Hidden "Mantle Scars" Can Come To Life And Cause Earthquakes

White lines show active plate boundaries; yellow show the locations of potential mantle scars. Russell Pysklywec, Philip Heron, Randell Stephenson

Billions of years ago, the Earth was internally hotter than it is today. This meant that plate tectonic movements were comparatively more violent and energetic, volcanism was more powerful, and the collisions of plates were far more catastrophic.

Masses of crust rapidly compacted together managed to survive later continental break-ups, and these so-called “cratons” still exist today. The scars of their ancient tectonic activity may still remain, however, and this team of researchers wanted to know where they could be found. By using one of the most powerful super-computers available, they simulated a virtual Earth, inputting a range of geodynamic conditions in order to see how the crust and mantle interacted.

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The cycle of supercontinent formation and destruction – also known as the Wilson Cycle – cannot explain everything we see at the surface. In particular, intraplate deformation and LLSVPs (mantle plumes) cannot be effortlessly linked to the movement of tectonic plates alone. Russell Pysklywec, Philip Heron, Randell Stephenson

These models revealed that although the major tectonic activity, including earthquakes and mountain-building, happens on the known tectonic lines, long-dead tectonic activity would have left chasms within the deep crust at the center of tectonic plates. Although there is no evidence that these scars pose an immediate reactivation threat, they could be resurrected if a mantle plume emerges beneath them or the movement of the modern plates tear them open again.

Remarkably, the idea of earthquakes happening far from tectonic plate boundaries isn’t actually new. In one study, scientists discovered that parts of the upper mantle are falling off into the lower, more molten section; the upwelling of hotter, buoyant material designed to fill in these gaps are causing earthquakes in regions far from tectonic faults, such as in Washington D.C just a few years ago.

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