. | . |
What goes down, must come up: Stirring things up in the Earth's mantle by Staff Writers Leicester UK (SPX) May 15, 2017
New insights into the convection patterns of the Earth's mantle and its chemical makeup have been revealed by a researcher from the University of Leicester. The new findings suggest that the mantle does not flow ubiquitously, as has been previously thought - and that it is instead divided into two very large domains that convect only within themselves, with little evidence of them mixing together. The research, led by Dr Tiffany Barry from the University of Leicester, Department of Geology and published in the journal Scientific Reports, Nature, suggests that one of these domains is found under the Pacific Ocean while the other exists outside of it. The research suggests that upper mantle material flows to lower parts of the mantle when it reaches a subduction zone, where one tectonic plate descends beneath another one. This descending slab of material acts as a sort of curtain, preventing upper mantle material mixing all the way around the globe and keeping the two domains separate. Dr Barry explained: "One of the ways our planet is unique is in the amazing way it has mobile plates at the surface that move and jostle about over time. This movement of the plates results in the process we call plate tectonics, and no other planet we know shows evidence of this process. Why or how plate tectonics started on this planet is not understood, but it has been utterly essential in the production of the crust and oceans that we recognise as Earth today. What is also not well constrained is what effect plate tectonics has on the internal workings of the Earth. "We have found that when mantle material reaches the bottom of the mantle, at the outer core, it does not spread out and go anywhere around the core, but instead returns to the same hemisphere of the globe from where it came. We have modelled this dominantly up-down motion of convection and found that it can persist for 100's millions of years. "On the basis of past plate motions and geochemical evidence, we speculate that this process of mantle convection could have been a dominant process since at least 550 million years ago, and potentially since the start of plate tectonics." The researchers combined spherical numerical computer models (3D finite element modelling) with the best available reconstructions of how Earth's plates have moved over the past 200 million years to track mathematical particles placed at different depths of the modelled mantle. With these models they examined where the mantle freely moves to during the history of plates moving around at the surface. Having tracked where particles flow in the models, the team then examined chemical isotope evidence from past ocean basins, which are a good analogy for the composition of the upper mantle in the past. With this data they were able to test whether former ocean basins, that are no longer present, had the same or different composition to subsequent basins that formed geographically in the same region of the globe. Dr Barry added: "I'm incredibly excited by this work; it has been a research question I've been pondering for nearly two decades. It feels like a real privilege to have been able to piece together a robust and convincing model that can explain the feature of the chemical differences in ocean floor crust. "This new research overturns our understanding of how the inside of the earth convects and stirs, and how it is divided up, and for the first time explains observations that were first noted in the late 1980s."
Research Report: 'Whole-mantle convection with tectonic plates preserves long-term global patterns of upper mantle geochemistry'
Beijing, China (SPX) May 10, 2017 North China is one of the areas of strong earthquake activity on the Chinese mainland. In the 1960s~1970s, North China has undergone the 1966 Xingtai Ms7.2, 1969 Bohai Ms7.4, 1975 Haicheng Ms7.3 and 1976 Tangshan Ms7.8 earthquake, causing great losses to people's life and property, where the Tangshan earthquake caused casualties amounted to 240 thousand. In the past 50 years, Chinese seism ... read more Related Links University of Leicester Tectonic Science and News
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |