June 2016 – GEOLOGY – Ancient geologic events may have left deep ‘scars’ that can come to life and play a role in earthquakes, mountain formation and other ongoing processes on our planet, a new study which involved super-computer modeling of Earth’s crust and upper-mantle has found. This changes the widespread view that only interactions at the boundaries between continent-sized tectonic plates could be responsible for such events, researchers said. Scientists from University of Toronto (U of T) in Canada and the University of Aberdeen in the UK have created models indicating that former plate boundaries may stay hidden deep beneath the Earth’s surface.
These multi-million-year-old 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, researchers said. “This is a potentially major revision to the fundamental idea of plate tectonics,” said Philip Heron from U of T. Researchers have proposed a ‘perennial plate tectonic map’ of the Earth to help illustrate how ancient processes may have present-day implications. “It is based on the familiar global tectonic map that is taught starting in elementary school. 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,” said Russell Pysklywec from U of T.
To demonstrate the dominating effects that anomalies below the Earth’s crust can have on shallow geological features, researchers used SciNet – home to 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 these scar-like anomalies. They created an evolving “virtual Earth” to explore how such geodynamic models develop under different conditions. “For these sorts of simulations, you need to go to a pretty high-resolution to understand what is going on beneath the surface,” said Heron. “We modeled 1,500 kilometers across and 600 kilometers deep, but some parts of these structures could be just two or three kilometres wide. It is important to accurately resolve the smaller-scale stresses and strains,” he said.
Using these models, 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. They suggest that ancient geologic events may have left deep ‘scars’ that can come to life to play a role in earthquakes, mountain formation, and other ongoing processes on our planet. “Ultimately, this information could even lead to ways to help better predict how and when earthquakes happen. It is a key building block,” said the findings were published in the journal Nature Communications. –Deccan Chronicle