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
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
- Head, Public Relations -
14473 Potsdam / Germany
Tel. +49 (0)331-288 1040
Fax +49 (0)331-288 1044
Franz Ossing | Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences
NASA sees the end of ex-Tropical Cyclone 02W
21.04.2017 | NASA/Goddard Space Flight Center
New research unlocks forests' potential in climate change mitigation
21.04.2017 | Clemson University
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy