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      This Yellowstone hot spring’s rhythmic thump makes it a geo-thermometer

      news.movim.eu / ArsTechnica · Friday, 10 March, 2023 - 19:23 · 1 minute

    The vibrating water surface of Doublet Pool in Yellowstone National Park. Credit: Jamie Farrell/University of Utah

    Yellowstone National Park is most famous for Old Faithful , a geyser with fairly predictable periodic eruptions that delight visiting tourists. But it's also home to many other geothermal features like Doublet Pool , a pair of hot springs connected by a small neck with the geothermic equivalent of a pulse. The pool "thumps" every 20-30 minutes, causing the water to vibrate and the ground to shake. Researchers at the University of Utah have measured those thumping cycles with seismometers to learn more about how they change over time. Among other findings, they discovered that the intervals of silence between thumps correlate with how much heat is flowing into the pool, according to a new paper published in the journal Geophysical Research Letters.

    “We knew Doublet Pool thumps every 20-30 minutes,” said co-author Fan-Chi Lin , a geophysicist at the University of Utah. “But there was not much previous knowledge on what controls the variation. In fact, I don’t think many people actually realize the thumping interval varies. People pay more attention to geysers.”

    Yellowstone's elaborate hydrothermal system is the result of shallow groundwater interacting with heat from a hot magma chamber. The system boasts some 10,000 geothermal features, including steam vents (fumaroles), mud pots, and travertine terraces (chalky white rock), as well as geysers and hot springs.

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      Mathematicians may have unlocked the secret of how “stone forests” form

      Jennifer Ouellette · news.movim.eu / ArsTechnica · Wednesday, 16 September, 2020 - 11:54 · 1 minute

    The Stone Forest (Shilin) in China

    Enlarge / The Stone Forest (Shilin) in China's Yunnan Province may be the result of solids dissolving into liquids in the presence of gravity, producing natural convective flows.

    There are many wondrous geologic formations in nature, from Giant's Causeway in Ireland to Castleton Tower in Utah, and the various processes by which such structures form is of longstanding interest for scientists. A team of applied mathematicians from New York University has turned its attention to the so-called "stone forests" common in certain regions of China and Madagascar. These pointed rock formations, like the famed Stone Forest in China's Yunnan Province, are the result of solids dissolving into liquids in the presence of gravity, which produces natural convective flows, according to the NYU team. They described their findings in a recent paper published in the Proceedings of the National Academy of Sciences.

    Co-author Leif Ristroph told Ars that his group at NYU's Applied Math Lab became interested in studying stone forests (technically a type of karst topography ) by a somewhat indirect route. They were using simulations and experiments to explore the interesting shapes that evolve in landscapes due to a number of "shaping" processes, most notably erosion and dissolving.

    "We first discovered the spikes formed by dissolution when we left candy in a water tank and came back later to find a needle-like spire," he said. "The grad student, first author Mac Huang, even accidentally cut himself when he was admiring the shape. This drew us into the problem, and we were very excited when we realized the connection to stone pinnacles and stone forests, which have been quite mysterious in their development. We hope our experiments tell a simple 'origin story' behind these landforms."

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      How “St. Elmo’s fire” could help protect aircraft from lightning strikes

      Jennifer Ouellette · news.movim.eu / ArsTechnica · Thursday, 20 August, 2020 - 10:45 · 1 minute

    A passenger jet is gloriously silhouetted by a lightning storm.

    Enlarge / MIT scientists think the corona discharge known as "St. Elmo's fire" could help reduce the risk of aircraft being struck by lightning during thunderstorms. (credit: Anton Petrus/Getty Images )

    The electrical phenomenon known as St. Elmo's fire manifests during strong thunderstorms as a flash of blue light, usually at the tips of electrically conductive structures like cell phone towers, telephone poles, and ship masts—which is how it got its name, in honor of the patron saint of sailors, St. Erasmus of Formia. On the ground, St. Elmo's fire glows more brightly in windy conditions because the wind helps further electrify the surrounding air.

    But MIT scientists have discovered that wind has the opposite effect on ungrounded structures such as airplane wings and turbine blades, according to a recent paper in the Journal of Geophysical Research: Atmospheres. They discovered this while investigating the possibility of using St. Elmo's fire to control the electrical charge of an aircraft, thereby helping protect it from lightning strikes.

    St. Elmo's fire is not a form or lightning; it's essentially a continuous electric spark known as a corona discharge, like the glow of a neon sign. The friction that builds up in storm clouds gives rise to an electric field extending to the ground. If it's strong enough, the friction breaks apart surrounding air molecules, ionizing the air to produce a plasma (charged gas). All the excess electrons knock the plasma molecules into an excited state, which then emit photons to produce that telltale glow. The color of the glow depends on the type of gas being ionized. Since Earth's atmosphere is primarily made up of nitrogen and oxygen, the glow takes on a blue or violet hue.

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