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  • richardmitnick 1:12 pm on October 25, 2018 Permalink | Reply
    Tags: , , , , , Undersea volcanoes   

    From EarthSky: “Eruption of the world’s deepest undersea volcano” 

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    From EarthSky

    October 25, 2018
    Eleanor Imster

    A research team has documented a volcanic eruption in the western Pacific Ocean that’s deeper below the ocean surface than Mount Rainier’s height above sea level.

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    Researchers used remotely operated vehicles to explore the deep waters of the Mariana Trench. Image via Oregon State University.

    A team of researchers has documented a recent volcanic eruption in the western Pacific Ocean about 2.8 miles (4.5 km) below the ocean surface that they describe as the deepest known eruption on Earth – deeper below the ocean surface than Mount Rainier’s height above sea level.

    The researchers say the eruption probably happened between 2013-2015 on the Mariana back-arc, a zone of the sea floor with active volcanoes in the Pacific Ocean’s Mariana Trench. The Mariana Trench is the deepest part of the earth’s oceans, and the deepest location of the earth itself. It’s located just east of the 14 Mariana Islands near Japan. It was created by ocean-to-ocean subduction, a phenomenon in which a tectonic plate topped by oceanic crust is subducted beneath another plate also topped by oceanic crust.

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    Location of the Mariana Trench. Image via Wikipedia.

    Bill Chadwick is a marine geologist at Oregon State University and lead author on the study, published October 23, 2018 in the peer-reviewed journal Frontiers in Earth Science. Chadwick said in a statement:

    “We know that most of the world’s volcanic activity actually takes place in the ocean, but most of it goes undetected and unseen. That is because undersea quakes associated with volcanism are usually small, and most of the instrumentation is far away on land.

    Many of these areas are deep and don’t leave any clues on the surface. That makes submarine eruptions very elusive.”

    The Mariana back-arc eruption was first discovered in December 2015 by cameras aboard an autonomous underwater vehicle. Photos revealed the presence of a pristine dark, glassy lava flow on the seafloor with no sediment cover. Venting of milky hydrothermal vent fluid indicated that the lava flow was still warm, and therefore very young.

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    Fresh lava from the sea floor. Image via Oregon State University.

    Data indicated that there had been major depth changes in the area between surveys in 2013 and 2015, the researchers said, which is consistent with an eruption. The new lava flows stretched over an area about 4.5 miles (7.2 km) long and ranged in thickness between 130-450 feet (40-137 meters).

    The scientists returned in April and December of 2016 and used two remotely operated vehicles to explore the site. The new observations showed a rapidly declining hydrothermal system on the lava flows, suggesting the eruption had taken place only months before its discovery the previous year. Chadwick said:

    “Typically after an eruption, there is heat released and venting for a few years and organisms will colonize the vents, creating a new ecosystem. But after a while, the system cools down and the mobile organisms will leave. There was still some venting, but it had obviously greatly declined.”

    Bottom line: An undersea volcanic eruption discovered in the Pacific Ocean’s Mariana Trench is the deepest known.

    Source: A Recent Volcanic Eruption Discovered on the Central Mariana Back-Arc Spreading Center

    See the full article here .


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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 12:57 pm on December 13, 2017 Permalink | Reply
    Tags: , , Hunga Tonga vulcanic island, Landsat 8 (NASA), Nobody knows for sure how long this volcanic island will stand, , Undersea volcanoes,   

    From Science Alert: “This Pacific Island Appeared Only 3 Years Ago, And Could Be Doomed Already” 

    ScienceAlert

    Science Alert

    13 DEC 2017
    PETER DOCKRILL

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    (Pleiades-1A ©2015 CNES Distribution Airbus DS)

    Born in a fire in the ocean.

    Three years ago, the place you’re reading about now did not exist.

    Then, suddenly, an underwater volcano erupted in the middle of the South Pacific, and by the time the smoke and ash cleared, a new land mass stood revealed – an island that no-one had ever seen before.

    That’s how the volcanic island of Hunga Tonga-Hunga Ha’apai (Hunga Tonga) came into the world in January 2015, nestling in between two existing, uninhabited Polynesian islands that make up part of the Kingdom of Tonga.

