(Visited 112 times, 1 visits today)FacebookTwitterPinterestSave分享0 The national park signs may need updating.Arches National ParkNatural sandstone arches occur in many parts of the world, most notably in Arches National Park in eastern Utah. Visitors, upon reading the confident-sounding interpretive signs describing arch formation, might be surprised to learn that the origin of these structures is not fully understood. In a recent paper in Nature Geoscience, researchers from the Czech Republic who ran some new lab experiments imply that prior theories are incomplete, if not wrong:Weathering and erosion of sandstone produces unique landforms such as arches, alcoves, pedestal rocks and pillars. Gravity-induced stresses have been assumed to not play a role in landform preservation and to instead increase weathering rates. Here we show that increased stress within a landform as a result of vertical loading reduces weathering and erosion rates, using laboratory experiments and numerical modelling. We find that when a cube of locked sand exposed to weathering and erosion processes is experimentally subjected to a sufficiently low vertical stress, the vertical sides of the cube progressively disintegrate into individual grains. As the cross-sectional area under the loading decreases, the vertical stress increases until a critical value is reached. At this threshold, fabric interlocking of sand grains causes the granular sediment to behave like a strong, rock-like material, and the remaining load-bearing pillar or pedestal landform is resistant to further erosion.The new theory is summarized in the BBC News. In addition, Smithsonian Magazine has an embedded video clip of the experiments.In the authors’ view, gravity is the arch-hero, not the arch-villain. The gravitational load causes a kind of self-organizing system: the sand grains lock together in the pillars, resisting erosion. Eventually, of course, erosion wins, and the structure falls. It’s not clear if they can generalize this process to all arches. They experimented with a particular sand in their home country. “Critically, the sandstone from Strelec doesn’t contain cementing minerals that help bind the sand particles together,” the Smithsonian article says. “Instead, the authors found that the stress put on the sandstone causes minerals to interlock and hold the rock together.” It sounds like this is the best-case scenario to test the idea, because cementing materials would presumably increase the resistance to erosion in the pillars. Whether this applies to the Entrada Sandstone in Arches National Park is not clear; it also would not seem to apply to granite arches, as pictured below.Mobius Arch (granite) by David CoppedgeWhatever its merits, this new theory turns the old one on its head: “We should not say erosion or weathering carved the forms, as it was the stress field which give the forms the shape,” lead author Jiri Bruthans asserts in the Smithsonian article. “Erosion processes are mere tools controlled by stress.” The BBC quotes Bruthans comparing the stress field to Michelangelo. “The stress field is the master sculptor – it tells the weather where to pick.”Not much is said in any of the articles about how long it takes for arches to form. The Smithsonian says:The Czech team wanted to take a different approach. While doing fieldwork in Strelec quarry in the Bohemian Cretaceous Basin, they noticed that small arches and pillars—only about 2 feet high at most—formed out of the sandstone over mere months or years, rather than the millennial time scales associated with large geologic architecture.The BBC News, though, without a reference, says “The process had proved difficult to study, because natural slabs of sandstone erode over millions of years.”Landscape Arch, by David CoppedgeCreationists like Michael Oard have shown how just a few centuries since the Flood are sufficient (Creation.com, 2010) to form arches. He quotes secular authors who estimate only tens of thousands of years, not millions, for their formation; in fact, Oard argues, too much time is problematic: the arches should be long gone after even tens of thousands of years. Dr. Andrew Snelling, creation geologist, agrees, discussing sandstone arches briefly in the latest Answers Research Journal from AiG (July 2014). “What the park rangers won’t tell you,” Snelling says, is that 43 sandstone arches have collapsed since 1970. “Their loss is a sober reminder how delicate—and recent—these formations are,” he ends, after providing a Flood model for their formation. “Rapid processes created them and are now destroying them.”The Nature Geoscience paper is not clear on timeframes, so it is not clear the new theory can speak to the age issue. For the huge arches that were not observed forming, one can only estimate, considering variables and unknowns. Did arches form under steady-state processes vs one-time processes (like the Flood)? What were historical rainfall and wind patterns? You can’t look at erosion in a desert today and simply assume it’s always been so slow. It’s possible, in fact, to calculate reasonable upper limits on age of arches by taking conservative erosion rates today, and seeing how far back they can be extrapolated. If those rule out the “millions of years” interpretation, they show old ages to be a philosophical bias, not a conclusion from the evidence.Two other conclusions can be drawn from this story, though. One is the use of arches for design inference. What’s the difference between Landscape Arch pictured above, and the St. Louis Arch? Clearly the former is natural, and the latter intelligently designed. Beyond intuition, how can we tell? Use of such pithy examples can help teachers convey the principles of intelligent design. (Note: Comparing stress fields to Michelangelo is a personification fallacy.)The other conclusion is that scientific theories are at best tentative, especially when they try to speak of the unobservable past. The new theory is partly empirical, because these scientists were able to reproduce some features in the lab. But can one really scale up a small lab model by several orders of magnitude? Other factors might intrude at that level. For what it’s worth, the new theory overturns decades of thought and assumption about how these beautiful structures form, reminding us that science is, at best, a fallible human enterprise. Remember this story when you read the authoritative-sounding National Park signs.
