Ancient geologic events linked to earthquakes: Study

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Toronto, June 12 (IANS) Ancient geologic events may have left deep 'scars' that can play a crucial role in earthquakes, mountain formation, and other ongoing geomorphological processes on our planet, says a new study.

An international team of geologists has created super-computer models that suggest former plate boundaries could stay hidden deep beneath the Earth's surface. 

These multi-million-year-old geological structures, situated at sites away from existing plate boundaries, may trigger changes in the structure and properties at the surface in the interior regions of continents.

"This is a potentially major revision to the fundamental idea of plate tectonics," said study lead author Philip Heron from University of Toronto.

Heron, together with University of Aberdeen geologist Randell Stephenson, has proposed a "perennial plate tectonic map" of the Earth to help illustrate how ancient processes may have present-day implications, according to the study published recently in the journal Nature Communications.

"It's based on the familiar global tectonic map that is taught starting in elementary school," said co-author Russell Pysklywec, who is also chair of University of Toronto's department of earth sciences. 

"What our models redefine and show on the map are dormant, hidden, ancient plate boundaries that could also be enduring or 'perennial' sites of past and active plate tectonic activity," he added.

The team used Toronto's SciNet -- Canada's most powerful computer and one of the most powerful in the world -- to make numerical models of the crust and upper-mantle into which they could introduce ancient scar-like anomalies.

Using these models, the researchers found that different parts of the mantle below the Earth's crust may control the folding, breaking, or flowing of the Earth's crust within plates -- in the form of mountain-building and seismic activity -- when under compression.

In this way, the mantle structures dominate over shallower structures in the crust that had previously been seen as the main cause of such deformation within plates.

"The mantle is like the thermal engine of the planet and the crust is an eggshell above," said Pysklywec. "We're looking at the enigmatic and largely unexplored realm in the Earth where these two regions meet," he added.

The simulations show that mantle anomalies are generated through ancient plate tectonic processes, such as the closing of ancient oceans, and can remain hidden at sites away from normal plate boundaries until reactivation generates tectonic folding, breaking, or flowing in plate interiors.​

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