    In the last 150 years, only three volcanic islands have emerged like this and survived for more than a few months, with the most famous of them being Surtsey – which appeared off the southern coast of Iceland during a four-year eruption that began in 1963.

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    (NASA/Damien Grouille/Cecile Sabau)

    Scientists have studied Surtsey for decades, but Hunga Tonga – informally named after the submarine volcano above which it sits – is set apart by being the only kind of island like this to emerge in the era of the modern satellite, which gives us a whole new way of studying how these rocky land masses evolve.

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    Hunga Tonga-Hunga Haʻapai island in January 2017. Landsat 8 (NASA).

    For example, just for fun, if you do a search for ‘Hunga Tonga‘ in Google Maps’ regular Maps view, you’ll see an outdated illustration of two islands separated by an expanse of blue water.

    But if you flick the switch to Satellite view, the newly born island is revealed in all its glory.

    That kind of perspective is what intrigues scientists, who are using satellite data to learn what they can about such volcanic upstarts, before erosion inevitably sees Hunga Tonga vanish away again under the waves.

    “There’s a huge amount of material that came out from this eruption, possibly larger than at Surtsey,” says geologist Vicki Ferrini from Columbia University, who is studying the island with researchers from NASA.

    “The other interesting thing is that the two islands that surround this new land mass have some pretty tough substrate, so there’s something happening to help make this solidify and stay in place, chemically.”

    Initially, scientists estimated Hunga Tonga might only last for a few months before disappearing, but researchers now think the island – which covers some 200 hectares (nearly 500 acres) and extends as high as 120 metres (400 feet) above the ocean – could survive for as long as 30 years.

    Using satellite data updated in real time, the team is developing 3D maps of the island’s topography, studying its shifting coastlines and the amount of its land that sits above sea level.

    “Our interest is to calculate how much the 3D landscape changes over time, particularly its volume,” says the chief scientist of NASA’s Goddard Space Flight Centre, Jim Garvin, who spent his formative years studying Surtsey.

    “It’s the first step to understand erosion rates and processes and to decipher why it has persisted longer than most people expected.”

    The insights gleaned won’t just tell us things about how pop-up islands sitting in the South Pacific bide their time. It could also inform us about the behaviour of volcanic land forms that exist much, much farther away.

    “Everything we learn about what we see on Mars is based on the experience of interpreting Earth phenomena,” says Garvin.

    “We think there were eruptions on Mars at a time when there were areas of persistent surface water. We may be able to use this new Tongan island and its evolution as a way of testing whether any of those represented an oceanic environment or ephemeral lake environment.”

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    (©2017 DigitalGlobe)

    It’s a somewhat fantastic premise, but NASA thinks Honga Tonga’s unique geography could provide a new model for investigations into the history of water on Mars, which could help us understand if life ever existed – or yet does – on the Red Planet.

    But time is short.

    Nobody knows for sure how long this volcanic island will stand, but similarly, nobody thinks it will be forever, with Honga Tonga’s unstable cliffs of solidified ash expected to erode entirely in the years ahead.

    So the impetus is on scientists to learn what they can from the ‘baby island’ before the waves claim it once more.

    “This island is fighting for its life,” Garvin told the media this week.

    “And our predictions suggest we’ve got potentially another decade [or more] to watch this thing evolve from space.”

    The findings were presented at the 2017 Fall Meeting of the American Geophysical Union in New Orleans this week.

    See the full article here .

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  • richardmitnick 12:34 pm on May 25, 2017 Permalink | Reply
    Tags: , , Plate attenuation, , Undersea volcanoes   

    From UCSB: “The Birth and Death of a Tectonic Plate” 

    UC Santa Barbara Name bloc
    UC Santa Barbara

    May 24, 2017
    Julie Cohen

    Geophysicist Zachary Eilon developed a new technique to investigate the underwater volcanoes that produce Earth’s tectonic plates

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    Attenuation values recorded at ocean-bottom stations. Radial spokes show individual arrivals at their incoming azimuth; central circles show averages at each station

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    Geophysicist Zachary Eilon. Photo Credit: COURTESY IMAGE

    Several hundred miles off the Pacific Northwest coast, a small tectonic plate called the Juan de Fuca is slowly sliding under the North American continent. This subduction has created a collision zone with the potential to generate huge earthquakes and accompanying tsunamis, which happen when faulted rock abruptly shoves the ocean out of its way.