RELATED ARTICLES Is This Building Passivhaus-Certified? Passivhaus Homes are Extremely Tight and Energy-Efficient Chris Straka, principal at Vert Design in Ottawa, Canada, apparently didn’t intend to meet the Passivhaus standard when he built his three-story duplex in the city’s Edinburgh neighborhood. Straka had consulted on dozens of green residential projects before starting his own company in 2006, and the main goal on this one, an infill project known as Rideau Residences (which overlooks the Rideau River), was to stay on budget while applying green building principals to most aspects of the project, from the deconstruction of a preexisting building on the lot to the reuse and recycling of materials to the implementation of conservation and energy efficiency measures in the new building. Ross Elliott, owner of Homesol Building Solutions, which offers Passivhaus consulting and certification in the Ottawa area, points out on his company’s website that colleagues told Straka that trying to build the duplex to the Passivhaus standard in the southeastern Ontario climate would be financially impractical. So he aimed instead for LEED for Homes Platinum certification, used conventional materials available in Canada, and tended to construction details as best he could to make the building energy efficient. He spent about $251 U.S. per square foot, which, he noted, is about 10% above the cost of a typical custom project in the Ottawa area. Backing into Passivhaus certificationStraka hired Ross to evaluate the energy efficiency of the building, whose two units each offer about 1,500 sq. ft. living space, and the two discovered it performed to the Passivhaus standard. “My goal was to build a building I could be proud of, not necessarily to build a Passive House,” Straka said, but added: “I knew that a very high performing building could be created using Canadian materials and mechanical systems.”The project, which Ross says is the first residential project in Canada to earn Passivhaus certification (see our story on Austria Passive House), also includes radiant-heat floors, a geothermal heat pump to supplement the building’s heat recovery ventilator, room for a cistern for rainwater collection, and a 1,200-sq.-ft. green roof with 12 in. of soil. A solar power system will be installed in the spring. According to the Vert Design website, the building has in fact been certified LEED Platinum. The website includes a slide show featuring many of the images highlighted here, as well as floor plans.
Yuvraj SinghCricketer Yuvraj Singh is likely to campaign for the BJP in the forthcoming Assembly elections in Haryana, sources said on Friday.The decision, sources said, was taken in a meeting Yuvraj had with BJP president Amit Shah in New Delhi on Friday.The cricketer from Chandigarh is considered to be popular in Haryana, where the BJP hopes to topple the two-time chief minister Bhupinder Singh Hooda of the Congress.Elections to the Maharashtra and Haryana Assembly will be held in a single phase on October 15 and the counting of votes will be done on October 19, the Election Commission announced on Friday.For the beleagured Congress, the upcoming polls in the two states currently ruled by it are an opportunity to make a comeback and shed its losing streak after the Lok Sabha humiliation when the party was reduced to an all-time low 44 seats.The Assembly elections, to be held shortly after the BJP’s spectacular victory in the Lok Sabha polls in May, will also check if the Narendra Modi wave still persists or has subsided.The Maharashtra Assembly has 288 seats while Haryana has 90.
Puel led Southampton to the League Cup final in February, but a 3-2 defeat to Manchester United ended his hopes of silverware and was followed by a woeful run of results in the run-in.Southampton won only one of their final eight league games, scoring just one goal in their last five home matches. They finished eighth in the table with their lowest points tally in four years.”Southampton Football Club can today confirm that it has terminated the contract of Claude Puel with immediate effect,” the club said in a statement.”Everyone at Southampton would like to express our thanks to Claude for his hard work and commitment this year.”Following the departure of Ronald Koeman to Everton, the 55-year-old Puel joined the club last June, after spending four years at French side Nice.The club had finished sixth under Koeman in 2015-16, but Puel’s league results were mixed throughout the campaign.He did enjoy success in the League Cup, however, eliminating Arsenal in the quarter-finals, before beating Liverpool home and away in the semi-final to get to Wembley.Their run was halted in the final, however, as United’s Zlatan Ibrahimovic scored twice, including an 87th-minute winner.”The highlight of the season was a memorable day at Wembley in the EFL Cup final, a day our fans will always treasure,” Southampton added in their statement.Former Southampton great Matt Le Tissier told Sky Sports that it was Puel’s failure to entertain fans that ultimately cost him his job.”I think the main sticking point was the lack of goals and the lack of entertaining football,” Le Tissier said.advertisement”No goals in the last five home games was a big factor. I am afraid that was what cost him his job.”There is a lot of sympathy when you look at the eighth-place finish and cup final. On paper, it doesn’t look a bad season, but if you have watched a lot of games this season, it has been a backward step.”The club said the search for a new manager was already underway and they were confident of finding the right fit for the club’s “long term vision”.Former Borussia Dortmund boss Thomas Tuchel was the early bookmakers’ favourite to replace Puel.
Scores of students are expected to participate in the annual Youth Forum, scheduled for Friday (November 2) at the St. Andrew Parish Church Hall, 16 Ellesmere Road. The event, organised by the National Child Month Committee (NCMC), will get underway at 9:00 a.m. To be held under theme: ‘Jamaica 50: Let’s Celebrate Our Children,’ the forum will include presentations from the Wolmer’s Girls and Penwood High Schools on the topic:‘Care and Protection for our Children during the Past 50 years’, while St. George’s College and Ardenne High School will be looking at the topic: ‘Recognition and Celebration of the Achievements of Our Children during the Past 50 Years’. Minister of Youth and Culture, Hon. Lisa Hanna, is schedule to bring greetings, while Principal of Wolmer’s School for Girls, Colleen Montague, will be the guest speaker. The annual Youth Forum is one of several activities organised by the NCMC to mark Child Month. It provides an avenue for children to voice their views on issues that affect them. “Children should be encouraged to express their ideas about issues that affect them and the environment must be created for children to learn about their rights and responsibilities and also how to overcome challenges that impede their success,” said Chair of the NCMC, Dr. Pauline Mullings, in an interview with JIS News. Initially a Child Month activity in May, the Youth Forum was moved to November as the NCMC is committed to organising year-long activities geared towards the nation’s children as well as for the observance of National Youth Month. The NCMC, instituted in 1953, brings together a number of agencies working with and on behalf of children in an effort to focus on their needs, and heighten public awareness on the relevant issues affecting the nation’s children.