FYFD

Tag: volcano

  • Lava Flowing

    Lava Flowing

    Lava flows like these Hawaii’an ones are endlessly mesmerizing. This type of flow is gravity-driven; rather than being pushed by explosive pressure, the lava flows under its own weight and that of the lava upstream. In fact, fluid dynamicists refer to this kind of flow as a gravity current, a term also applied to avalanches, turbidity currents, and cold drafts that sneak under your door in the wintertime. How quickly these viscous flows spread depends on factors like the density and viscosity of the lava and on the volume of lava being released at the vent. As the lava cools, its viscosity increases rapidly, and an outer crust can solidify while molten lava continues to flow beneath. Be sure to check out the full video below for even more gorgeous views of lava.  (Image/video credit: J. Tarsen, source; via J. Hertzberg)

  • Pyroclastic Flow

    Pyroclastic Flow

    Major volcanic eruptions can be accompanied by pyroclastic flows, a mixture of rock and hot gases capable of burying entire cities, as happened in Pompeii when Mt. Vesuvius erupted in 79 C.E. For even larger eruptions, such as the one at Peach Spring Caldera some 18.8 million years ago, the pyroclastic flow can be powerful enough to move half-meter-sized blocks of rock more than 150 km from the epicenter. Through observations of these deposits, experiments like the one above, and modeling, researchers were able to deduce that the Peach Spring pyroclastic flow must have been quite dense and flowed at speeds between 5 – 20 m/s for 2.5 – 10 hours! Dense, relatively slow-moving pyroclastic flows can pick up large rocks (simulated in the experiment with large metal beads) both through shear and because their speed generates low pressure that lifts the rocks so that they get swept along by the current. (Image credit: O. Roche et al., source)

  • Io’s Magma Ocean

    Io’s Magma Ocean

    Jupiter’s moon Io is the most volcanically active world in our solar system. The energy that drives its geological activity comes from tidal forces the moon experiences from Jupiter and from other Jovian moons. These forces flex the moon and heat its interior via friction. Previous models of Io’s tidal heating assumed a solid body, but their results predicted volcanoes in locations that did not match observations of the moon. A new study suggests that the missing piece of the puzzle is a subsurface ocean of magma. Highly viscous liquids like magma also generate heat when deformed by tidal forces, and applying this model to Io allowed scientists to better match the volcano distribution actually seen on the world. For more, check out NASA’s article. (Image credit: NASA; via Gizmodo; submitted by jshoer)

  • Featured Video Play Icon

    Calbuco

    Filmmaker Martin Heck captured incredible timelapse footage of the Chilean volcano Calbuco erupting earlier this year. Fluid dynamics on these enormous geophysical scales is always awe-inducing. In the beginning, clouds bob gently and flow around the landscape. Then the volcano erupts, and the towering ash cloud of the eruption roils with turbulence, displaying eddies with length scales from hundreds of meters down to centimeters. And when the hot ash has risen and cooled, it forms a cap that spreads horizontally. Nature is a wonderful demonstrator of fluid dynamics, but what always amazes me is how very alike flows are whether they are confined to a laboratory or take up an entire planet. (Video credit: M. Heck; via It’s Okay To Be Smart)

  • Featured Video Play Icon

    Bardarbunga Eruption

    I thought I was done with volcanoes for this week, but DJI’s aerial footage from Iceland’s Bardarbunga eruption is too fantastic not to share. The eruption is over a month old now and more than 25,000 earthquakes have been registered in Iceland since this eruption began. The lava field covers more than 46 square kilometers, and experts remain unsure how long the eruption will continue. The lava itself is a basalt, which is lower in viscosity than more silica-rich lava. This lower viscosity means that the gases dissolved in the rising magma can escape more easily, like carbon dioxide fizzing out of a soda. If the lava’s viscosity were higher, those dissolved gases would generate a more explosive eruption as they try to escape. (Video credit: DJI; via Wired)

  • Krakatoa

    Krakatoa

    Volcanoes seem to be a common topic these days. Yesterday Nautilus published a great piece by Aatish Bhatia on the 1883 eruption of Krakatoa, which tore the island apart and unleashed a sound so loud it was heard more than 4800 km away:

