GeoLog

eruption

Imaggeo on Mondays: In the belly of the beast

In the belly of the beast . Credit: Alexandra Kushnir (distributed via imaggeo.egu.eu)

Conducting research inside a volcanic crater is a pretty amazing scientific opportunity, but calling that crater home for a week might just be a volcanologist’s dream come true, as Alexandra postdoctoral researcher at the Institut de Physique du Globe de Strasbourg, describes in this week’s Imaggeo on Mondays.

This picture was taken from inside the crater of Mount St Helens, a stratovolcano in Washington State (USA). This particular volcano was made famous by its devastating explosive eruption in 1980, which was triggered by a landslide that removed most of the volcano’s northern flank.

Between 2004 and 2008 Mount St Helens experienced another type of eruption – this time effusive (where lava flowed out of the volcano without any accompanying explosions). Effusive eruptions produce lava flows that can be runny (low-viscosity) like the flows at Kilauea (Hawaii) or much thicker (high viscosity) like at Mount St Helens. Typically, high viscosity lavas can’t travel very far, so they begin to clump up in and around the volcano’s crater forming dome-like structures.  Sometimes, however, the erupting lava can be so rigid that it juts out of the volcano as a column of rock, known as a spine.

The 2004 to 2008 eruption at Mount St Helens saw the extrusion of a series of seven of these spines. At the peak of the eruption, up to 11 meters of rock were extruded per day. As these columns were pushed up and out of the volcanic conduit – the vertical pipe up which magma moves from depth to the surface – they began to roll over, evoking images of whales surfacing for air.

‘Whaleback’ spines are striking examples of exhumed fault surfaces – as these cylinders of rock are pushed out of the volcano their sides grind against the inside of the volcanic conduit in much the same way two sides of a fault zone move and grind past each other. These ground surfaces can provide scientists with a wealth of information about how lava is extruded during eruption. However, spines are generally unstable and tend to collapse after eruption making it difficult to characterize their outer surfaces in detail and, most importantly, safely.

Luckily, Mount St Helens provided an opportunity for a group of researchers to go into a volcanic crater and characterise these fault surfaces. While not all of the spines survived, portions of at least three spines were left intact and could be safely accessed for detailed structural analysis. These spines were encased in fault gouge – an unconsolidated layer of rock that forms when two sides of a fault zone move against one another – that was imprinted with striations running parallel to the direction of extrusion, known as slickensides. These features can give researchers information about how strain is accommodated in the volcanic conduit. The geologist in the photo (Betsy Friedlander, MSc) is measuring the dimensions and orientations of slickensides on the outer carapace of one of the spines; the southern portion of the crater wall can be seen in the background.

Volcanic craters are inherently changeable places and conducting a multi-day field campaign inside one requires a significant amount of planning and the implementation of rigorous safety protocols. But above all else, this type of research campaign requires an acquiescent mountain.

Because a large part of Mount St Helens had been excavated during the 1980 eruption, finding a safe field base inside the crater was possible. Since the 2004-2008 deposits were relatively unstable, the science team set up camp on the more stable 1980-1986 dome away from areas susceptible to rock falls and made the daily trek up the eastern lobe of the Crater Glacier to the 2004-2008 deposits.

Besides being convenient, this route also provides a spectacular tableau of the volcano’s inner structure with its oxidized reds and sulfurous yellows. The punctual peal of rock fall is a reminder of the inherent instability of a volcanic edifice, and the peculiar mix of cold glacier, razor sharp volcanic rock, and hot magmatic steam is otherworldly. That is, until an errant bee shows up to check out your dinner.

By Alexandra Kushnir, postdoctoral researcher at the Institut de Physique du Globe de Strasbourg, France.

This photo was taken in 2010 while A. Kushnir was a Masters student at the University of British Columbia and acting as a field assistant on the Mount St Helens project.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Imaggeo on Mondays: “Vancouver! Vancouver! This is it!”

Mount St Helen's, Washington, seen from Johnston Ridge.

