FYFD

Tag: geophysics

  • Featured Video Play Icon

    Salt Affects Particle Spreading

    Microplastics are proliferating in our oceans (and everywhere else). This video takes a look at how salt and salinity gradients could affect the way plastics move. The researchers begin with a liquid bath sandwiched between a bed of magnets and electrodes. Using Lorentz forcing, they create an essentially 2D flow field that is ordered or chaotic, depending on the magnets’ configuration. Although it’s driven very differently, the flow field resembles the way the upper layer of the ocean moves and mixes.

    The researchers then introduce colloids (particles that act as an analog for microplastics) and a bit of salt. Depending on the salinity gradient in the bath, the colloids can be attracted to one another or repelled. As the team shows, the resulting spread of colloids depends strongly on these salinity conditions, suggesting that microplastics, too, could see stronger dispersion or trapping depending on salinity changes. (Video and image credit: M. Alipour et al.)

    Fediverse Reactions
  • Flooding the Mediterranean

    Flooding the Mediterranean

    Nearly 6 million years ago, the Mediterranean was cut off from the ocean and evaporated faster than rivers could replenish it. This created a salty desert that persisted until about 5.3 million years ago. One hypothesis — the Zanclean megaflood — suggests that the Mediterranean refilled rapidly through an erosion channel near the Strait of Gilbraltar. A new study bolsters the concept by identifying geological features near Sicily consistent with the megaflood.

    The team point to a grouping of over 300 ridges near the Sicily Sill, once a land bridge dividing the eastern and western Mediterranean and now underwater. The ridges are layered in debris but aren’t streamlined, suggesting they were rapidly deposited by turbulent waters, and date to the period of the proposed flooding. For more on the Zanclean Flood, check out this older post. (Image credit: R. Klavins; research credit: A. Micallif et al.; via Gizmodo)

    Fediverse Reactions
  • Predicting Landslide Speeds

    Predicting Landslide Speeds

    Knowing what speed a landslide will reach helps us predict how much damage they can cause. That speed depends on many factors: the steepness of the terrain, the sliding distance, the thickness of the flowing layer, and the type of grains making up the flow. Researchers found that predictions from previous studies often underestimated the speeds reached by thicker flows. Through laboratory experiments with grains of different shapes, a team found that those models mistakenly assumed a fully-developed flow — in other words, one where the grains have reached a constant final speed. While spherical grains reach that state over a short sliding distance, that’s not the case for other grains.

    Instead, the team used their results to build a new predictive model for landslide speeds. This one still depends on incline angle and flow thickness, but it also uses a dynamical friction coefficient to describe the granular material and capture how the flow’s speed varies with distance down the incline. (Image credit: W. Hasselmann; research credit: Y. Wu et al.; via APS News)

    Fediverse Reactions
  • Tracking Meltwater Through Flex

    Tracking Meltwater Through Flex

    Greenland’s ice sheet holds enough water to raise global sea levels by several meters. Each year meltwater from the sheet percolates through the ice, filling hidden pools and crevasses on its way to draining into the sea. Monitoring this journey directly is virtually impossible; too much goes on deep below the surface and the ice sheet is a precarious place for scientists to operate. So, instead, they’re monitoring the bedrock nearby.

    Researchers used a network of Global Navigation Satellite System (GNSS) stations like the one above to track how the ground shifted and flexed as meltwater collected and moved. They found that the bedrock moved as much as 5 millimeters during the height of the summer melt. How quickly the ground relaxed back to its normal state depended on where the water went and how quickly it moved. Their results indicate that the water’s journey is not a short one: meltwater spends months collecting in subterranean pools on its way to the ocean — something that current climate models don’t account for. Overall, the team’s results indicate that there’s much more hidden meltwater than models predict and it spends a few months under the ice on its way to the sea. (Image credit: T. Nylen; research credit: J. Ran et al.; via Eos)

    Fediverse Reactions
  • The Underwater Effects of Volcanoes

    The Underwater Effects of Volcanoes

    Although volcanoes are typically located in or near the ocean, we’ve spent relatively little effort studying how eruptions affect the marine environment. A recent research voyage aimed to change that by studying the Patagonian Sea near the site of the 2008 Chaitén eruption. Marked by massive ashfalls that, when mixed with heavy rains, created huge mudslides, the 2008 eruption was the Chaitén volcano’s first in 9,000 years.

