The movement of the tectonic plates works according to a chain reaction

An international group of geologists, including researchers from Ben Gurion and Tel Aviv University, discovered a connection between earthquakes in different parts of the world

Why do tectonic plates move and why do they change their movement? Until now, geologists have assumed that the changes in tectonic movements occur as isolated events that are unrelated, but an international study with the participation of Ben-Gurion University of the Negev has proven that these changes are related to each other and produce a tectonic chain reaction that continues over tens of millions of years. "We are now able to better understand the forces that drive processes such as the formation of mountains or volcanoes." The study was published in the journal Nature Geoscience.

In Earth's geological past, there were 'short' periods of a few million years during which many tectonic plates around the world suddenly changed their speed and direction of movement. Previous studies have indicated that the changes in motion could be caused by the collision of continents or as a result of intense volcanic activity on Earth's surface. Next to this assumption, the question arose whether these changes are related to each other? Now geologists have managed to find evidence to support this hypothesis.

Joint research for geologists from the University of Utrecht in the Netherlands, the Australian National University And Ben-Gurion University of the Negev analyzed the sequence of tectonic events of the plates that make up the solids in the world, step by step.

As in an old tape, the chronicle of the movements of the continents in the past is stored in the magnet of the basalt rocks that are at the bottom of the oceans and make up the oceanic crust (the shallowest six kilometers on Earth and are under the ocean floor). As soon as magma reaches the surface at the volcanic ridges located in the center of the oceans ("mid-ocean ridges"), it cools and the minerals acquire a magnet that is parallel in its direction to the Earth's magnetic field. The Earth's magnetic field has reversed its direction hundreds of times during geological history and as a result of the tectonic movements, the rocks (crust) move away from the ridges and create a symmetrical signature on both sides. In this way, the ocean rock magnet makes it possible to reconstruct the movement of the plates in the distant past.

 During the Late Cretaceous, between 83 and 126 million years ago, there were no reversals of the magnetic field. "In the ocean crust that was created during this period, the magnetic field everywhere pointed in the same direction, so that a region of magnetic silence was created," explained Prof. Van Hinsbergen, the research partner.

As a result, until recently it was impossible to reconstruct plate motion changes in this mysterious time interval. But about a decade ago he discovered Prof. Roy Granot, from the Department of Earth and Environmental Sciences at Ben-Gurion University of the Negev, that the rocks in the Pacific region in the middle of the Atlantic Ocean recorded sudden changes in the behavior of the magnetic field. "By applying the methods we normally use for magnetic reversals to changes in the 'magnetic noise', we were able to show for the first time that the tectonic changes occur as a chain reaction. One change in the movement of the plates causes additional changes that occur as a result and a sequence of tectonic events is created that continues over tens of millions of years", Prof. Granot noted. For example, the continent of Africa experienced a sharp rotation that caused a series of tectonic events, including an area into which oceans were eroded, in this case the Tethys Ocean.

"This is the first time that evidence of a tectonic chain reaction of the plates has been found. With this research, we analyzed a mechanism that explains why there are periods of time when the plates suddenly change direction and what the long-term effect of these changes is. The movements of the plates affect the formation of mountains, sea gates, ocean flow patterns, volcanic activity and even the global climate," said Dr. Gorer.

 The research group included: Professor Dow van Hinsbergen, and Dr. Daria Gurer from the University of Utrecht and the Australian National University and Professor Roi Granot from the Ben-Gurion University of the Negev. This research (No. 1923/21*) was supported by the National Science Foundation as well as by NWO Vici grant (865.17.001). 

More of the topic in Hayadan:

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