Scientists Utrecht University explain what seemed theoretically impossible
What the Pacific Ocean and the Big Bang have in common
The Pacific Plate, the largest tectonic plate on earth, didn’t exist once and developed from a single point – just like the Big Bang. Current models and reconstructions however, suggest that theoretically this was impossible. New reconstructions from earth scientists at Utrecht University now explain and prove how the Pacific Plate developed with a 'Big Bang'. Their results, published in Science Advances on 27 July 2016, are leading to a paradigm shift in plate tectonics.
The Pacific Ocean is the largest ocean in the world, connecting the western coast of the American continent with the eastern coast of Asia. Almost the entire ocean is located on a single tectonic plate, the Pacific Plate, the boundaries of which stretch from Japan to California and from Alaska to Antarctica. One hundred and ninety million years ago the earth’s mainland still consisted of a single supercontinent, and this gigantic plate did not yet exist.
Three separate drifting plates
Geomagnetic research shows that the Pacific plate developed due to three separate drifting plates. The hole that opened up in the middle of the three-way intersection was filled with molten rock from below. The problem is that according to current theories, this is not possible.
Solution inspired by textbook
PhD candidate Lydian Boschman and her supervisor Douwe van Hinsbergen at Utrecht University now have found the solution for this paradox. Surprisingly, their solution was inspired by a textbook written in the 1980s. This book, used in the Earth Sciences Bachelor’s programme, sets out the different ways in which plate boundaries can meet in a tectonic three-way intersection. Boschman and van Hinsbergen realised that one of these explained precisely how the Pacific Plate developed.
An unstable three-way intersection
“Scientists originally thought that three mid-ocean ridges came together in the three-way intersection between the plates,” explains Van Hinsbergen. “This created a hole that filled up with molten rock from below. But that rock was attached to the existing plates and would never have formed a separate tectonic plate, as happened with the Pacific Plate."
Faults instead of ridges
"What we realised was that a new plate only emerges when three ‘transform faults’ rather than three mid-ocean ridges, meet. In such cases, the plates move along one other, as with the San Andreas Fault. Such a situation is unstable, and as soon as it occurs, a hole emerges, just as it did when the Pacific Plate developed”, continues Van Hinsbergen.
Boschman adds: “What’s more, we saw that in order for such an unstable situation to occur, there must first have been a subduction zone, in which one plate slid under another. A subducted plate can be tracked down in the deep mantle,. We found it off the coast of Costa Rica, at a depth of 2,000 kilometres. So now we not only know how the Pacific Plate formed, but also where it formed and what the plates under the ocean around the supercontinent of Pangaea looked like before the Pacific Plate was there.”
A hidden gem
Boschman and Van Hinsbergen sent their findings to Science Advances. Their publication is mainly based on a well-founded theoretical story and an insight that, surprisingly enough, had never come to light. This prompted one of the reviewers to write: ”This is one of those rare cases, where a discovery could be made simply by an elegant thought. It is like a gem that lay hidden for almost 50 years after discovery of plate tectonics and was finally unearthed. Or, to use another metaphor, it is like peeking before the Big Bang when the Pacific Plate (not the whole universe, though) was only one point.”
“On the enigmatic birth of the Pacific Plate within the Panthalassa Ocean”L.M. Boschman, D.J.J. van HinsbergenScience Advances 27 juli 2016, DOI:10.1126/sciadv.1600022
Magnetic anomalies on the Pacific Plate show that the plate developed around 190 million years ago in the form of a small triangle. Boschman and Van Hinsbergen show that this triangle developed in an unstable three-way intersection after a phase of subduction. Relics of subduction in the super ocean around Pangaea now lie along the boundaries in the given fields.