Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Continental tug-of-war - until the rope snaps

19.07.2016

Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases

Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana and Laurasia, the current continents move at speeds of 20 to 80 millimeters per year characterizing today’s plate tectonics.


The extension velocity of tectonic plates increases rapidly during continental separation. The reason is that plate speed is dependent on the strength of the rift zone, which decreases abruptly during continental stretching – similar to a rupturing rope. (Fig: GFZ, S.Brune , G. Schwalbe , S. Riedl)


Acceleration of South America during the separation from Africa. Within a few million years the speed of the continent increases from 7 to 40 millimeters per year. (Fig.: S. Brune, GFZ)

Continental breakup is still not completely scientifically understood. New research, published in the scientific journal "Nature" shows that the continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.

Of course these processes have to be seen from the geological perspective: we are talking about plates moving slowly over long time periods, centimeters per year and millions of years, respectively. South America for instance separated from Africa over a period of approximately 40 million years.

The separation process, called 'rifting' by geoscientists, began about 150 million years ago, while the two tectonic plates diverged only with 5 to 7 millimeters per year. This slowly thinned the earth's crust and led to the formation of a basin. Before the two continents separated, however, the rift velocity increased six-fold to around 40 millimeters per year. Today Africa and South America drift apart annually with about 35 millimeters per year.

"Imagine the rope snapping during a tug-of-war" describes Sascha Brune from the GFZ German Research Centre for Geosciences, lead author of the study. "At first the rope strains slowly and imperceptibly, when one fiber breaks the overall strength of the rope doesn’t change much; but rupture of the last few rope fibers occurs very abruptly."

Together with colleagues from the University of Sydney the scientist has investigated numerous different rift zones worldwide and found that many continental breakups proceeded according to this two-phase speed evolution: "Most dramatic was the case of the separation of North America and Africa," says Brune. "Roughly 240 million years ago, divergence began very slowly with only one millimeter per year." 200 million years ago, however rifting accelerated by 20 times.

Intriguingly, rift acceleration typically began about ten million years before the actual rupture of the continent, as seen during the separation of Australia and Antarctica, North America and Greenland, Africa and South America, in the North Atlantic or the South China Sea.

Therefore, the newly formed continental margins are significantly shaped by both speed stages: first, slow rifting formed the shelf regions that today are located not far below sea level and near to the coast. In the second phase the distal, deep-water domains of the continental margin were formed at higher rift velocity inducing enhanced faulting and greater volcanic activity.

The new geoscientific results have important implications for the theory of plate tectonics: today's movements of the tectonic plates are known to be governed by the descent and collision of plates and by the currents of Earth’s deep mantle. During the breakup of continents, however, rapid plate accelerations are controlled by the weakening of the continent itself and not primarily by processes in the deep interior of the Earth.

Sascha Brune, Simon E. Williams, Nathaniel P. Butterworth, and R. Dietmar Müller: ”Abrupt plate accelerations shape rifted continental margins”, Nature AOP, 18.07.2016, DOI 10.1038/nature18319

Dipl.Met. Franz Ossing | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Further information:
http://www.gfz-potsdam.de/

More articles from Earth Sciences:

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

nachricht Modeling magma to find copper
13.01.2017 | 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: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

17.01.2017 | Materials Sciences

Smart homes will “LISTEN” to your voice

17.01.2017 | Architecture and Construction

VideoLinks
B2B-VideoLinks
More VideoLinks >>>