Berechnete gegenwärtige Wärmestromverteilung an der Kern-Mantel-Grenze
Einfluss von Subduktionsvorgängen auf die Verteilung des Wärmestroms
It is known that the Earth's magnetic field is produced by convection currents of an electrically conducting iron-nickel alloyin the liquid core, about 3,000 kilometers below the earth's surface. The geomagnetic field is highly variable, there are changes in Earth's magnetic field on a multitude of spatial and temporal scales. Above the liquid outer core is the mantle, the rock in which behaves plastically deformable due to the intense heat and high pressure.
At the boundary between Earth's core and mantle at 2900 km depth there is an intense heat exchange, which is on the one hand directed from the Earth's core into the mantle. On the other hand, processes within Earth's mantle in turn also affect the heat flow. The interesting question is how the much slower flow in the solid mantle influences the heat flow and its spatial distribution at the core-mantle boundary, and how this will affect the Earth's magnetic field which is produced due to the much faster currents in the Earth's core.
/Key variable heat transfer/
"The key variable is the heat flow. A cooler mantle accelerates the flow of heat from the hot core of the Earth, and in this way alters the also heat-driven convection in the Earth's core", said Bernhard Steinberger of the GFZ German Research Centre for Geosciences. "Ocean floor sinking into the mantle due to tectonic processes can lead to cooling in the mantle. They cause at these sites an increased heat flow into the cooler parts, namely until they have been heated to the ambient temperature." That might take several hundred million years, however.
Conversely, the hot core of the Earth leads to the ascent of heated rocks in form of large bubbles, so-called mantle plumes that separate from the core-mantle boundary and make their way up to the surface of the earth. This is how Hawaii came into existence. This increases the local heat flux out of the earth's core and in turn modifies the generator of the geomagnetic field.
/Reversals of the magnetic field/
In the Earth's history, polarity reversals of the geomagnetic field are nothing extraordinary. The most recent took place only 780 000 years ago, geologically speaking a very short period of time. The research team was able to determine that in the period of 200 to 80 million years before present, reversals initially happened more often, namely up to ten times in hundred million years. "Surprisingly, these reversals stopped about 120 million years ago and were absent for nearly 40 million years," explains GFZ scientist Sachs. Scientists presume that the reason for this is a concurrent reorientation of the whole mantle and crust with a shift in the geographic and magnetic poles of about 30°. Known as "true polar wander", thisprocess is caused by a change in density distribution in the mantle. If it increases the heat flux in equatorial regions, it would presumably lead to more frequent field reversals, if it decreases it, the field reversal might not occur.
/Looking to the future/According to current knowledge, therefore, an influence of plate tectonics and mantle convection on the Earth's magnetic field seems quite possible. The article also shows, however, that further research is still needed for a better understanding of these relationships. In particular, more episodes of "true polar wander" should be derived from paleomagnetic data, and it should be determined whether these are usually associated with an altered behavior of the magnetic field (e.g. frequency of field reversal). Also, future models for the generation of the geomagnetic field should investigate the influence of the spatial and temporal variation of the heat flux at the core-mantle boundary in more detail.
Images in printable resolution and an animation can be found at: http://www.gfz-potsdam.de/portal/gfz/Public+Relations/M40-Bildarchiv/Magnetfeld_Waermefluss
contact : Dr. Bernhard Steinberger, +49-331-288 1881
F.Ossing | EurekAlert!
The struggle for life in the Dead Sea sediments: Necrophagy as a survival mechanism
26.03.2019 | Geological Society of America
Mangroves and their significance for climate protection
26.03.2019 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)
Cancers that display a specific combination of sugars, called T-antigen, are more likely to spread through the body and kill a patient. However, what regulates...
DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.
The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...
Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.
The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...
Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.
Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
26.03.2019 | Physics and Astronomy
26.03.2019 | Physics and Astronomy
26.03.2019 | Physics and Astronomy