics is concerned with the natural movement processes in the Earth's interior or on the surface of the earth . At the same time, she researches the drive mechanisms and forces and force distributions with which the displacements are related .

Their findings are mainly obtained through methods of geophysics ; they also serve to interpret the mechanisms in the geological past. The term is often wrongly used for purely kinematic aspects of various deformations, i.e. without considering their dynamics and causes. This concerns u. a. the purely metrological recording of local crustal movements .

The term Geodynamics overlaps in some areas with the meaning of Erdspektroskopie , but not for phenomena used, the one the earthquake would assign.

Geodynamics as a scientific discipline, its object of investigation and its topics

The movements of the earth's body take place continuously and can occur within a radius of a few tens of meters, but also over thousands of kilometers. The investigation of large-scale processes naturally requires international cooperation. At the same time, the field of geodynamics represents an interdisciplinary bridge between several disciplines in the geosciences , in particular geophysics , geodesy and geology . But astronomy also plays its part, especially with phenomena of the earth's rotation and the definition of the reference system for the coordinates to be measured.

Geodynamic phenomena cover a wide range. Examples are:

Geodynamics is therefore not only a research topic for scientists , but also significant for society , for aid organizations and local to international politics .

Small-scale appearances

Large-scale appearances

Earth's interior and geodynamics

From the course of earthquake waves ( seismology ) and other data ( geology , tectonics , seismics, earth's gravitational field ), geophysics has been creating ever more accurate models of the earth's interior for about 100 years. Essentially, the earth has 4-5 shells : stony earth crust (10 to 80 km thick, 2-layered under continents ), viscous earth mantle (down to an average depth of 2898 km) and liquid earth core made of iron with a solid core in the center.

See in detail: Inner structure of the earth

Geodynamics researches the processes that take place in this system. The earth can be seen pictorially as a heat engine that converts the warmth of the earth's interior into motion. The resulting convection eddies ( comparable to the boiling of hot water or the uppermost layer of sun ) are the "engine" of the large-scale geodynamic phenomena . Its best-known is plate tectonics , which Alfred Wegener accepted in 1915 as a "continent shift", but was believed by almost no one at the time.

Movement of the plates and clods

As far as we know today, however, the continents are more passive. They are pushed apart by a few centimeters each year due to the formation of new seabed , because in the mid-ocean ridges new material constantly rises from the earth's mantle and cools laterally from the ridge. Since the earth does not expand, material has to get back into the earth's mantle elsewhere. This mainly happens in the subduction zones in the Pacific , which form the Pacific ring of fire with thousands of volcanoes and hundreds of earthquakes per year.

What was previously only suspected from coastal forms (Wegener: Africa / South America), geology and biology (related rocks and plants on the continental margins) has been able to be measured directly and to the centimeter since the 1980s : with laser and satellite geodesy, with refined global satellite navigation and with radio waves from the most distant quasars , whose differences in transit time are measured on large radio telescopes distributed around the world ( VLBI ).

In the meantime, the drift rates of every continental and sea plate (2–20 cm per year) can be specified with millimeter precision and geodynamically modeled. The correspondence between measurement and theory in the latest NIMA models is already in the cm range.

In-depth geophysical methods

In addition to the above-mentioned geometric measurements, z. B. Magnetotellurics contribute a lot to the understanding of the earth's body. The conductivity of the earth's crust and uppermost mantle - where the continents swim - can be examined magnetically . The subducted coconut plate under Mexico shows increased conductivity because mineral water is likely to collect from the submerged plate. It lowers the melting point of rocks and therefore allows magma to rise from the depths - which explains the well-known volcanic belts around the Pacific in particular .

It is still largely unclear why the earth “breathes” in such diverse ways, but not Mars or Venus (anymore). It is clear, however, that the earth has a large moon , and Venus and Mars do not.

About 90% of the earth's magnetic field is generated in the deep interior of the earth. Dynamo theory investigates whether the earth's rotation in the mantle and in the liquid core is slightly different . The models for generating the earth's magnetic field are summarized under the term geodynamo . One day it will be explained how mechanical energy is converted into magnetic energy and why the magnetic field has been weakening for thousands of years - or even reversing its polarity, as has been demonstrated on the ocean floor over the past millions of years. In this context, the repercussions on the earth and moon during the tide are increasingly taken into account in the models.

Near-surface geodynamics, geological faults

Geologists have long understood how to infer their movement since the Tertiary from the sequence of layers ( formations ) as well as their warping, dislocations or mineral content . The alpine and other mountain formations can now be easily explained and show e.g. B. that the sandstone- like flysch in the Alpine foothills of Austria, Bavaria and Switzerland comes from deep-sea areas of the former Mediterranean Sea . The African plate and its Adriatic spur have been pushing north for millions of years, which has arched up the Alps and continues to this day. The earthquakes in southern Europe, Turkey or on the edge of the Zagros Mountains can also be explained in this way.

