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  • richardmitnick 4:00 pm on February 27, 2019 Permalink | Reply
    Tags: , , , , , Stromboli volcano,   

    From Stanford University: “Volcanoes, archaeology and the secrets of Roman concrete” 

    Stanford University Name
    From Stanford University

    February 26, 2019
    Josie Garthwaite

    Geophysical processes have shaped Pozzuoli, Italy, like few other places in the world. Stanford students applied modern tools to understand those links and what it means to live with natural hazards as both threat and inspiration.

    1
    Students gather atop Mount Vesuvius in southern Italy and listen as geophysicist Tiziana Vanorio discusses how volcanic activity has shaped the surrounding region. (Image credit: Kurt Hickman)

    High above Italy’s Tyrrhenian Sea, off the north coast of Sicily, 13 students sit atop Stromboli Volcano as it erupts. Ash falls on their shoulders and ping-ping-pings their helmets. The ground beneath their feet trembles.

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    The Island of Stromboli, Shot 2004 Sep 28 by Steven W. Dengler.

    “It’s one thing to read and talk about seismic and volcanic hazard; it’s another thing to experience it,” said geophysicist Tiziana Vanorio, an assistant professor in Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “I wanted to share this with them.”

    The journey to Stromboli had begun the day before in Vanorio’s hometown, Pozzuoli, a colorful port city founded by the Greeks and later occupied by the Romans, at the center of a volcanic caldera, or depression, known as Campi Flegrei. Vanorio, the 13 students and two teaching associates boarded a hydrofoil in Naples and sailed south across the deep blue water of the Tyrrhenian for nearly four quiet hours before catching sight of smoke, steam and gases puffing from Stromboli’s cone.

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    During their two-week trip, students visited two volcanoes in Italy and local towns shaped by their proximity. (Image credit: Yvonne Tang)

    Reaching the top would prove more arduous – a five-hour climb up steep slopes of ash and rock. Sedimentologist Nora Nieminski, a postdoctoral researcher at Stanford Earth and a guest instructor on the trip, sprinted ahead to shoot drone footage that she would later help the students manipulate to create 3D models of the volcano. But the rest of the group walked without hurry. Halfway to the top, they stopped to rest near a dark scar on the volcano’s northern flank known as the Sciara del Fuoco, where the volcano has collapsed on itself.

    Dionne Thomas, ’20, a student on the trip who is majoring in chemical engineering, remembers smelling dirt and ash, seeing the Tyrrhenian Sea reflecting the sky’s late-afternoon wash of orange and blue, and counting down the minutes between small bursts of lava from a caldera upslope. While she noticed the weight of exhaustion from the long climb, she said, “I felt really strong.”

    Thomas and the 12 other students on the trip visited Stromboli as part of a three-week seminar in southern Italy focused on volcanoes, archaeology and the science of Roman concrete – an exceptionally durable material that may hold insights for future materials that are more sustainable or even suitable for building habitats on Mars.

    Offered through Stanford’s Bing Overseas Studies Program, the seminar is an opportunity to draw visceral connections between science and history, and to gain a better understanding of Earth along the way.

    Nature’s laboratory

    The Neapolitan Province in southern Italy is an ideal place to dive into the science of natural hazards and how they have played into daily life and innovation over thousands of years. Densely populated and peppered with dozens of volcanoes, the region ranks as one of the most hazardous on Earth. The ruins of a Roman harbor and an emperor’s villa can be found offshore, sunken like Atlantis as a result of unrest in Earth’s crust. “Not many places on Earth experience this kind of seismicity and volcanism, while being an ancient town and functioning as a modern society,” Vanorio said. “That’s the beauty of the place.”

    Underlying the seminar’s excursions and daily lessons in geophysics, the properties of Roman concrete and 3D modeling from drone images was a larger exercise in finding connections between different fields of study. It’s no accident that students chosen to participate in the seminar represented a wide range of majors, including computer science, physics, classics, chemical engineering and political science.

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    The ancient Italian city of Pozzuoli was shaped by volcanic activity. (Image credit: Kurt Hickman)

    “There are still scientific questions that we don’t know how to answer,” said Vanorio, who discovered natural processes deep in the subsurface of Campi Flegrei that mirror those in Roman concrete, and has used historical texts to shed light on strengths and the characteristics of both volcanic and engineered materials. “The more we leverage knowledge across different disciplines, the more we can address and solve those problems.”

    For Amara McCune, BS ’18, who joined a previous seminar in the region led by Vanorio in 2016, the intermingling of geophysics with dives into the region’s culture proved a powerful mix. “The unique combination of learning about Pompeii, volcanic uplift and Rome while being on-site, hearing from local guides and having archaeological and geological experts point out features of a location made for an incredibly rich learning experience,” she said.

