A diagram of a subduction zone, where one plate is pushed under the other, dragging the rest of the plate behind it.
Credit: NASA
SYDNEY: A new theory explains why tectonic plates move at different rates and solves other long-standing problems in Earth sciences, Australian scientists said.
The rate at which tectonic plates move depends on the width of its associated subduction zone - a place where two tectonic plates meet, and the thicker plate is pushed under the other.
The theory explains why the Australian Plate moves much faster than other plates, and explains the disintegration of a mountain range in North America, among other puzzles.
Subduction zones affect plate velocity
Previous theories and hypothesises, such as the idea that plate velocity depended on the age of the plate, have been unable to explain simultaneously the velocity of the different plates and the velocity of subduction zones.
But when geoscientist Wouter Schellart from Monash University in Melbourne, Australia, and his team compiled measurements of all the tectonic plates - 15 large tectonic plates and 30 smaller ones - and all the subduction zones on Earth, they noticed a clear pattern:
"The width of the subducted plate that has gone down into the mantle at the subduction zone determines the velocity of both the plate and the subduction zone plate boundary," said Shellart, whose finding were reported in the journal Science.
Ancient mysteries of tectonic plates
The researchers also ran an advanced four-dimensional computer simulation of the Earth's plates and their subduction zone boundaries. "We found the same velocities and patterns as observed in the data, thereby confirming our hypothesis."
This research helps solve some ancient mysteries involving plate tectonics. The ancient Farallon Plate, once called the Juan de Fuca Plate and located where Utah in the U.S. sits today, slowed down from 10 cm per year 50 million years ago to just two centimetres per year today.
Schellart and his team showed that during this period the subduction zone reduced in size from 14,000km to only 1,400km, which was the cause for the slowing of the plate, and the crumbling of an associated mountain range.
Subduction Zone
The "thicker plate" does not go under the thinner one. Oceanic crust subducts because it is more dense than continental crust. Continental crust is actually much thicker than oceanic.
plate tectonic proved to be wrong. scientist.g..ponmudi.
South America Africa India and Australian continents are believed to be moving away from the central Antarctica continents by sea floor spreading process is proved to be wrong.
researchers who believe that all the continents are moving also believe that new sea floor is being formed at the Central region of the Atlantic ocean.a process which the called sea floor spreading .
according to them new sea floor is formed in that region by upwelling magma which surfaced and cooled and solidified and finally formed new sea floor rock.as the process continue new sea floor rocks are formed in the central region which pushing the old sea floor rock to the side.
therefore the sea floor is moving in opposite direction therefore the continents of south America and Africa which is said to be on the moving plate also moving in opposite direction(east-west).
this kind of sea floor spreading can be called as longitude spreading since all the longitude have same length.so there is no problem in this kind of explanation.
but the researchers who believe that all the continents are moving on the surface of the earth also believe that South America Africa India and Australian continents are moving away form the central continent of Antarctica.
and the researchers believe that the Antarctica continents is surrounded by sea floor centre where new sea floor is formed and spreading toward the north therefore the southern continents which rest on the moving plate also moving towards the north i.e moving away from the central Antarctica.
but in this case unlike the longitude spreading the latitudes are having different length.
particularly the latitude near the south pole i.e just around the central Antarctica is smaller then the northern latitudes which is near the equator.
therefore if new sea floor is formed around the Antarctica as the researchers believed and moved towards the north then huge gap will be formed around the central continent of Antarctica.
therefore the newly formed sea floor can not carry huge continents and move along with huge continents as a single plate.
therefore this sea floor spreading model around the Antarctica is proved to be wrong as well as the notion of the moving of the southern continents also proved to be wrong.
particularly rock plate which is formed at the small circumference area can not have the strength to pushing the rock plate which is occupying larger surface area.therefore the said explanation i.e newly formed rock plate moving northward direction which is also said to be carrying the huge continents is not possible.