On May 18th 1980 Mount St Helens (an active stratovolcano of the Cascades located in the North West US), erupted explosively following a magnitude 5.1 earthquake. The quake triggered a devastating landslide which swept away the volcano’s northern flank – in what is the largest debris avalanche recorded on Earth to date. Removal of a section of the edifice depressurised the volcano’s magmatic system triggering powerful lateral eruptions, which removed the top 300 m of the volcano.

In total, 57 people lost their lives, 250 homes were destroyed and the local infrastructure, including bridges, highways and railways, were badly damaged. Prior to the eruption, the flanks Mount St Helens and its surrounding areas were covered in a dense forest. Following the lateral blasts, all trees within a 10 km radius of the volcano were obliterated, while those further afield were badly scorched.

Andy Smedley, an atmospheric scientist, visited Mount St Helens recently, as part of a road trip around Washington and Oregon states.

“What I can tell you is that the scale is still fairly awe-inspiring, as is the devastation still evident on the ground,” he says of his visit to this extraordinary mountain. “The image in question was taken from the Johnston Ridge, which is named after David Alexander Johnston,” goes on to say Andy.

At the time of the eruption, Johnston was a volcanologist with the United States Geological Survey, in charge of volcanic-gas studies and spent long hours working on the flanks of the volcano. On the morning of the eruption he was one of the first geologists on the mountain. Observing the volcano from what he though was a safe distance (10 km from the vent), upon a ridge know at the time as Coldwater II, Johnston was one of the first to report the eruption: “Vancouver, Vancouver! This is it!” He was swept away by the lateral blast shortly after.

Alongside his USGS colleagues, Johnston was pivotal in ensuring the area around Mount St Helens remained closed to the public after unrest at the volcano was detected in early 1980. The data Johnston collected in the run-up to the devastating blast was crucial to unravelling the processes which governed the eruption.

Coldwater II has since been renamed to Johnston Ridge in memory of the dedicated geologist. There is also a visitor centre, with the same name, from which Andy took this impressive photo of Mount St. Helens.

“The peak is about 6 miles away from the camera and there’s very little vegetation that’s returned in the intervening 36 years [since the eruption],” describes Andy “you get some sense of the size of the eruption from the debris flows down the front flanks of the mountain, but it’s also worth pointing out the new lava dome building and Crater Glacier, one of the youngest glaciers on Earth, both within the 1980 crater.”

“Though it can’t be seen in the image, another thing that struck me was the extent of the blast – it can still be clearly seen by the ranks of toppled tree trunks pointing away from Mount St Helens that surround the nearby hills and extend for some miles on the drive up.”

As volcanic eruptions go, Mount St Helen’s wasn’t particularly large (VEI 5), but Andy thinks it’s relative proximity to centres of population in Washington State and Oregon made it stand out in the public’s consciousness.

“It’s not often that the contiguous USA experiences such a full on eruption (I think the nearby Lassen Peak was the last in 1915), and to have it right there on people’s doorsteps, with the ash column eventually blowing across several states, seemed to make its mark.”

By Laura Roberts, EGU Communications Officer

 Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Imaggeo on Mondays: A Bubbling Cauldron

Imaggeo on Mondays: A Bubbling Cauldron

Despite being a natural hazard which requires careful management, there is no doubt that there is something awe inspiring about volcanic eruptions. To see an erupting volcano up close, even fly through the plume, is the thing of dreams. That’s exactly what Jamie  Farquharson, a researcher at Université de Strasbourg (France) managed to do during the eruption of the Icelandic volcano Bárðarbunga. Read about his incredible experience in today’s Imaggeo on Monday’s post.

The picture shows the Holuhraun eruption and was taken by my wife, Hannah Derbyshire. It was taken from a light aircraft on the 11th of November of 2014, when the eruption was still in full swing, looking down into the roiling fissure. Lava was occasionally hurled tens of metres into the air in spectacular curtains of molten rock, with more exiting the fissure in steady rivers to cover the surrounding landscape.

