Why tectonic plates move the way they doJuly 17th, 2010 - 5:52 pm ICT by ANI
Washington, July 17 (ANI): Researchers at Monash University and Scripps Institution of Oceanography have developed a new theory to explain the global motions of tectonic plates on the earth’s surface.
The new theory extends the theory of plate tectonics - a kinematic description of plate motion without reference to the forces behind it - with a dynamical theory that provides a physical explanation for both the motions of tectonic plates as well as motion of plate boundaries. The new findings have implications for how scientists understand the geological evolution of Earth, and in particular, the tectonic evolution of western North America, in the past 50 million years.
The research, led by Monash University’s Wouter Schellart, appears in the journal Science.
These findings provide a new explanation as to why tectonic plates move along the Earth’s surface at the speeds that are observed, the details of which were previously not well-understood.
Schellart said: “The earth’s surface is covered with tectonic plates that move with respect to one another at centimetres per year. These plates converge at deep-sea trenches, plate boundaries where one plate sinks (subducts) below the other at so-called subduction zones. The velocities of these plates and the velocities of the boundaries between these plates vary significantly on Earth.”
Schellart and his team, including UC San Diego geophysicist Dave Stegman and Rebecca Farrington, Justin Freeman and Louis Moresi from Monash University, used observational data and advanced computer models to develop a new mathematical scaling theory, which demonstrates that the velocities of the plates and the plate boundaries depend on the size of subduction zones and the presence of subduction zone edges.
Stegman, who developed the computer models that helped the team reenact tens of millions of years of tectonic movement, said: “The scalings for how subducted plates sink in the earth’s mantle are based on essentially the same fluid dynamics that describe how a penny sinks through a jar of honey. The computer models demonstrate that the subducted portion of a tectonic plate pulls on the portion of the plate that remains on the earth’s surface. This pull results in either the motion of the plate, or the motion of the plate boundary, with the size of the subduction zone determining how much of each.
“In some ways, plate tectonics is the surface expression of dynamics in the earth’s interior but now we understand the plates themselves are controlling the process more than the mantle underneath. It means Earth is really more of a top-down system than the predominantly held view that plate motion is being driven from the bottom-up.”
This discovery explains why the Australian, Nazca and Pacific plates move up to four times faster than the smaller African, Eurasian and Juan de Fuca plates.”It also provides explanations for the motions of the ancient Farallon plate that sank into the mantle below North and South America. This plate slowed down during eastward motion from about 10 centimetres (four inches) per year some 50 million years ago to only 2 centimetres (0.8 inches) per year at present,” Schellart said.
The decrease in plate velocity resulted from the decrease in subduction zone size, which decreased from 14,000 kilometres (8,700 miles) to only 1,400 kilometres (870 miles).
“This had a dramatic effect on the topography and the structure of the North American continent. Until 50 million years ago, the west coast of North America was characterized by a massive mountain chain similar to the present day Andes in South America, and ran from Canada in the north to southern Mexico in the south,” said Schellart. (ANI)
- First dynamic model 'to explain' mystery of Mount Etna - Oct 08, 2010
- New theory on why some mountains form, crumble - Jul 16, 2010
- New study links mantle flow to 'uplift and volcanism in mobile belts' - Jun 03, 2010
- New discoveries resolve debate over oxygen in Earth's mantle - Dec 15, 2010
- Ocean sank 1,100 km into earth, raising chain of volcanic islands - Mar 06, 2009
- India might be sinking into Earth's mantle - Feb 01, 2010
- Earth's birth: Inert gases provide clues - Sep 27, 2011
- Rock defects below earth surface impact quakes - Apr 24, 2012
- Global 3D map indicates presence of water in certain areas of Earth's mantle - Aug 20, 2009
- Software shows how Earth evolved millions of years ago - Mar 17, 2011
- Indian crust sank 200 km after hitting Asian landmass - May 29, 2010
- New research improves odds of finding diamonds - Jul 15, 2010
- 200km deep subduction of Indian continent under Asia - May 29, 2010
- New theory to reveal why midcontinent faults generate earthquakes? - Jul 31, 2010
- Scientists report lower rate of quakes along some subduction zones - Dec 05, 2009
Tags: computer models, deep sea trenches, dynamical theory, farrington, geological evolution, geophysicist, institution of oceanography, journal science, monash university, new explanation, observational data, physical explanation, plate boundaries, plate motion, scripps institution of oceanography, stegman, tectonic evolution, tectonic plates, theory of plate tectonics, uc san diego