AP, Categories: Local San Diego News, National & International News Mattis expected to send hundreds of troops to border AP FacebookTwitter WASHINGTON (AP) — Defense Secretary Jim Mattis is expected to sign an order as early as Thursday sending 800 or more troops to the southern border to support the Border Patrol, a U.S. official said.Mattis is responding to a request from President Donald Trump, who says he’s “bringing out the military” to address what he’s calling a national emergency at the border.The U.S. official was not authorized to speak publicly because not all details of the military arrangement had been worked out, and so spoke on condition of anonymity.The additional troops are to provide what one official described as logistical support to the Border Patrol. This would include a variety of things such as vehicles, tents and equipment, and perhaps medical support. It was not immediately clear how many, if any, of the extra troops would be armed. Because they would not be performing law enforcement duties they would not be in violation of the Posse Comitatus Act, which prohibits the federal government from using the armed forces in a domestic police role.There already are about 2,000 National Guard troops assisting at the border under a previous Pentagon arrangement.A small group of Honduran migrants trying to reach the U.S. border walk along train tracks in Trancas Viejas, Veracruz state, Wednesday, Oct. 24, 2018. As a caravan of thousands of Central Americans renewed their slow march toward the U.S. on Wednesday, others chose to travel in smaller groups following routes well-worn by decades of migrants fleeing poverty and violence.(AP Photo/Rebecca Blackwell) October 25, 2018 Posted: October 25, 2018
Citation: Diamond inclusions suggest free flowing water at boundary between upper and lower mantle (2018, March 9) retrieved 18 August 2019 from https://phys.org/news/2018-03-diamond-inclusions-free-boundary-upper.html More information: O. Tschauner et al. Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle, Science (2018). DOI: 10.1126/science.aao3030AbstractWater-rich regions in Earth’s deeper mantle are suspected to play a key role in the global water budget and the mobility of heat-generating elements. We show that ice-VII occurs as inclusions in natural diamond and serves as an indicator for such water-rich regions. Ice-VII, the residue of aqueous fluid present during growth of diamond, crystallizes upon ascent of the host diamonds but remains at pressures as high as 24 gigapascals; it is now recognized as a mineral by the International Mineralogical Association. In particular, ice-VII in diamonds points toward fluid-rich locations in the upper transition zone and around the 660-kilometer boundary.Press release A team of researchers from the U.S., China and Canada has found evidence in diamonds of free-flowing water in the boundary between Earth’s upper and lower mantle. In their paper published in the journal Science, the group describes analyzing inclusions in diamonds spewed from volcanoes and what they found. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The researchers were looking for molecular forms of carbon dioxide as part of carbon cycling in the Earth’s mantle when they came across evidence of something else. They had collected diamonds spewed from volcanoes (or pushed to the surface by other geologic activity) in Zaire, China, Sierra Leone and other locations in southern Africa, and were studying them by bouncing X-rays off the diamonds’ inclusions, when they came across samples of ice VII—a form of ice that does not occur naturally at the surface. The find was significant, because ice VII forms at very high pressure—approximately the amount of pressure found at depths of 610 to 800 kilometers beneath the Earth’s surface. This, the team notes, suggests that water must have been freely flowing at such depths to form the inclusions they observed. Such depths, they further note, fall into the transition zone in the mantle, a part of the Earth’s interior that is still a source of mystery.Prior research has shown that the mantle is made up mostly of hot rock under a lot of pressure. It has a lower layer, closest to the core, a transition layer, and an upper layer that eventually meets the crust. Prior research has also shown that the upper mantle has some water, which hints that there may also be water in the transition layer. The diamonds the researchers were studying would have been encased in liquid somewhere in the transition zone. The high temperatures there would not have allowed them to crystallize, however—it was only as they moved to the surface that crystallization would have occurred. The high pressure would have been maintained inside the diamond, but the temperature would have dropped dramatically. The idea of water moving around in the transition layer is intriguing, the team reports, because it has implications for tectonic plate shifting. Using Argonne’s Advanced Photon Source, researchers identified a form of water known as Ice-VII, which was trapped within diamonds that crystallized deep in the Earth’s mantle. Credit: University of Chicago.