    In fact, this region represents the single greatest geophysical hazard to the continental United States; quakes centered here could register as hundreds of times more damaging than even a big temblor on the San Andreas Fault. Not surprisingly, scientists are interested in understanding as much as they can about the Juan de Fuca Plate.

    This microplate is “born” just 300 miles off the coast, at a long range of underwater volcanoes that produce new crust from melt generated deep below. Part of the global mid-ocean ridge system that encircles the planet, these regions generate 70 percent of the Earth’s tectonic plates. However, because the chains of volcanoes lie more than a mile beneath the sea surface, scientists know surprisingly little about them.

    UC Santa Barbara geophysicist Zachary Eilon and his co-author Geoff Abers at Cornell University have conducted new research — using a novel measurement technique — that has revealed a strong signal of seismic attenuation or energy loss at the mid-ocean ridge where the Juan de Fuca Plate is created. The researchers’ attenuation data imply that molten rock here is found even deeper within the Earth than scientists had previously thought. This in turn helps scientists understand the processes by which Earth’s tectonic plates are built, as well as the deep plumbing of volcanic systems. The results of the work appear in the journal Science Advances.

    “We’ve never had the ability to measure attenuation this way at a mid-ocean ridge before, and the magnitude of the signal tells us that it can’t be explained by shallow structure,” said Eilon, an assistant professor in UCSB’s Department of Earth Science. “Whatever is down there causing all this seismic energy to be lost extends really deep, at least 200 kilometers beneath the surface. That’s unexpected, because we think of the processes that give rise to this — particularly the effect of melting beneath the surface — as being shallow, confined to 60 km or less.”

    According to Eilon’s calculations, the narrow strip underneath the mid-ocean ridge, where hot rock wells up to generate the Juan de Fuca Plate, has very high attenuation. In fact, its levels are as high as scientists have seen anywhere on the planet. His findings also suggest that the plate is cooling faster than expected, which affects the friction at the collision zone and the resulting size of any potential megaquake.

    Seismic waves begin at an earthquake and radiate away from it. As they disperse, they lose energy. Some of that loss is simply due to spreading out, but another parameter also affects energy loss. Called the quality factor, it essentially describes how squishy the Earth is, Eilon said. He used the analogy of a bell to explain how the quality factor works.

    “If I were to give you a well-made bell and you were to strike it once, it would ring for a long time,” he explained. “That’s because very little of the energy is actually being lost with each oscillation as the bell rings. That’s very low attenuation, very high quality. But if I give you a poorly made bell and you strike it once, the oscillations will die out very quickly. That’s high attenuation, low quality.”

    Eilon looked at the way different frequencies of seismic waves attenuated at different rates. “We looked not only at how much energy is lost but also at the different amounts by which various frequencies are delayed,” he explained. “This new, more robust way of measuring attenuation is a breakthrough that can be applied in other systems around the world.

    “Attenuation is a very hard thing to measure, which is why a lot of people ignore it,” Eilon added. “But it gives us a huge amount of new information about the Earth’s interior that we wouldn’t have otherwise.”

    Next year, Eilon will be part of an international effort to instrument large unexplored swaths of the Pacific with ocean bottom seismometers. Once that data has been collected, he will apply the techniques he developed on the Juan de Fuca in the hope of learning more about what lies beneath the seafloor in the old oceans, where mysterious undulations in the Earth’s gravity field have been measured.

    “These new ocean bottom data, which are really coming out of technological advances in the instrumentation community, will give us new abilities to see through the ocean floor,” Eilon said. “This is huge because 70 percent of the Earth’s surface is covered by water and we’ve largely been blind to it — until now.

