Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Is old rock really as "solid as a rock"

08.09.2015

Deformed craton under North America

In the course of billions of years continents break up, drift apart, and are pushed back together again. The cores of continents are, however, geologically extremely stable and have survived up to 3.8 billions of years. These cores that are called cratons are the oldest known geological features of our planet.

It was assumed that the cratons are stable because of their especially solid structure due to relatively low temperatures compared to the surrounding mantle. A team of German-American scientists now discovered that these cratons that were assumed to be “as solid as a rock” are not that solid after all.

The team headed by Dr. Mikhail Kaban from the GFZ German Research Centre for Geosciences now discovered that the craton below the North American continent is extremely deformed: its root is shifted relative to the center of the craton by 850 kilometers towards the west-southwest.

This fact is in contrast to the prevailing assumptions that these continental roots did not undergo substantial changes after their formation 2.5 to 3.8 billion years ago. The study that appears in the latest online publication of "Nature Geoscience" contradicts this traditional view.

“We combined and analyzed several data sets from the Earth’s gravity field, topography, seismology, and crustal structure and constructed a three dimensional density model of the composition of the lithosphere below North America”, explains GFZ scientist Mikhail Kaban. “It became apparent that the lower part of the cratonic root was shifted by about 850 kilometers.”

What caused the deformation of the stable and solid craton? A model of the flows in the Earth’s mantle below North America, developed by the scientists, reveals that the mantle material below 200 kilometers flows westward at a velocity of about 4 millimeters per year.

This is in concordance with the movement of the tectonic plate. Due to the basal drag of this flow the lower part of the cratonic lithosphere is shifted.

“This indicates that the craton is not as solid and as insensitive to the mantle flow as was previously assumed”, Kaban completes. There is far more mechanical, chemical, and thermal interaction between the craton of billions of years in age and its surrounding in the upper mantle of the Earth than previously thought.

Mikhail K. Kaban,Walter D. Mooney and Alexey G. Petrunin, 2015: “Cratonic root beneath North America shifted by basal drag from the convecting mantle”, Nature Geoscience, Advance Online Publication, DOI: 10.1038/NGEO2525

Franz Ossing
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Deutsches GeoForschungsZentrum
- Head, Public Relations -
Telegrafenberg
14473 Potsdam / Germany
E-Mail: ossing@gfz-potsdam.de
Tel. +49 (0)331-288 1040
Fax +49 (0)331-288 1044
www.gfz-potsdam.de

Franz Ossing | Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences
Further information:
http://www.gfz-potsdam.de/en/media-communication/press-releases/details/article/sind-steinalte-gesteine-wirklich-steinhart/

More articles from Earth Sciences:

nachricht How is climate change affecting fauna in the Arctic?
22.05.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Sea level as a metronome of Earth's history
19.05.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

Im Focus: Hydrogen Bonds Directly Detected for the First Time

For the first time, scientists have succeeded in studying the strength of hydrogen bonds in a single molecule using an atomic force microscope. Researchers from the University of Basel’s Swiss Nanoscience Institute network have reported the results in the journal Science Advances.

Hydrogen is the most common element in the universe and is an integral part of almost all organic compounds. Molecules and sections of macromolecules are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

Media accreditation opens for historic year at European Health Forum Gastein

16.05.2017 | Event News

 
Latest News

New approach to revolutionize the production of molecular hydrogen

22.05.2017 | Materials Sciences

Scientists enlist engineered protein to battle the MERS virus

22.05.2017 | Life Sciences

Experts explain origins of topographic relief on Earth, Mars and Titan

22.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>