. | . |
When magma prevents volcanic eruptions by Staff Writers Geneva, Switzerland (SPX) Nov 29, 2017
A spectacular proof of our planet's activity, calderas are huge topographic depressions, similar to flat-bottomed craters, with a diameter of several tens of kilometres. They are formed by large volcanic eruptions, and sometimes experience an inflation of their floor of up to a kilometre, caused by magma injection. This well-known process, dubbed "caldera resurgence", has been observed several times and yet remains one of the least understood in volcanology. The enigmatic question was: Why after an eruption the arrival of new magma does not produce another major eruption but resurgence? A team of researchers from the University of Roma Tre, Italy, and the University of Geneva (UNIGE), Switzerland, shows that the non-erupted magma left after the caldera-forming eruption behaves as a "rubber sheet" that inhibits the rise to the surface of the newly injected magma. A research published in Nature Communications. A caldera forms when a magma chamber is partially emptied by a large eruption and its roof collapses producing a depression at the surface. After this catastrophic event, in a slow process that can last thousands of years, the caldera floor may start to lift disproportionately but no eruption follows. Resurgence does not immediately follow caldera formation, suggesting that it is not driven by the residual magma left in the reservoir after collapse, but rather by the injection of new magma.
The magma behaves as a rubber sheet The magma, hotter than the rocks surrounding the magma chamber, cools progressively and its viscosity increases. The higher viscosity of the left over magma, with respect to the newly injected magma, makes it behave as a rubber sheet stopping the propagation of the new magma to the surface. These results were corroborated by experiments. The left over magma was replaced by a silicone layer and the newly injected magma by less viscous vegetable oil. The contrast in viscosity between these two materials is equivalent to the contrast observed between the two magmas in nature. "Independently of the depth of the silicone layer, its presence always impede the propagation of the newly injected magma to the surface" - says Federico Galetto, researcher at the Department of Science of the University of Roma Tre. The model developed by the researchers provides a theoretical framework to account for the transition from magma eruption to accumulation. Valerio Acocella, associate professor at the Department of Eart Sciences of the University of Roma Tre, adds: "The process we discuss is essential not only to develop resurgence, but also for the formation of the magma reservoirs responsible for the largest eruptions on Earth."
Hamburg, Germany (SPX) Nov 30, 2017 The first observation of a super-hydrated phase of the clay mineral kaolinite could improve our understanding of processes that lead to volcanism and affect earthquakes. In high-pressure and high-temperature X-ray measurements that were partly conducted at DESY, scientists created conditions similar to those in so-called subduction zones where an oceanic plate dives under the continental crust. ... read more Related Links Universite de Geneve Bringing Order To A World Of Disasters When the Earth Quakes A world of storm and tempest
|
|
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. |