Geodynamics

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Geodynamics is concerned with the natural movement processes within the earth or on the earth's surface. At the same time, she explores the driving mechanisms and forces with which the shifts are related.

Their findings are primarily obtained by methods of geophysics; they also serve to interpret the mechanisms in the geological past. The term is often used erroneously for purely kinematic aspects of various deformations, ie without taking into account its dynamics and causes. This concerns, inter alia, the purely metrological determination of local crustal movements.

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

• 4.1 link Geophysics Geodesy
• 4.2 Monitoring of geohazards
• 4.3 Tunneling, discordant layers and mining
• 4.4 Dynamic Simulation

Area of ​​Interest

The movements of the earth take place continually and may occur within a few tens of meters, but also over thousands of kilometers. The study of large-scale processes requires by nature, international cooperation. Same time, the field of geodynamics an interdisciplinary bridge between several disciplines of geosciences is, especially in geophysics, geodesy and geology. But astronomy is doing its part, especially in the phenomena of the earth's rotation and the definition of the reference system for the coordinates to be measured.

Geodynamic phenomena range over a wide scale. Examples are:

• Small-scale movements: local subsidence to buildings and sediment layers
• Slow soil flow ( solifluction ) on a mountain slope, or a sudden landslide after heavy rainfall
• Landslides triggered by regional earthquakes, erosion, or defrosting permafrost
• In collaboration with the glaciology in the investigation of the rock movement in the glacier and permafrost areas
• In collaboration with the hydrology of the movements removal and installation of attachments
• Effects of volcanism in the Earth masses, such as italics, pyroclastic flows

• Horizontal and vertical crustal movements of entire regions
• Movements of active geological faults at the edges of sedimentary basins up to elongated fault lines along rivers or mountain areas
• Scholl movement and uplift of mountain ranges (eg the Alps (currently 1-3 mm / year) )

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

Small-scale phenomena

Large-scale phenomena

Erdinneres and Geodynamics

From the course of quake waves ( seismology ) and other data (geology, tectonics, seismology, earth gravity ) has created geophysics for about 100 years and more accurate models of the Earth's interior. In essence, the Earth has 4-5 cups: stony crust ( 10-80 km thick under continents in 2 shifts ), viscous mantle (up to the average depth of 2898 km ) and liquid Earth's core made ​​of iron with a solid core at the center.

Geodynamics explores the processes that take place in this system. Pictorial you can see the earth as a heat engine which converts the heat of the earth's crust movement. The convection occurring ( the bubbling hot water or the top layer of sun equivalent) are the " engine" of the large-scale geodynamic phenomena. Its most famous is plate tectonics, which was exactly 80 years ago Alfred Wegener accepted as " continental drift ", but back then believed by almost anyone.

Movement of the plates and plaice

According to current knowledge, however, the continents are rather passive. They are forced apart by the formation of new ocean floor a few centimeters per year, because in the mid-ocean ridges constantly rising new material from the mantle and cools from the back side. Since the earth does not expand material need to get back into the mantle elsewhere. This is mainly due to the subduction zones in the Pacific that make up the Pacific Ring of Fire with thousands of volcanoes and hundreds of earthquakes per year.

What was formerly only from coastal features (Wegener: Africa / South America ), geology and biology suspected ( related rocks and plants in the continental margins ), you can since the 1980s to measure directly and centimeter accuracy: with laser and satellite geodesy, with sophisticated global satellite navigation and with radio waves the most distant quasars, whose run-time differences are measured on globally distributed large radio telescopes ( VLBI ).

Meanwhile, you can specify the drift rates of each continental and seafood platter (2-20 cm per year) to the nearest millimeter and geodynamic modeling. The agreement between measurement and theory is the latest NIMA models already in the cm range.

Deep-seated geophysical methods

In addition to the above-mentioned geometric measurements such as the magnetotelluric also contributes much to the understanding of the earth's body. The conductivity of the Earth's crust and uppermost mantle - where the continents float - can be investigated magnetically. So shows the subducted beneath Mexico Cocos increased conductivity because mineral water of the subducting plate is likely to collect. It lowers the melting point of rocks and can therefore rising magma from the depths - which explains the known volcanic belt in particular to the Pacific.

Why is the earth so diverse "breathes", but Mars or Venus (no longer), it is still largely unclear. But it is clear that the Earth has one large moon, and Venus and Mars do not.

Approximately 90 % of the earth's magnetic field is generated in the deep interior of the earth. Whether the earth's rotation is slightly different in coat and liquid core, is explored in the form of a " dynamo process." These models are summarized under the term geodynamo. It should be one day explain how mechanical energy is converted into magnetic and why the magnetic field weakens for millennia - or even reverses the polarity, as it was demonstrated on the ocean floor over the past millions of years. In this context, the effects on the Earth and the Moon in the tide are increasingly included in the models.