    ______________________________________________________________________
    Materials inspired by nature
    4
    Romans used concrete made with volcanic ash to build long-lasting structures like the amphitheater in Pozzuoli, Italy. (Image credit: Nora Nieminski)

    Nearly all concrete today is based on a recipe developed in the early 1800s, which requires a process that’s heavily carbon-intensive. But ancient Romans invented a different recipe for concrete structures that have survived for millennia. Research now suggests this ancient material and the volcanoes that made its key components may hold clues for more sustainable building materials.
    ______________________________________________________________________

    Now pursuing a PhD in physics, McCune said the seminar in southern Italy helped to broaden her thinking about how she might apply her degree. “It made me more open to different fields and eager to learn the history and intricacies of the natural world around us,” she said.

    During the most recent trip, darkness fell as the group, giddy in anticipation of the volcano’s powerful eruptions, settled in around Stromboli’s rim. “It explodes violently and without warning – these big, loud bang explosions followed by incandescent ash flying into the air,” explained Dulcie Head, a teaching assistant on the trip and a PhD student in geophysics.

    By this time, the students could see the ash swirling around them as more than volcanic dirt. They knew that similar ash had been a key ingredient in construction of the amphitheater, harbor and ancient marketplace in Pozzuoli, and even the Pantheon in Rome, with its massive, unreinforced dome – the largest in the ancient world.

    “Pozzuoli is possibly the place where Romans, by looking at nature, were inspired to make an iconic material,” Vanorio said. They developed a recipe for concrete that lasts for thousands of years using volcanic ash, lime, tiny volcanic rocks and water, while modern concrete often crumbles within 50 years.

    Atop Stromboli, which scientists carefully monitor for safety, the students also had enough Earth science churning through their heads to see the volcano itself as a natural laboratory. “This volcano is literally producing new rocks as we’re sitting here. It’s throwing them at us,” Head explained. “It’s exciting to see such an active process, where a natural event also produces new materials.”

    The group bounced and slid down a path on the volcano’s slopes wearing gas masks to protect their lungs from ash and sand kicked up by their feet. Back at their hotel at the foot of the island, they peeled off their masks and washed away Stromboli’s detritus. Later, the group learned how to calculate the trajectory and velocity of the volcano’s arcing ash projectiles with particle-tracking software.

    “This was one way for us to use time-lapse images,” Vanorio said. “I wanted students from Earth science, from the classics, and engineers to learn how to use this tool because we are finding ourselves using these kinds of images more and more – often captured by drone – whether it’s to analyze inaccessible outcrops of rocks or map vast ancient sites or a building.”

    What could have seemed like abstract calculations took on greater resonance in light of the group’s up-close encounter with the eruption. “I’ll never forget the bright sparks of the eruption against the dark night,” said Sylvia Choo, ’20, who is majoring in classics and biology. “It was incredible to experience the great force of nature.”

    Ancient city

    Some 150 miles across the cool Tyrrhenian, within the Campi Flegrei or “Burning Fields” caldera, lies downtown Pozzuoli. In this city best known to many Italians as the birthplace of Sophia Loren, the ruins of a Roman marketplace are a hub for cross-disciplinary connections.

    Pozzuoli sits on a restless, Manhattan-sized swath of coast where the rotten-egg smell of sulfur laces the air. Solfatara crater, home of Vulcan, the Roman god of fire, gurgles on the edge of town. And just offshore, sculptures, thermal baths, a villa, bright tiled mosaics and other archaeological ruins rest more than 30 feet below sea level, victims of the caldera’s subsidence.

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    Parts of Pozzuoli’s ancient architecture contain records of long-term subsidence and brief periods of uplift. Rapid uplift during the 1980s left the town’s harbor too shallow for docking. (Image credit: Kurt Hickman)

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    Students swam through a sunken Roman resort town in the underwater archaeological park of Baiae off the coast of Pozzuoli. (Image credit: Kurt Hickman)

    Near Pozzuoli’s modern-day waterfront, three columns stand amid the ruins of the old marketplace, or Macellum. The students knew from their studies on campus in the spring that the marble trio held a 2000-year record of long-term subsidence and brief periods of uplift. So as the columns came into view when the group first walked down from their villa residence, several students exclaimed, “Oh, there they are!”

    Gathering close to the columns for a lecture from Vanorio while Nieminski’s drone buzzed overhead, they could see bands of tiny holes bored by so-called “stone-eater” mussels – marine mollusks that drilled up and down the columns as the rise and fall of the caldera changed how much of the structures extended above the waterline. “They literally made a mark on history,” Choo said.

    Using skills developed in on-campus seminars led by Nieminski, the students were able to analyze history at the Macellum and other sites with a lighter touch. They built 3D models of the marketplace from Nieminski’s drone imagery and manipulated them with software to take measurements and answer scientific questions of their own devising.

    Thomas, for example, examined the different materials in the columns to understand how weathering and water pressure from below played out over time. The project, she said, allowed her to weave together knowledge from chemical engineering, physics and math, as well as the geophysics lessons from the seminar. “After this seminar, I am even more convinced that many fields can overlap,” she said.