    “The Pacific Northwest project was an incredibly ambitious community experiment,” he said. “Just imagine the sort of things we’ll find out once we start to put these instruments in other places.”

    See the full article here .

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    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 9:05 am on January 20, 2016 Permalink | Reply
    Tags: , , Undersea volcanoes   

    From The Seattle Times: “UW scientists capture underwater eruption with new fiber-optic array, set up HD web cam” 

    Seattle Times bloc

    The Seattle Times

    January 17, 2016
    Sandi Doughton

    The idea was hatched in a bar more than two decades ago.

    University of Washington oceanographer John Delaney and a colleague were nursing cocktails and venting their frustration with the traditional approach to studying the underwater world.

    The ocean and seafloor are dynamic environments, with tectonic plates pulling apart, superhot fluids gushing from hydrothermal vents and an ever-shifting cast of creatures on the move.

    Techtonic plates
    The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which float on the fluid-like (visco-elastic solid) asthenosphere. The relative fluidity of the asthenosphere allows the tectonic plates to undergo motion in different directions. This map shows 15 of the largest plates. Note that the Indo-Australian Plate may be breaking apart into the Indian and Australian plates, which are shown separately on this map.

    But scientists could only catch glimpses of what was going on under the surface during brief, costly research cruises.

    Temp 1
    In its first success, a new system of cabled instruments allowed scientists to “watch” an underwater volcano erupt. Axial Seamount sits 300 miles off the NW coast under a mile of water. New lava flows, shown in orange, were up to 417 feet thick.

    When his friend mentioned a new technology called fiber optics, it fired Delaney’s imagination. He grabbed a napkin and sketched out a network of sensors attached to cables that could transmit data instantly and continuously. He called it an underwater observatory.

    After 25 years of pitching the idea to anyone who would listen and scrounging for money, Delaney is finally seeing that vision realized. And the scientific payoffs started with a bang that even he couldn’t have anticipated.

    With the completion this month of a data portal, information and images from a suite of 140 instruments off the Northwest coast are finally flowing to scientists around the world. Even before the data were widely disseminated, the observatory allowed researchers to track, for the first time, the eruption of an underwater volcano as it happened.

    “That was incredibly exciting,” Delaney said. “This signals a new era in ocean science, where the cable allows us to actually be there 24/7, 365 days a year.”

    Temp 2
    Hot, microbe-rich fluids flow out of a caldron in a seafloor lava flow. Scientists say microbes associated with underwater eruptions might shed light on the origins of life. (University of Washington / Ocean Observatories Initiative)

    Temp 3
    A cabled, high-definition camera on the seafloor near Axial Seamount streams live images of a 13-foot-tall black smoker thermal chimney,being called the Mushroom, which is covered with tube worms, palm worms and limpets. (University of Washington / Ocean Observatories Initiative)

    Eruption under way

    The eruption provided a serendipitous showcase for the observatory’s power to capture events that scientists had previously been able to examine only after the fact.

    In April 2015, just months after a team from the UW and other institutions installed the final instruments on the $200 million cabled network and powered it up, the new seismometers detected an uptick in rumblings under a submarine volcano called Axial Seamount. Located 300 miles off the Oregon coast and covered by nearly a mile of water, the sprawling volcano straddles a ridge where the seafloor splits and new crust is born as molten rock rises from the depths.

    Scientists were glued to their computer terminals, watching the shaking build to a crescendo. In one 24-hour-period, the instruments recorded more than 8,000 small quakes as magma muscled its way upward.

    Then the earthquakes dropped off abruptly, as if someone had thrown a switch. At the same time, pressure sensors revealed that the seamount — which had been swelling for several years — deflated like a balloon.

    That’s exactly what you would expect to see from a volcano that just ejected massive amounts of lava — but scientists weren’t sure at first where the molten rock had gone.

    Then they looked more closely at the seismic data and saw bursts of small earthquakes from an unexpected location on the volcano’s northern flank. Hydrophones also picked up the sound of explosions in the area, probably generated when pressurized gas burst from the lava, said UW marine geophysicist William Wilcock.

