The UK and Swiss team found that, contrary to common scientific predictions, dense plates tend to be held in the upper mantle, while younger and lighter plates sink more readily into the lower mantle.
The mantle is a zone underneath the Earth's crust encompassing its super hot molten core. It is divided into an upper and lower area, and is made up of a 2,900 km circumference of churning, viscous rock. It is constantly fed with new material from parts of tectonic plates which slide down from the surface into it.
The researchers' numerical models show how old, dense and relatively stiff plates tend to flatten upon reaching the upper-lower mantle boundary, 'draping' on top of it. Their models are helping to explain plate movements and earthquakes in the Western Pacific, where old plates currently sink below Tonga, the Mariana Islands and Japan.
By contrast, younger more malleable plates tend to bend and fold above the boundary of the lower mantle for tens of millions of years until they form a critical mass that can sink rapidly into the lower mantle.
When this mass moves into the lower mantle, the part of the plate still at the surface is pulled along at high speed. This explains why plate movements below Central and northern South America are much higher than expected for such young plates.
The scientists came to these conclusions by using a numerical model, originally used to show how buildings buckle and fold, which calculates the brittleness, stiffness and elasticity of tectonic plates alongside how the pressures and stresses inside the mantle would affect the plate on its downward descent.
They then compared the modelling with plate movement data. By comparing the two models, the team was able to build up a clear picture of how plates should move when stalled in the upper mantle and also show, for the first time, how tectonic plate rock is mixing within the mantle.
Commenting about the study, lead researcher Dr Saskia Goes, from Imperial College London's Department of Earth Science and Engineering, said:
"It is exciting to see direct evidence of plates transiting from the upper and lower mantle. This process has been predicted by models before, but no one has been able to link these predictions with observations, as we now do for plate motions."
When two tectonic plates collide, with one sliding below the other and sinking into mantle, it can lead to the formation of mountain belts, like the Andes, and island arcs, like Japan and, in some places, cause explosive volcanism and earthquakes. Dr Goes say more research is needed, but believes this study could potentially help scientists determine earthquake risks in parts of these zones where none have ever been recorded before.
"The speed with which the two plates converge, and the force with which they are pushed together, determine the size of the largest earthquakes and time between large tremors. Understanding what forces control the plate motions will ultimately help us determine the chances for large earthquakes in areas where plates converge, in places like the northern U.S., Java and northern Peru, but where no large earthquakes have been recorded in historic times," she adds.
Colin Smith | EurekAlert!
UCI and NASA document accelerated glacier melting in West Antarctica
26.10.2016 | University of California - Irvine
Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
27.10.2016 | Life Sciences
27.10.2016 | Life Sciences
26.10.2016 | Power and Electrical Engineering