    Restless Earth

    Ups and downs are part of the fabric of life in Pozzuoli. In the early 1980s, the ground rose more than 6 feet in just two years, an alarming rate of uplift that reshaped the town, leaving the harbor too shallow for docking and forcing the relocation of schools and shops.

    The rising seabed also triggered enough earthquakes to prompt evacuation of nearly 40,000 people – including Vanorio, then a teenager – for two years beginning in 1982. “Everyone was worried,” she said. “People were expecting an eruption, and we were really concerned about the seismic hazard. The houses were not retrofitted seismically.”

    But as seminar students learned through lectures and readings this summer, the episode tipped off Stanford scientists to an unusual toughness in the rock here. Other volcanic calderas, like Yellowstone or the Long Valley, located east of Yosemite National Park, tend to release the energy accumulated from uplift fairly soon through earthquakes. “Those calderas experience uplift and then almost immediately, seismic activity starts,” Vanorio explained. “The rocks deform and then they fracture.”

    In Pozzuoli, earthquakes didn’t begin until the Campi Flegrei caldera had deformed by nearly 3 feet. “The question from a rock physics point of view has been, what kind of rocks in the subsurface are able to accommodate such large strain without immediately cracking?” The rock capping this caldera, it turns out, contains fibrous minerals mirroring those in Roman concrete that allow it to stretch and bend before failing under stress.

    At the marketplace, Vanorio also pointed out that the durability of Roman concrete can be seen in sections of the ancient walls where the bricks made of tuff – a kind of volcanic rock – eroded away long ago, but the mortar made with volcanic ash and lime still remains. “At the end of the day, these ancient sites are made of Earth materials that degrade and change over time,” Vanorio said. “We can use rock physics to understand those materials and learn to preserve them better.”

    See the full article here .


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  • richardmitnick 12:27 pm on December 27, 2017 Permalink | Reply
    Tags: , , , , , , , Scientists Discover Stromboli-Like Eruption on Volcanic Moon, Stromboli volcano,   

    From Eos: “Scientists Discover Stromboli-Like Eruption on Volcanic Moon” 

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    12.27.17
    JoAnna Wendel

    1
    NASA’s New Horizons mission captured this composite image of an eruption on Jupiter’s moon Io while en route to Pluto in 2007. The erupting volcano is Tvashtar, in the northern hemisphere. New evidence suggests that Io can produce Stromboli-type eruptions, events never before observed on Io. The new data could help scientists figure out the makeup of Io’s interior. Credit: NASA/JPL/University of Arizona​

    NASA/New Horizons spacecraft

    Twenty years ago, “something huge, powerful, and energetic happened at the surface of Io,” said Ashley Davies, a volcanologist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Davies and his colleagues think they’ve discovered a type of eruption never before spotted on one of the most volcanically active bodies in the solar system.

    The researchers stumbled on the eruptive evidence in data from NASA’s Galileo orbiter mission, which explored the Jupiter system from 1995 to 2003. They think the data reflect a Strombolian eruption, a violent event named for Italy’s energetic Stromboli Volcano.

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    Stromboli, one of the world’s most active volcanoes, ejects large, hot volcanic bombs in this long-exposure image of the northeastern region of the summit crater terrace. During a May 2016 pilot project, the authors [Nicolas Turner, Bruce Houghton, Jacopo Taddeucci, Jost von der Lieth, Ullrich Kueppers, Damien Gaudin, Tullio Ricci, Karl Kim, and Piergiorgio Scalato 27 September 2017] sent unmanned aerial vehicles where humans couldn’t go to capture images and gather data on the locations and characteristics of Stromboli’s craters and vents. Credit: Rainer Albiez/Shutterstock.com

    But wait, you ask, didn’t Galileo plunge into Jupiter’s atmosphere at the end of its mission, way back in 2003?

    NASA/Galileo 1989-2003

    Well, yes. But the orbiter, at that point, had collected so much data about the Jovian system and its Galilean moons (Ganymede, Io, Callisto, and Europa) that scientists still haven’t waded through it all, even 14 years later.

    Davies presented the unpublished research on 13 December at the American Geophysical Union’s 2017 Fall Meeting in New Orleans, La.

    Serendipitous Data

    Io’s surface is constantly gushing lava—every million years or so, the entire moon’s surface completely regenerates. From towering lava fountains that can reach 400 kilometers high to violently bubbling lava lakes that burst through freshly cooled crust, these oozing lava fields can stretch many thousands of square kilometers.

    On this 3,600-kilometer-wide moon, eruptions take place “on a scale that simply isn’t seen on Earth today but was once common in Earth’s past,” Davies said. The scale, frequency, and intensity of Io’s eruptions make it a perfect analogue of early Earth, he continued, back when our blue planet was just a barren hellscape of lava.

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    A video of an Io eruption captured by New Horizons in 2007. Credit: NASA/Johns Hopkins University Applied Physics Laboratory

    Davies found evidence for the eruption he reported at Fall Meeting in data from Galileo’s Near Infrared Mapping Spectrometer (NIMS), which took pictures of the moon in the infrared wavelengths. This instrument allowed researchers to measure the thermal emissions, or heat, coming off the volcanically active moon.

    Stromboli Eruption

    While looking through the NIMS temperature data, Davies and his colleagues spotted a brief but intense moment of high temperatures that cooled oddly quickly. This signal showed up as a spike in heat from a region in the southern hemisphere called Marduk Fluctus. First, the researchers saw a heat signal jump to 4–10 times higher than background, or relatively normal, levels. Then just a minute later, the signal dropped about 20%. Another minute later, the signal dropped another 75%. Twenty-three minutes later, the signal had plummeted to the equivalent of the background levels.

    This signature resembled nothing Davies had seen before from Io. The lava flows and lava lakes are familiar: Their heat signals peter out slowly because as the surface of a lava flow cools, it creates a protective barrier of solid rock over a mushy, molten inside. Heat from magma underneath conducts through this newly formed crust and radiates from Io’s surface as it cools, which can take quite a long time.

    This new heat signature, on the other hand, represents a process never before seen on Io, Davies said: something intense, powerful, and—most important—fast.

    There’s only one likely explanation for what the instruments saw, explained Davies, whose volcanic expertise starts here on Earth. Large, violent eruptions like those seen at Stromboli are capable of spewing huge masses of tiny particles into the air, which cool quickly. See for yourself in this video of Stromboli erupting:

    As chance would have it, Galileo was likely in the right place at the right time to see the signatures of such an eruption on Io.

    Composition Questions

    Why do scientists care about an eruption on a moon nearly 630 million kilometers away?

    The temperature of Io’s lava dictates what kind of material makes up the moon, Davies said. For instance, if the rising magma erupts at temperatures of 1,800 or 1,900 K, it’s probably composed of komatiite, a rock extremely low in silicon. This rock is rarely found on Earth today, although scientists think it was commonly found during the Archaen eon 2.5–3.8 billion years ago, Earth’s early volcanic days. However, if the magma erupts at 1,400 or 1,500 K, that means it’s primarily made of basalt.

    The lava’s composition and temperature, in turn, can tell scientists what’s going on in the moon’s interior. Scientists aren’t yet sure how the push and pull from Jupiter’s gravity affect Io’s innards. Some have hypothesized that the grinding from the gravitational pull heats Io’s interior enough to produce a subsurface magma ocean.

    “Instead of being a completely fluid layer, Io’s magma ocean would probably be more like a sponge with at least 20% silicate melt within a matrix of slowly deformable rock,” said Christopher Hamilton, a planetary volcanologist at the University of Arizona’s Lunar and Planetary Science Laboratory in a prior press release about the push and pull of tidal forces on Io. Hamilton was not involved in this research.

    To help refine such hypotheses, scientists need the composition of melt and how hot it gets, Davies explained. But figuring out the precise heat of Io’s lava is tricky because regardless of its starting temperature, it cools relatively quickly. So even if the lava is made of komatiite, scientists may not be able to catch the signal before it cools to a temperature resembling that of basalt.

    The good news about large, Stromboli-type eruptions is that they expose vast areas of lava at incandescent temperatures. “So what we end up with is an event, if you can capture it, that will show a lot of lava at the temperature it erupted,” Davies said.

    Current and future probes can then home in on Marduk Fluctus for more detailed surveys to reveal such precise temperature data, Davies explained. However, until such future instruments launch, scientists still have mountains of Galileo data to get through.

    From Drone Peers into Open Volcanic Vents Further references with links:

    Bombrun, M., et al. (2015), Anatomy of a Strombolian eruption: Inferences from particle data recorded with thermal video, J. Geophys. Res. Solid Earth, 120, 2367–2387, https://doi.org/10.1002/2014JB011556.

    Burton, M., et al. (2007), Magmatic gas composition reveals the source depth of slug-driven Strombolian explosive activity, Science, 317, 227–230, https://doi.org/10.1126/science.1141900.

    Calvari, S., et al. (2016), Monitoring crater-wall collapse at active volcanoes: A study of the 12 January 2013 event at Stromboli, Bull. Volcanol., 78, 39, https://doi.org/10.1007/s00445-016-1033-4.

    Fornaciai, A., et al. (2010), A lidar survey of Stromboli volcano (Italy): Digital elevation model-based geomorphology and intensity analysis, Int. J. Remote Sens., 31, 3177–3194, https://doi.org/10.1080/01431160903154416.

    Gaudin, D., et al. (2014), Pyroclast tracking velocimetry illuminates bomb ejection and explosion dynamics at Stromboli (Italy) and Yasur (Vanuatu) volcanoes, J. Geophys. Res. Solid Earth, 119, 5384–5397, https://doi.org/10.1002/2014JB011096.

    Gaudin, D., et al. (2016), 3‐D high‐speed imaging of volcanic bomb trajectory in basaltic explosive eruptions, Geochem. Geophys. Geosyst., 17, 4268–4275, https://doi.org/10.1002/2016GC006560.

    Gurioli, L., et al. (2013), Classification, landing distribution, and associated flight parameters for a bomb field emplaced during a single major explosion at Stromboli, Italy, Geology, 41, 559–562, https://doi.org/10.1130/G33967.1.

    Harris, A. J. L., et al. (2013), Volcanic plume and bomb field masses from thermal infrared camera imagery, Earth Planet. Sci. Lett., 365, 77–85, https://doi.org/10.1016/j.epsl.2013.01.004.

    James, M. R., and S. Robson (2012), Straightforward reconstruction of 3D surfaces and topography with a camera: Accuracy and geoscience application, J. Geophys. Res., 117, F03017, https://doi.org/10.1029/2011JF002289.

    Patrick, M. R., et al. (2007), Strombolian explosive styles and source conditions: Insights from thermal (FLIR) video, Bull. Volcanol., 69, 769–784, https://doi.org/10.1007/s00445-006-0107-0.

    Rosi, M., et al. (2013), Stromboli volcano, Aeolian Islands (Italy): Present eruptive activity and hazards, Geol. Soc. London Mem., 37, 473–490, https://doi.org/10.1144/M37.14.

    Scarlato, P., et al. (2014), The 2014 Broadband Acquisition and Imaging Operation (BAcIO) at Stromboli Volcano (Italy), Abstract V41B-4813 presented at the 2014 Fall Meeting, AGU, San Francisco, Calif.

    Taddeucci, J., et al. (2007), Advances in the study of volcanic ash, Eos Trans. AGU, 88, 253, https://doi.org/10.1029/2007EO240001.

    Taddeucci, J., et al. (2012), High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts, Geophys. Res. Lett., 39, L02301, https://doi.org/10.1029/2011GL050404.

    See the full article here .

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  • richardmitnick 10:10 am on September 27, 2017 Permalink | Reply
    Tags: , Drone Peers into Open Volcanic Vents, , Fortunately robotic technology can go where humans cannot, Stromboli volcano, UAVs-Unmanned aerial vehicles,   

    From Eos: “Drone Peers into Open Volcanic Vents” 

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    9.27.17
    Nicolas Turner, Bruce Houghton, Jacopo Taddeucci, Jost von der Lieth, Ullrich Kueppers, Damien Gaudin, Tullio Ricci, Karl Kim, and Piergiorgio Scalato

    1
    Stromboli, one of the world’s most active volcanoes, ejects large, hot volcanic bombs in this long-exposure image of the northeastern region of the summit crater terrace. During a May 2016 pilot project, the authors sent unmanned aerial vehicles where humans couldn’t go to capture images and gather data on the locations and characteristics of Stromboli’s craters and vents. Credit: Rainer Albiez/Shutterstock.com

    Volcanoes that erupt frequently give researchers special opportunities to make repeated high-resolution observations of rapid eruption processes. At explosive volcanoes like Stromboli, situated just off the southwestern coast of Italy, “normal” explosive eruptions take place every few minutes to tens of minutes. However, the rainout of hot volcanic bombs, some as large as a meter across, makes it hazardous for scientists and their instruments to get close enough to Stromboli’s active vents to collect some forms of essential data.

    At volcanoes like Stromboli, we can make many key observations from safe locations, hundreds of meters from the erupting vents. Other key observations must be made from locations beside or immediately above the vents. These underrecorded observations include the exact locations of vents, their dimensions, and the depth to the magma’s free surface. These observations have generally not been feasible because explosions occur at irregular frequencies, and they seldom provide warning; our inability to make these observations has been a major impediment to our models of the eruption process.

    Fortunately, robotic technology can go where humans cannot. Unmanned aerial vehicles (UAVs) have become cheaper and more accessible, and they now have the ability to carry lightweight optical sensors for mapping and aerial observations of volcanic activity.

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    Fig. 1. (top) Digital point cloud model of Stromboli crater terrace showing the two vent areas of the crater terrace. (middle) Digital elevation models (DEMs) of the northeast and southwest vent areas showing morphology. (bottom) Classification maps of active vents, inactive vents, and fumaroles from the high-resolution DEMs, aerial imagery, and low-altitude video observations of activity for active vents and fumaroles. Inactive vents were identified by examining the DEMs for features with morphology similar to that of the active vents.

    We used a UAV in a May 2016 pilot survey campaign at Stromboli to map detailed features of the active crater terrace and produce a high-resolution digital elevation model, with details as small as about 5 centimeters. Different vent areas within this crater terrace host active and inactive vents as well as fumaroles, and the UAV helped us determine their locations and dimensions.

    What We Do Know

    There are many things scientists can observe from volcanoes without drones. For example, remote observations from closely positioned cameras and sensors can record initial velocities for the erupted particles (bombs and ash) [Patrick et al., 2007; Gaudin et al., 2016], event durations and mass eruption rates [Taddeucci et al., 2012; Rosi et al., 2013; Gaudin et al., 2014], temperature and flux of gas species [Burton et al., 2007], and the sizes of the ejected bombs [Gurioli et al., 2013; Bombrun et al., 2015 (sorry, no links)].

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    Fig. 2. A sudden shift in wind direction momentarily sweeps away a gas cloud, giving the UAV a clear view of the interior of the crater and revealing an active vent (2) and an inactive vent (3). Active vent 1 is obscured, but it lies directly behind the bluish gas plume to the left of vent 2.

    Through recent field campaigns at Stromboli, scientists have gathered excellent time-synchronized databases of geophysical data and observations of eruption timings, pulsations, and mass flux derived from seismometers, high-speed cameras, webcams, Doppler radar, and infrasound sensors [e.g., Scarlato et al., 2014]. MultiGAS instruments (which combine optical and electrochemical sensors), Fourier transform infrared spectrometers, and ultraviolet and thermal infrared cameras have captured the nature and flux of key magmatic gases (water, carbon dioxide, and sulfur gases) associated with the activity.

    These sensors, however, have their limits. UAVs, however, can push data collection beyond these limits.

    Soaring Above the Danger

    Over the past 2 decades, Stromboli has been surveyed with lidar technology, but because of the high costs involved with lidar surveys, they are not conducted frequently enough to capture rapid changes at the summit of Stromboli.

    5
    Fig. 3. The UAV captured this visible-light still frame of an expanding ash-rich explosion from the dominant vent 4. The ash plume is more than 300 meters high.

    UAV-based mapping can supplement or replace lidar surveys. UAVs, popularly known as drones, were first used at Stromboli in 2007 to collect ash samples [Taddeucci et al., 2007]. Since that time, they have become cheaper, smarter, and able to carry higher-quality imaging sensors, such as the X5 camera mounted on the DJI Inspire-1 quadcopter for our 2016 study.

    Advances in the field of computer vision have also yielded software capable of extracting 3-D topography from multiple 2-D images in a process called structure from motion. Pairing this practical technique with UAVs has resulted in widespread adoption across multiple fields in science, and volcanology is no exception [James and Robson, 2012].

    UAVs, in combination with the live webcams deployed around the crater terrace [Fornaciai et al., 2010; Calvari et al., 2016], provide an unprecedented level of monitoring via imaging and sampling eruption plumes. UAVs could even be used to deploy sensors near or inside the vent.

    What’s more, with an extended range, UAVs could allow observations when human access to the summit is forbidden and dangerous. This capability would be especially useful, for example, during the rare paroxysmal phases, which can last several months.

    Given this potential, we decided to put the utility of UAVs to the test.

    First Results

    Even UAVs face challenges like constant gas emissions, high and gusting winds, and unpredictable explosions when mapping volcanic environments like Stromboli. In the worst case, UAVs may be severely damaged, or their data may be lost.

    During our 2016 campaign, explosions proved the most challenging to cope with: On more than one occasion, the UAV was almost engulfed by a rising ash plume while it was mapping directly above an active vent. Active fumaroles constantly sent up clouds of gas, condensed water vapor, and ash particles, making it difficult for the onboard camera to get clear images of these vents for use in mapping the interior of the source craters. Fortunately, shifts in wind would briefly clear the craters, providing the camera with an occasional clear view, as seen in the video below.


    During a May 2016 mapping survey, an unmanned aerial vehicle (drone) captured this close-up view of several active vents on the slopes of Stromboli, one of the world’s most active volcanoes, situated just off the southwestern coast of Italy. Stromboli often produces explosive eruptions every few minutes, making it too hazardous for researchers to approach these vents to take data. Credit: Nicolas Turner and coauthors.

    We constructed the final maps of the crater terrace (Figure 1) by selecting the highest-quality images from more than a dozen mapping flights over 2 days. We processed the images with structure from motion software to construct a relatively gas free orthomosaic (aerial map corrected for distortions) and accompanying digital elevation model.

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    Fig. 4. The UAV captured this image of vents 2 and 5 in the northeast and southwest regions, respectively, between explosions.

    We mapped a total of 4 active vents, 11 inactive vents, and 33 fumaroles in the southwest and northeast vent areas present in May 2016 (Figure 1). There is no clear pattern to vent distribution within the larger structures on the crater terrace. Inactive vents, particularly fumaroles, tend to occur in clusters without a single, consistent orientation. The two principal northeast vents are aligned approximately east–west and are 69 meters apart. The two principal southwest vents are 55 meters apart and aligned roughly north to south.