    The British ship Norham Castle was 40 miles from Krakatoa at the time of the explosion. The ship’s captain wrote in his log, “So violent are the explosions that the ear-drums of over half my crew have been shattered. My last thoughts are with my dear wife. I am convinced that the Day of Judgement has come.“

    In general, sounds are caused not by the end of the world but by fluctuations in air pressure. A barometer at the Batavia gasworks (100 miles away from Krakatoa) registered the ensuing spike in pressure at over 2.5 inches of mercury. That converts to over 172 decibels of sound pressure, an unimaginably loud noise. To put that in context, if you were operating a jackhammer you’d be subject to about 100 decibels. The human threshold for pain is near 130 decibels, and if you had the misfortune of standing next to a jet engine, you’d experience a 150 decibel sound. (A 10 decibel increase is perceived by people as sounding roughly twice as loud.) The Krakatoa explosion registered 172 decibels at 100 miles from the source. This is so astonishingly loud, that it’s inching up against the limits of what we mean by “sound.” #

    Those are some mindbogglingly enormous numbers. Aatish does a wonderful job of explaining the science behind an explosion whose effects ricocheted through the atmosphere for days afterward. Check out the full article over at Nautilus.  (Image credit: Parker & Coward, via Wikipedia)

  • Pyroclastic Flow

    Pyroclastic Flow

    Saturday morning Japan’s Mount Ontake erupted unexpectedly, sending a pyroclastic flow streaming down the mountain. Many, though sadly not all, of the volcano’s hikers and visitors survived the eruption. Pyroclastic flows are fast-moving turbulent and often super-heated clouds filled with ash and poisonous gases. They can reach speeds of 700 kph and temperatures of 1000 degrees C. The usual gases released in a pyroclastic flow are denser than air, causing the cloud to remain near the ground. This is problematic for those trying to escape because the poisonous gases can fill the same low-lying areas in which survivors shelter. Heavy ashfall from the flow can destroy buildings or cause mudslides, and the fine volcanic glass particles in the ash are dangerous to inhale. The sheer power and scale of these geophysical flows is stunning to behold. Those who have witnessed it firsthand and survived are incredibly fortunate. For more on the science and history of Mount Ontake, see this detailed write-up at io9. (Image credits: A. Shimbun, source video; K. Terutoshi, source video; via io9)

  • Volcanic Vortex

    Volcanic Vortex

    This infrared image shows a kilometer-high volcanic vortex swirling over the Bardarbunga eruption. The bright red at the bottom is lava escaping the fissure, whereas the yellow and white regions show rising hot gases. Although the vortex looks similar to a tornado, it is actually more like a dust devil or a so-called fire tornado. All three of these vortices are driven by a heat source near the ground that generates buoyant updrafts of air. As the hot gases rise, cooler air flows in to replace them. Any small vorticity in that ambient air gets amplified as it’s drawn to the center, the same way an ice skater spins faster when she pulls her arms in. With the right conditions, a vortex can form. Unlike a harmless dust devil, though, this vortex is likely filled with sulphur dioxide and volcanic ash and would pose a serious hazard to aviation.  (Image credit: Nicarnica Aviation; source video; via io9)

  • Lava Physics

    Lava Physics

    Lava is rather fascinating as a fluid. Lava flow regimes range from extremely viscous creeping flows all the way to moderately turbulent channel flow. Lava itself also has a widely varying rheology, with its bulk properties like viscosity and its response to deformation changing strongly with temperature and composition. As lava cools, instabilities form in the fluid, causing the folding, coiling, branching, swirling, and fracturing associated with different types and classes of lava. (Image credit: E. Guddman, via Mirror)

  • Volcanic Vortices from Etna

    Volcanic Vortices from Etna

    Italy’s Mount Etna is erupting again, producing a series of beautiful vortex rings. Like a dolphin’s bubble ring or a vortex cannon, the volcano’s rings are formed when gases are rapidly expelled through a narrow opening. Such formations are extremely common but are generally not visible to the eye. In this case, steam has gotten entrained into the rings to make them visible. Vortex rings can maintain their structure over substantial distances. The photographer of these rings noted that they lasted as many as ten minutes before dissipating. (Photo credit: T. Pfeiffer; via NatGeo)