    A few months later, when a research crew visited the site by ship, Wilcock and his colleagues relied on the observations from the cabled observatory to tell them exactly where to look for freshly erupted rock.

    “It was pretty neat,” Wilcock said. “They went there and found this very thick lava flow.”

    A remotely operated vehicle lowered from the ship recorded stunning video of formations called pillow basalts, created as magma erupts into water, said UW oceanographer Deborah Kelley, chief scientist for the expedition. In places, the new lava was more than 40 stories thick.

    Hot fluid still gushed from openings in the new seafloor. Vents called snowblowers spewed blizzards of white minerals encrusted with microbes. Mats of microscopic organisms were already beginning to colonize the newly erupted basalt.

    And none of the instruments were damaged.

    “We were phenomenally lucky,” Kelley said. “We got a nice eruption and it didn’t take out our array.”

    Now that all the data are available, Kelley is eager to see whether the eruption generated a “megaplume” of superheated water and chemicals similar to the ash clouds that rise from volcanoes on land.

    In addition to seismometers and pressure gauges, the observatory includes instruments that measure ground tilt, water temperature, oxygen levels and chemical composition. Other sensors can collect microbes and analyze their DNA. A few instruments were designed to zip up and down on vertical cables, collecting samples at different depths.

    Kelley also hopes to explore the links between underwater earthquakes and eruptions and the microbes that thrive in the harsh environment — and may represent the origins of life on Earth and models for possible life on other planets.

    “The idea is that this array will be in place for at least 25 years,” she said. “There are so many questions we can address.”

    Dream come true

    Live video from a high-definition camera on the seafloor is also streaming online now. It’s not continuous yet, but Delaney couldn’t wait to share it with his students.

    “I’ve been dreaming about that for more than 20 years,” he said in his office last week, as he gazed at an image of a 13-foot-tall hydrothermal vent called a black smoker, with scalding water flowing from its top and a thick blanket of palm worms, filamentous bacteria and limpets clinging to its sides.

    “What you’re looking at is what’s happening on the bottom of the ocean, 400 kilometers away — right this second,” he said, shaking his head as if he couldn’t quite believe it himself.

    When Delaney proposed the underwater observatory, many scientists dismissed it as impossibly ambitious — and impossible to pull off. Others worried it would gobble up too much of the slim budget allotted to oceanographic research.

    Colleagues use the word “visionary” to describe Delaney’s view of the future of oceanography and his passion for the observatory project. But it also took a lot of time shuttling back and forth between Seattle and Washington, D.C., along with nitty-gritty negotiation to build support, secure funding and orchestrate the installation, said marine geologist Daniel Fornari, of Woods Hole Oceanographic Institution.

    “John is a very determined man,” Fornari said. “He lived and breathed this for two decades.”

    Delaney is also eloquent in describing humanity’s connection to and reliance on the oceans, said marine scientist Maya Tolstoy, of Lamont-Doherty Earth Observatory at Columbia University. A section of Delaney’s website is devoted to Pablo Neruda and other poets who explore the mysteries of the sea and human soul.

    “I would describe John as the poet laureate of the seafloor,” Tolstoy said.

    After multiple delays and reductions in scope, the National Science Foundation funded the array as part of its broader Ocean Observatories Initiative.

    The fiber-optic infrastructure and the scientific instruments were all in place by the end of 2014. But scientists around the world were forced to wait more than a year for completion of the data portal.

    The bugs that remain in the data-delivery system aren’t enough to dim Delaney’s exhilaration at seeing the observatory begin to function as it was meant to.

    And at the age of 74, he’s already looking ahead.

    The existing instruments are too far offshore to closely monitor the submarine fault called the Cascadia Subduction Zone, which can unleash monster earthquakes and tsunamis. So Delaney is pushing to add a dedicated network of seismometers and pressure gauges.

    He’s also enthusiastic about new, autonomous gliders and other mobile platforms capable of performing experiments and exploring the expanses between fixed instruments.

    “We’re still at the very early stage with the cable,” he said. “We’re planting the seeds for the next generation of oceanography.”

    See the full article here .

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