    Overall, the northeastern active vents were similar to each other in depth and diameter (Figure 2), but the southwestern active vents were significantly deeper. Inactive vents were much shallower than active vents. During a week of observations, the southwestern vents produced the larger and more powerful explosions. Explosions from vent 4 (see Figure 1) were typically ash charged, and the free surface was generally covered by debris between successive explosions. These plumes often reached heights of several hundred meters (Figure 3).

    In contrast, an incandescent free surface was often visible in vent 5 and the active northeastern vents (see Figure 4), and in Figure 5, spattering and outgassing are clearly visible in vent 2 during a repose interval.

    7
    Fig. 5. Close-up view of vent 2 showing weak discontinuous spattering activity that continued between explosions.

    Implications for Eruption Processes and Volcano Monitoring

    This pilot survey yielded useful data, and it serves as a guide for future more ambitious and repeated deployments. The data we gathered—the precise source locations of explosions, for example—can potentially help us reduce the uncertainty in geophysical model inputs for seismic and acoustic arrays and gravity measurements.

    We hope to establish precise correlations of changing eruption style and intensity with time for single vents, along with synchronous observations of depths to the free surface of magma in the parent vents. This and future deployments will help us to monitor abrupt and progressive changes in the diameter of single vents over time and the influence of these changes on eruptive behavior.

    8
    Near-infrared picture of a bomb-bearing explosion from vent 5. Light tones denote high (incandescent) temperatures. The vertical field of view is 20.5 meters.

    Our data will assist in making comparisons of how differences in vent width and depth to the free surface, the orientation and inclination of the conduit, and the extent of debris covering the free surface all influence contrasting eruption behavior at adjacent vents.

    The ability to capture such detail at an active volcano offers the opportunity to greatly enhance programs for short-term as well as long-term volcano monitoring. Scientists modeling Strombolian eruptions can use these new data to reduce the uncertainty in numerical model input parameters (e.g., conduit and acoustic modeling).

    The low cost and safety of UAV operations allow small-scale changes to be captured and UAV surveys to be launched as frequently as necessary. These benefits make UAVs a critical complement to other remote sensing and geophysical techniques.

    Acknowledgments

    This study was supported by funding from the National Science Foundation (NSF EAR14-27357) and the VERTIGO Marie Curie ITN, funded through the European Seventh Framework Programme (FP7 2007-2013) under grant agreement 607905. We acknowledge numerous companions during the 2016 campaign at Stromboli, especially Elisabetta del Bello, Valeria Cigala, Bianca Mintz, and Pierre-Yves Tournigand.

    References

    Bombrun, M., et al. (2015), Anatomy of a Strombolian eruption: Inferences from particle data recorded with thermal video, J. Geophys. Res. Solid Earth, 120, 2367–2387, https://doi.org/10.1002/2014JB011556.

    Burton, M., et al. (2007), Magmatic gas composition reveals the source depth of slug-driven Strombolian explosive activity, Science, 317, 227–230, https://doi.org/10.1126/science.1141900.

    Calvari, S., et al. (2016), Monitoring crater-wall collapse at active volcanoes: A study of the 12 January 2013 event at Stromboli, Bull. Volcanol., 78, 39, https://doi.org/10.1007/s00445-016-1033-4.

    Fornaciai, A., et al. (2010), A lidar survey of Stromboli volcano (Italy): Digital elevation model-based geomorphology and intensity analysis, Int. J. Remote Sens., 31, 3177–3194, https://doi.org/10.1080/01431160903154416.

    Gaudin, D., et al. (2014), Pyroclast tracking velocimetry illuminates bomb ejection and explosion dynamics at Stromboli (Italy) and Yasur (Vanuatu) volcanoes, J. Geophys. Res. Solid Earth, 119, 5384–5397, https://doi.org/10.1002/2014JB011096.

    Gaudin, D., et al. (2016), 3‐D high‐speed imaging of volcanic bomb trajectory in basaltic explosive eruptions, Geochem. Geophys. Geosyst., 17, 4268–4275, https://doi.org/10.1002/2016GC006560.

    Gurioli, L., et al. (2013), Classification, landing distribution, and associated flight parameters for a bomb field emplaced during a single major explosion at Stromboli, Italy, Geology, 41, 559–562, https://doi.org/10.1130/G33967.1.

    Harris, A. J. L., et al. (2013), Volcanic plume and bomb field masses from thermal infrared camera imagery, Earth Planet. Sci. Lett., 365, 77–85, https://doi.org/10.1016/j.epsl.2013.01.004.

    James, M. R., and S. Robson (2012), Straightforward reconstruction of 3D surfaces and topography with a camera: Accuracy and geoscience application, J. Geophys. Res., 117, F03017, https://doi.org/10.1029/2011JF002289.

