By IANS
New York : The movement of earth’s crust has long been thought to be a continuous process. But new research suggests that plate tectonic motions have occasionally stopped, and may do so again.
The research by geophysicists Paul Silver and Mark Behn suggests that the tectonic movements did stop at least once in earth’s geological history, a finding that could reshape people’s understanding of the planet.
Most of the geologic processes on earth – the formation of continents, the birth of volcanic island arcs, the opening and closing of ocean basins – are driven by tectonic plate motions and intimately linked to subduction, or the collision of two tectonic plates.
A majority of subduction occurs around the edges of the Pacific Ocean, which is slowly closing as the Atlantic Ocean opens. In roughly 350 million years, researchers estimate that the Pacific basin will be effectively closed and a new super-continent will be formed.
Closure of the Pacific basin could shut down most of earth’s capacity for subduction, unless the process begins somewhere else on the planet. However, there is no evidence that subduction is currently expanding or initiating anywhere else on the planet.
Although such a shutdown defies the prevailing wisdom about plate tectonics, Silver and Behn read the geologic evidence to suggest that just such a dramatic decrease in subduction happened about one billion years ago, after the formation of the super-continent Rodinia.
Their findings, in a paper entitled ‘Intermittent Plate Tectonics?’, have been published in the latest issue of the journal Science.
“The scientific community has typically assumed that plate tectonics is an active and continuous process, that new crust is constantly being formed while old crust is recycled,” said Behn.
“But the evidence suggests that plate tectonics may not be continuous. Plates may move actively at times, then stop or slow down, and then start up again.”