But not only in high mountain rock layers are long-lasting pressure in folds down. With softer rock you can often see this in the low mountain range and even in the hill country .

When huge layers of rock are displaced many kilometers, it makes sense that the earth's crust develops various cracks. Such geological faults can be found everywhere in Central Europe. Some of them are no longer active, but others show recent crust movements of up to a few cm / year. Sinking movements in tectonic basins such as Pannonia , Vienna Basin , Upper Rhine Rift , etc. are often offset by uplifts in mountain ranges .

In sedimentary basins , it often happens that a leveling several such fault lines crossed. If this exact height measurement is repeated every 30–50 years (as is usually the case), the height differences between successive points show a time-dependent course. In this way, it is possible to determine without complicated models which of these fault lines, which are often tens of kilometers long, are still active.

Applied geophysics

Link between geophysics and geodesy

The large-scale effective geodynamic forces, on the other hand, come from the interior of the earth , which is why this part of geodynamics has so far been largely assigned to geophysics . The modern geodynamics today represents more of a link to geodesy , which in the last decades

builds numerous geophysically relevant surveying networks and global reference systems (especially ITRF ). More recent interdisciplinary activities are developing various projects in geotechnics and geodesy , particularly with regard to local crustal movements .

Astronomy also makes a decisive contribution to the latter aspects and to large-scale movement studies. Geodynamics has become a prime example of interdisciplinary and international cooperation in which geodetic and physical methods as well as small and large-scale working methods interact.

Monitoring of geohazards

Many of the earlier mass movements are only detected in the course of boreholes or soil surveys, when a large building is erected, a tunnel is built or an oil field is seismically or gravimetrically sounded out ( explored ). Today, such risks can be clarified in advance.

The environment of solifluction, possible landslides, unstable rock formations, in active magma areas and the large tunnels are continuously geodetically and electronically monitored ( monitoring ) in order to be able to trigger an alarm in the event of any acceleration of movement . They research the geophysical services under the heading of geohazards .

On damp slopes, the top layer of soil often crawls down into the valley, which can be seen in the saber growth of small trees: they strive to grow vertically - and therefore have to curve uphill for a number of years. On grassy slopes in the mountains you can sometimes see bare spots ( blaiken ), where the sod tears off and slides down like a corrugated carpet. Such movements often accelerate after heavy rains ; the moisture penetration or erosion can then even lead to the removal of mudslides . Therefore, cooperation with ecology , forestry and landscaping is important ( protected forest , afforestation , erosion control)

Tunnel construction, discordant layers and mountain damage

Miners and technicians in tunnel construction have long known that even massive rock can move . Many tunnels are continuously narrowed by the pressure of the mountains , and the walls of a tunnel usually have to be paved.

Thorough geodynamic research into these phenomena and forces has led to the development of the New Austrian Tunneling Method (NÖT), where the rock supports itself through a good choice of cross-section .

Another problem is the unexpected ingress of water in the tunnel. It often occurs with discordant stratification.

In the field of geodynamics, mining damage science also counts . However, she does not investigate natural effects, but rather soil movements caused by mining . First and foremost, there are subsidence that slowly continues from decaying tunnels to the surface of the earth , but also the mechanics of heaps and other phenomena are included.

Dynamic simulation

Another tool used by geodynamicists is called computational physics . There, the rock and layer parameters are changed in complex and therefore very computationally intensive computer simulations until the model shows realistic behavior. Because of the large amounts of data (the simulations cover large parts of the earth, which leads to many millions of grid points, and simulate processes over millions of years), sophisticated numerical methods , powerful algorithms and high-performance computers or computer clusters are required.

Geophysical services

Because of this interdependence and the public interest, authorities, research or testing institutes have been established in most countries that collect, interpret and, in some cases, make predictions about the most important geodynamic processes :

For earthquakes, but also for other geophysical topics, are important information points:

See also


  • Klaus Strobach: Our Planet Earth: Origin and Dynamics. Borntraeger, Berlin and Stuttgart 1991, ISBN 3-443-01028-8 .
  • Kurt Stüwe: Introduction to the geodynamics of the lithosphere: quantitative treatment of geoscientific problems. Springer, Berlin 2000, ISBN 3-540-67516-7 .

Web links

too large-scale geodynamics:

Individual evidence

  1. Volker Jacobshagen, Jörg Arndt, Hans-Jürgen Götze, Dorothee Mertmann, Carin M. Wallfass: Introduction to the geological sciences (=  university paperbacks . Volume 2106 ). Verlag Eugen Ulmer & Co., Stuttgart 2000, ISBN 3-8252-2106-7 , p. 69 .