    Patrick, M. R., et al. (2007), Strombolian explosive styles and source conditions: Insights from thermal (FLIR) video, Bull. Volcanol., 69, 769–784, https://doi.org/10.1007/s00445-006-0107-0.

    Rosi, M., et al. (2013), Stromboli volcano, Aeolian Islands (Italy): Present eruptive activity and hazards, Geol. Soc. London Mem., 37, 473–490, https://doi.org/10.1144/M37.14.

    Scarlato, P., et al. (2014), The 2014 Broadband Acquisition and Imaging Operation (BAcIO) at Stromboli Volcano (Italy), Abstract V41B-4813 presented at the 2014 Fall Meeting, AGU, San Francisco, Calif.

    Taddeucci, J., et al. (2007), Advances in the study of volcanic ash, Eos Trans. AGU, 88, 253, https://doi.org/10.1029/2007EO240001.

    Taddeucci, J., et al. (2012), High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts, Geophys. Res. Lett., 39, L02301, https://doi.org/10.1029/2011GL050404.

    Author Information

    Nicolas Turner (email: nrturner@hawaii.edu; @nicolasrturner) and Bruce Houghton, Department of Geology and Geophysics, University of Hawai‘i at Mānoa, Honolulu; Jacopo Taddeucci, Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy; Jost von der Lieth, Department of Earth Sciences, Universität Hamburg, Germany; Ullrich Kueppers and Damien Gaudin, Ludwig-Maximilians-Universität München, Munich, Germany; Tullio Ricci, Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy; Karl Kim, National Disaster Preparedness Training Center, University of Hawai‘i at Mānoa, Honolulu; and Piergiorgio Scalato, Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
    Citation: Turner, N., B. Houghton, J. Taddeucci, J. von der Lieth, U. Kueppers, D. Gaudin, T. Ricci, K. Kim, and P. Scalato (2017), Drone peers into open volcanic vents, Eos, 98, https://doi.org/10.1029/2017EO082751. Published on 27 September 2017.

    See the full article here .

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  • richardmitnick 10:02 am on March 13, 2017 Permalink | Reply
    Tags: , , Stromboli volcano,   

    From Eos: “Tracking Volcanic Bombs in Three Dimensions” 

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    AGU
    Eos news bloc

    Eos

    3.13.17
    Leah Crane

    1
    Off the north coast of Sicily, an eruption of the Stromboli volcano sends decametric lava fragments flying into the air. A new method allows researchers to track these “bombs” and to reconstruct their flight trajectories in three dimensions. Credit: Florian Becker/Vulkankultour

    In explosive volcanic eruptions, bits of fragmented magma can be shot through the air by the release and expansion of pressurized gas. The trajectory map of these centimetric to decametric fragments, called “bombs,” is an important parameter in the study of explosive eruptions and the dangers that they present: Understanding how fast the debris is moving, how far it moves, and in which direction pieces travel could help scientists assess the hazards of volcanic eruptions or man-made explosions. In a new paper, Gaudin et al . present a method for studying the motion of volcanic bombs in three dimensions, allowing for more precise trajectory reconstructions.

    There are several conditions that make observing active volcanic vents and bombs difficult, including the obvious difficulty of getting cameras close to the vents. The most significant of the problems is the large number of bombs from each explosive event that may change shape in flight and whose flight paths overlap with one another.

    2
    When observing a bubble bursting in Halema‘uma‘u lava lake in Hawaii, researchers manually tracked selected pieces of debris on stills of a video. These two images of the resulting set of trajectories could then be combined to produce a three-dimensional map. Credit: Gaudin et al. [2016]

    These limitations make any automatic tracking difficult or impossible, so the scientists simplified their procedure by relying on manual tracking of a few representative bombs rather than a computerized account of every single one. By placing two or more high-speed video cameras at well-documented positions around the volcanic vent, they were able to manually determine an object’s location in all of the images, computing the object’s position in three dimensions.

    The human component of this manual process can be a major source of error since the person tracking the bombs makes a series of subjective choices, like deciding where exactly on the object to select as a representative point in each frame. If the cameras are tilted at all, that can also be a significant component of uncertainty in the measurements.

    In the new study, the team was able to reduce uncertainty to 10° in angle and 20% in speed of the bombs. They used three events as examples: a bursting bubble at the Halema‘uma‘u lava lake in Hawaii, in-flight bomb collision, and an explosive ejection event at Stromboli volcano in Italy. A video showing the bursting bubble followed by the explosive ejection and their model in action is given below.


    In Stromboli’s case, the reliability of the trajectory reconstruction was demonstrated by comparing the 3-D reconstruction with the low-speed, low-resolution cameras of the Stromboli permanent monitoring network. These case studies demonstrated just a few of the numerous contexts in which this 3-D tracking method could be useful, both within and beyond the study of volcanic vents and magma. (Geochemistry, Geophysics, Geosystems, https://doi.org/10.1002/2016GC006560, 2016)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

     
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