    The researchers mapped the seafloor near the volcano, finding massive dunes shaped by strong currents. Using a remotely operated vehicle, the team surveyed and sampled the seafloor, collecting sediments reaching back some 15,000 years. They also located ash from the 2008 eruption over 24 kilometers from the volcano. With their data, they hope to understand both how the recent eruption changed the marine environment as well as how older eruptions affected the area. (Image credits: volcano – USGS, dunes – Schmidt Ocean Institute; see also Schmidt Ocean Institute; via Ars Technica)

    Composite image showing the massive underwater dunes off the coast.
    Composite image showing the massive underwater dunes off the coast.

    P.S. – This Friday, January 24th from 12 to 1:30pm Eastern I’m moderating a panel discussion on the Traveling Gallery of Fluid Motion and how art and science can work together in public outreach. Register here to join. It’s free!

    Fediverse Reactions
  • Tracking Coastal Sediment Loss

    Tracking Coastal Sediment Loss

    Shorelines rely on an influx of sediment to counter what’s lost to erosion by waves and currents. But tracking that sediment flux is challenging in coastal regions where salt, waves, and storms batter delicate instruments. Instead, researchers have turned to remote sensing through high-resolution satellites like Landsat to monitor these areas. Researchers built an algorithm to analyze coastal imagery, validated with local sediment measurements; once built, they deployed it in a free tool that lets anyone build a 40-year timeline of a coastal area’s sediment history.

    Looking at thousands of sites around the world, the team found coastal sediment is on the decline, especially along sandy and muddy coastlines. Where has the sediment gone? It’s likely that human-built infrastructure — both on coasts and upstream along rivers — is disrupting the natural flow of sediments that would replenish these regions. (Image credit: NASA; research credit: W. Teng et al.; via Eos)

  • A New Mantle Viscosity Shift

    A New Mantle Viscosity Shift

    The rough picture of Earth’s interior — a crust, mantle, and core — is well-known, but the details of its inner structure are more difficult to pin down. A recent study analyzed seismic wave data with a machine learning algorithm to identify regions of the mantle where waves slowed down. These shifts in seismic wave speed occur in areas where the mantle’s viscosity changes; a higher viscosity makes waves travel slower.

    The team found seismic wave speed shifts at depths of 400 and 650 kilometers, corresponding to known viscosity changes. But they found shifts at 1050 and 1500 kilometers, as well — the first time anyone has shown a global viscosity shift at those depths. Their analysis suggests a higher viscosity in this mid-mantle transition zone, which could affect how tectonic plates, which rely on these slow mantle flows, move. (Image credit: NASA; research credit: K. O’Farrell and Y. Wang; via Eos)

  • Glacial Tributaries

    Glacial Tributaries

    Just as rivers have tributaries that feed their flow, small glaciers can flow as tributaries into larger ones. This astronaut photo shows Siachen Glacier and four of its tributaries coming together and continuing to flow from the top to the bottom of the image. The dark parallel lines running through the glaciers are moraines, where rocks and debris are carried along by the ice. Those seen here are medial moraines left by the joining of tributaries. When glaciers retreat, moraines are often left behind, strewn with sediment that ranges from the fine powder of glacial flour all the way to enormous boulders. (Image credit: NASA; via NASA Earth Observatory)

    Fediverse Reactions
  • A Magnetic Tsunami Warning

    A Magnetic Tsunami Warning

    Tsunamis are devastating natural disasters that can strike with little to no warning for coastlines. Often the first sign of major tsunami is a drop in the sea level as water flows out to join the incoming wave. But researchers have now shown that magnetic fields can signal a coming wave, too. Because seawater is electrically conductive, its movement affects local magnetic fields, and a tsunami’s signal is large enough to be discernible. One study found that the magnetic field level changes are detectable a full minute before visible changes in the sea level. One minute may not sound like much, but in an evacuation where seconds count, it could make a big difference in saving lives. (Image credit: Jiji Press/AFP/Getty Images; research credit: Z. Lin et al.; via Gizmodo)

  • Erie Algal Bloom

    Erie Algal Bloom

    Blue-green algae bloom in Lake Erie’s summer conditions. Unfortunately for those looking to spend summer on the water, the dominant organism in this bloom produces a toxin that “can cause liver damage, numbness, dizziness, and vomiting.” Bloom season can last from late June into October, depending on the how many nutrients get washed into the lake and when wind mixes the lake water in the fall. A new hyperspectral instrument aboard NASA’s PACE spacecraft will identify bloom species from space, helping scientists track, understand, and predict blooms like these. (Image credit: W. Liang; via NASA Earth Observatory)