Science & Technology

First Solid Clues Uncovered to Start of Earth’s Supercontinent Cycle

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A graphical abstract of Earth’s supercontinents/supercratons. Credit score: Modified from D. A. D. Evans, Z. X. Li and J. B. Murphy, Geological Society, London, Particular Publications, 424, 1-14, March 2, 2016, https://doi.org/10.1144/SP424.12

Curtin College analysis has uncovered the primary stable clues concerning the very starting of the supercontinent cycle of Earth, discovering it was kick-started two billion years in the past.

Detailed in a paper printed in Geology, a staff of researchers from Curtin’s Earth Dynamics Analysis Group discovered that plate tectonics operated in a different way earlier than two billion years in the past, and the 600 million years supercontinent cycle seemingly solely began throughout the second half of Earth’s life.

Lead researcher Dr. Yebo Liu from Curtin’s Faculty of Earth and Planetary Sciences mentioned that the shift in plate tectonics marked a regime change within the Earth System.

“This regime change impacted on the eventual emergence of complicated life and even how Earth assets are fashioned and preserved,” Dr. Liu mentioned.

Pangea was the primary supercontinent scientists found early final century that existed some 300 million years in the past and lasted till the age of the dinosaurs. Geologists realized extra not too long ago that at the very least two older supercontinents existed earlier than Pangea up to now two billion years (Ga) in a 600 million 12 months cycle. However what occurred within the first 2.5 billion years of Earth’s historical past is anyone’s guess.”

“Our analysis was primarily testing two hypotheses – one is that the supercontinent cycle began prior to two billion years in the past. Alternatively, the traditional continents (known as cratons) solely managed to get collectively in a number of clusters known as supercratons, as a substitute of forming a singular supercontinent.”

To conduct their assessments, the Curtin researchers ventured into the hills east of Perth, Western Australia, an space often called the Yilgarn craton.

Dr Liu mentioned Yilgarn was a essential piece of the puzzle not solely as a result of it’s outdated, but in addition as a result of there are a collection of darkish rocks or dolerite dykes that recorded Earth’s historic magnetic area on the time that the rocks fashioned.

“By exactly relationship the rocks and measuring the samples’ magnetic document, utilizing a way known as paleomagnetism, we’re ready to reconstruct the place these rocks had been (relative to the magnetic North pole) after they fashioned,” Dr. Liu mentioned.

Co-author John Curtin Distinguished Professor Zheng-Xiang Li, from Curtin’s Faculty of Earth and Planetary Sciences, mentioned by analyzing their new information from Yilgarn, and evaluating it with information accessible globally for different cratons, one factor turned clear.

“It was clear that we will nearly rule out the existence of a long-lived single supercontinent earlier than two billion years in the past (2 Ga), though transient supercontinents might have existed,” Professor Li mentioned.

“Extra seemingly, there might have been two long-lived clusters of cratons, or supercratons, earlier than 2 Ga that had been geographically remoted from one another, by no means forming a singular supercontinent.”

Professor Ross Mitchell of the Chinese language Academy of Sciences, who was beforehand a member of Curtin’s Earth Dynamics Analysis Group, mentioned the analysis goes a way to fixing a long-standing thriller.

“The concept of a fair older supercontinent has been speculated about for years. However whereas it has been troublesome to show, it has additionally been troublesome to disprove,” Professor Mitchell mentioned.

Dr. Liu mentioned extra research now want to be accomplished.

“This research absolutely isn’t the ultimate phrase on the controversy, nevertheless it’s actually a step in the appropriate path and we’d like to accumulate information from much more related rocks to additional take a look at the hypotheses,” Dr. Liu mentioned.

Reference: “Archean geodynamics: Ephemeral supercontinents or long-lived supercratons” by Yebo Liu, Ross N. Mitchell, Zheng-Xiang Li, Uwe Kirscher, Sergei A. Pisarevsky and Chong Wang, 22 March 2021, Geology.

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