Near-surface geodynamics, geological faults

It has long been understood by geologists to conclude from the sequence of layers ( formations ) and their deformations, dislocations or mineral contents, on their movement since the Tertiary. Thus, the alpine and other mountain formations are now well explained and shown, for instance, that the sandstone -like flysch in the foothills of Austria, Bavaria and Switzerland comes from deep waters of the former Mediterranean. The African plate and its Adriatic spur pushes for millions of years to the north, which has bulged the Alps and to this day still continues. The earthquake in southern Europe, Turkey or on the edge of the Zagros Mountains are explainable.

But not only in high mountain rock layers laid by prolonged pressure in wrinkles. In softer rock of the kind one sees often in low mountains and even in the hills.

When huge rock layers are shifted for many miles, is clear that the crust gets several cracks. Such geological faults can be found everywhere in Central Europe. Some of them are no longer active, at others, however, recent crustal movements show up to a few cm / year. Descending movements in tectonic basins as Pannonia, Vienna Basin, Upper Rhine Graben, etc. are often heave against in mountain ranges.

In sedimentary basins, it often happens that a leveling traverses several such fault lines. If this exact height measurement is repeated ( as is common ) every 30-50 years, show the height differences of consecutive points a time-dependent course. So it can be established without complicated models, which are often dozens of km long fault lines still active.

Applied Geophysics

Link Geophysics Geodesy

The large-scale active geodynamic forces stir, however, from the Earth's interior ago, which is why so far largely then assigned this part of Geodynamics Geophysics. The modern geodynamics is today more of a link to geodesy is that in recent decades

• New measurement methods - eg laser distance measurement and GPS, satellite gravimetry and remote sensing
• Or new ways of modeling - such as GIS and compensation calculation, monitoring the Earth's rotation ( IERS ) and global processes ( VLBI )

Numerous geophysical surveying relevant networks and global reference systems builds (especially ITRF ). Recent interdisciplinary activities develop different projects in Geotechnical Engineering and Geodesy, particularly with regard to local crustal movements.

Also astronomy contributes to the latter aspects and to large-scale movement studies in critical. Thus, the Geodynamics has become a prime example of interdisciplinary and international cooperation, cooperate in the geodetic and physical methods as well as small and Large scale ways of working.

Monitoring of geohazards

Many of the earlier mass movements are detected only in the course of drilling or soil testing, if a large building erected, constructed a tunnel or an oil field seismic or plumbed gravimetrically ( explored ) is. Today, such risks can explain in advance.

The area of solifluction, possible landslides, unstable rock formations in active magma areas and the large tunnels are constantly geodetic- monitored electronically (monitoring) in order to trigger an alarm when any possible acceleration of the movement can. The geophysical services they explore under the heading of geohazards.

On moist slopes often crawls the top layer of soil downhill, which can be seen on the saber growth of small trees: they seek to grow vertically - and must therefore several years continuously curving uphill. On grassy slopes in the mountains sometimes you see bald spots ( Blaiken ) where therefore tear off the turf and slips like a corrugated carpet down. Such movements accelerate often after heavy rains; the penetration or erosion can then even lead to disposal of debris flows. Therefore, it is also working with ecology, forestry and landscaping of importance ( protected forest, reforestation, erosion limit)

Tunneling, discordant layers and mining

That also solid rock can move, is the mountain man and the technician in tunneling has long been familiar. Many tunnels are narrowed continuously through the rock pressure, and the walls of a tunnel must be attached as a rule.

Thorough investigation of these geodynamic phenomena and forces have led to the development of the New Austrian Tunnelling Method (NATM ), where the rock is supported by good choice of the cross section itself.

Another problem is the unexpected flooding in the tunnel. It often occurs in discordant stratification.

In the area of ​​geodynamics include the Mining Subsidence Engineering. However, it is not looking natural effects, but caused by mining ground movements. First and foremost, there are cuts that slowly continued from decaying tunnels to the surface, but also the mechanics of heaps and other symptoms, these include.

Dynamic Simulation

Another tool is called the Geodynamiker Computational Physics. There, in complex and therefore very compute-intensive computer simulations, the rock and layer parameters are varied until the model has a realistic behavior. Because of the large amounts of data ( the simulations include large parts of the earth, resulting in many millions of grid points, and simulate processes over millions of years ) are sophisticated numerical methods, efficient algorithms and high-performance computers or computer clusters needed.

Geophysical services

Because of this interdependence and the public interest were in most States authorities, established research and experimental institutions that collect data on the major geodynamic processes, interpret and sometimes even predictions:

• Engineering geology and slip areas,
• Earthquake and vulnerable zones
• Active volcanoes (outside Central Europe ), tsunamis, etc.

For earthquakes, but other issues are important geophysical information points:

• Earthquake services in Germany: BGR Hannover, GFZ Potsdam, Bavaria, Hesse, North Rhine-Westphalia and other
• Austria: Central Institute for Meteorology and Geodynamics, earthquake prediction / protection
• Switzerland: Swiss Seismological Service and Quaking Switzerland
• Links to the Czech Republic, Hungary, Italy and worldwide