New force driving Earth's tectonic plates discovered

July 6, 2011, University of California - San Diego
A view of the bends of the fracture zones on the Southwest Indian Ridge caused by the slowdown of Africa in response to the Reunion plume head. The image shows the gravity field. Credit: Scripps Institution of Oceanography,UC San Diego

Bringing fresh insight into long-standing debates about how powerful geological forces shape the planet, from earthquake ruptures to mountain formations, scientists at Scripps Institution of Oceanography at UC San Diego have identified a new mechanism driving Earth's massive tectonic plates.

Scientists who study tectonic motions have known for decades that the ongoing "pull" and "push" movements of the plates are responsible for sculpting continental features around the planet. Volcanoes, for example, are generally located at areas where plates are moving apart or coming together. Scripps scientists Steve Cande and Dave Stegman have now discovered a new force that drives plate tectonics: Plumes of hot magma pushing up from Earth's deep interior. Their research is published in the July 7 issue of the journal Nature.

Using analytical methods to track plate motions through Earth's history, Cande and Stegman's research provides evidence that such mantle plume "hot spots," which can last for tens of millions of years and are active today at locations such as Hawaii, Iceland and the Galapagos, may work as an additional tectonic driver, along with push-pull forces.

Reconstruction of the Indo-Atlantic Ocean at 63 million years, during the time of the superfast motion of India which Scripps scientists attribute to the force of the Reunion plume head. The arrows show the relative convergence rate of Africa (black arrows) and India (dark blue) relative to Eurasia before, during and after (from left to right) the period of maximum plume head force. The jagged red and brown lines northeast of India show two possible positions of the trench (the subduction zone) between India and Eurasia depending on whether the India-Eurasia collision occurred at 52 million years or 43 million years. Credit: Scripps Institution of Oceanography, UC San Diego

Their new results describe a clear connection between the arrival of a powerful head around 70 million years ago and the rapid motion of the Indian plate that was pushed as a consequence of overlying the plume's location. The arrival of the plume also created immense formations of now called the "Deccan flood basalts" in western India, which erupted just prior to the of dinosaurs. The Indian continent has since drifted north and collided with Asia, but the original location of the plume's arrival has remained volcanically active to this day, most recently having formed Réunion island near Madagascar.

The team also recognized that this "plume-push" force acted on other , and pushed on Africa as well but in the opposite direction.

"Prior to the plume's arrival, the African plate was slowly drifting but then stops altogether, at the same time the Indian speeds up," explains Stegman, an assistant professor of geophysics in Scripps' Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics. "It became clear the motion of the Indian and African plates were synchronized and the Réunion hotspot was the common link."

Images of the satellite derived gravity field over the Central Atlantic (top) and Southwest Indian Ridge (right) showing the zones of rough topography and sharp bends in the fracture zones that were caused by the slowing of Africa's motion as the Reunion plume head reached its maximum force. The inset globe shows the location of the gravity maps as well as the extent of the parallel zones of rough topography (outlined in red) on the flanks of the Mid-Atlantic and Southwest Indian ridges caused by the change in Africa's motion. Credit: Scripps Institution of Oceanography, UC San Diego

After the force of the plume had waned, the African plate's motion gradually returned to its previous speed while India slowed down.

"There is a dramatic slow down in the northwards motion of the Indian plate around 50 million years ago that has long been attributed to the initial collision of India with the Eurasian plate," said Cande, a professor of marine geophysics in the Geosciences Research Division at Scripps. "An implication of our study is that the slow down might just reflect the waning of the mantle plume-the actual collision might have occurred a little later."

Explore further: Breakthrough achieved in explaining why tectonic plates move the way they do

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Display comments: newest first

1.7 / 5 (11) Jul 06, 2011
Is there any info on the time machine they used to determine this?
3.9 / 5 (19) Jul 06, 2011
Is there any info on the time machine they used to determine this?
Whats your point exactly?
3.4 / 5 (5) Jul 06, 2011

The force may not actually be new. It would be better to say that "the forces acting on the earths crust have changed recently" or something along those lines. Using the word 'new' to describe previously unrecognized dynamics doesn't really do well. :)
4.5 / 5 (8) Jul 06, 2011
Is there any info on the time machine they used to determine this?

Yes: Rocks -- they collect, layer and finally tell tales.
3.8 / 5 (13) Jul 06, 2011

The force may not actually be new. It would be better to say that "the forces acting on the earths crust have changed recently" or something along those lines. Using the word 'new' to describe previously unrecognized dynamics doesn't really do well. :)
Plausable answer but I did not understand poofs comment on 'time machine' which is what I was responding to.
4 / 5 (4) Jul 06, 2011
Poof incorrectly thought that by "new," they meant that it's a recent phenomena, rather than a recent DISCOVERY.
5 / 5 (5) Jul 06, 2011
They might be overstating their case a bit. Mantle convection cells have long been the suspected motive force driving plate tectonics, but there are obviously other contributing phenomena: the worldocean- and ice- overburdens and planetary rotation are sure to have an effect, and I've heard speculation regarding the contribution of these so-called hot spots before, too- and their effect is probably due to a certain degree of "flooding", or lubrication, of the underside of the plates by high-temperature, low-viscosity basaltic magmas, which also -incidentally- rather easily incorporate H20- thereby becoming even more fluid. This would probably go a long way toward explaining the abrupt slow down of the Indian plate after it had ridden past the head end of the plume.

So, it would seem that this doesn't exactly qualify as a "Discovery", but rather as the first formal claim or assertion that it is a bona fide geophysical process of Plate Tectonics.

1 / 5 (1) Jul 07, 2011
Caliban, your inclusion of "flooding" and "H2O" as contributing factors sounds like a creationist geology. Is this your intent?
5 / 5 (1) Jul 07, 2011
I'm not sure how you derived that, Cin5456. The answer is NO. Maybe a closer reading will clear it up for you.
5 / 5 (1) Jul 07, 2011
Sorry, I ran into someone recently who justified the big flood with those terms and almost your exact words. I had to ask. I appolize for mistaking your intent.
Jul 11, 2011
This comment has been removed by a moderator.
1.7 / 5 (3) Jul 11, 2011
I presume, the Earth is surrounded with dense cloud of antineutrinos, which are forming the sparse density fluctuations around Earth of approximately dodecahedron geometry too. At the places where the concentration of antineutrinos is highests, the speed of Earth mantle heating is highest, because the earth is heated with decay of radioactive elements inside of Earth mantle and these antineutrinos are accelerating it. Therefore we can expect twenty hotspots regularly distributed along the Earth mantle. Note that increased density of antineutrinos around Earth should explain the reversal of magnetic poles, increased geovolcanic activity and the global warming at the recent time.

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