Iceland is part of the mid-Atlantic ridge: the convergent boundary of the Eurasian and North American continental plates and one of the only places where a mid-ocean ridge rears above the surface of the sea. It’s situation means that it is geologically dynamic, boasting hundreds of volcanoes of which around thirty volcanic systems are currently active. Holuhraun is located in east-central Iceland to the north of the Vatnajökull ice cap, sitting in the saddle between the Bárðarbunga and Askja fissure systems which run NE-SW across the Icelandic highlands.

Monitored seismic activity in the vicinity of Bárðarbunga volcano had been increasing more-or-less steadily between 2007 and 2014. In mid-August 2014, swarms of earthquakes were detected migrating northwards from Bárðarbunga, interpreted as a dyke intruding to the east and north of the source. Under the ice, eruptions were detected from the 23rd of August, finally culminating in a sustained fissure eruption which continued from late-August 2014 to late-February of the next year.

My wife and I were lucky enough to have booked a trip to Iceland a month or so before the eruption commenced and, unlike its (in)famous Icelandic compatriot Eyjafjallajökull, prevailing wind conditions and the surprising lack of significant amounts of ash from Holuhraun meant that air traffic was largely unaffected.

At the time the photo was taken, the flowfield consisted of around 1000 million cubic metres of lava, covering over 75 square kilometres. After the eruption died down in February 2015, the flowfield was estimated to cover an expanse of 85 square kilometres, with the overall volume of lava exceeding 1400 million cubic metres, making it the largest effusive eruption in Iceland for over two hundred years (the 1783 eruption of Laki spewed out an estimated 14 thousand million cubic metres of lava).

Numerous “breakouts” could be observed on the margins of the flowfield as the emplacing lava flowfield increased in both size and complexity. Breakouts form when relatively hot lava, insulated by the cooled outer carapace of the flow, inflates this chilled carapace until it fractures and allows the relatively less-viscous (runnier) interior lava to spill through and form a lava delta. Gas-rich, low-viscosity magma often results in the emission of high-porosity (bubbly) lava. My current area of research examines how gases and liquids can travel through volcanic rock, a factor that is greatly influenced by the evolution of porosity during and after lava emplacement.

Flying through the turbulent plume one is aware of a strong smell of fireworks or a just-struck match: a testament to the emission of huge volumes of sulphur dioxide from the fissure. Indeed, the Icelandic Met Office have since estimated that 11 million tons of SO2 were emitted over the course of the six-month eruption, along with almost 7 million tons of CO2 and vast quantities of other gases such as HCl. These gases hydrate and oxidise in the atmosphere to form acids, in turn leading to acid rain. The environmental impact of Holuhraun as a gas-rich point source is an area of active research.

By Jamie Farquharson, PhD researcher at Université de Strasbourg (France)

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Lusi from the sky with drones

Lusi from the sky with drones. Credit: Giovanni Romeo, Adriano Mazzini and Giuseppe Di Stefano. (distributed via imaggeo.egu.eu)

Lusi from the sky with drones. Credit: Giovanni Romeo, Adriano Mazzini and Giuseppe Di Stefano. (distributed via imaggeo.egu.eu)

The picture shows a spectacular aerial view of a sunset over the Lusi mud eruption in East Java, Indonesia. Here thousands of cubic meters of mud, are spewed out every day from a 100 m sized central crater. Since the initial eruption of the volcano in 2006, following a 6.3 M earthquake, a surface of about 7 km2 has been covered by boiling mud, which has buried more than 12 villages and resulted in the displacement of 40,000 people.

Monitoring Lusi is part of multidisciplinary project called Lusi Lab, which focuses on the study of the behaviour of this incredible mud eruption. Many unsolved questions remain: What lies beneath Lusi? Research focuses on trying to ascertain what triggers the mud eruptions. One key question is whether Lusi is truly a mud volcano, or is it connected to a hydrothermal system linked to the nearby Arjuno Welirang volcanic complex? Lusi erupts mud, water, gas and clasts in pulses and scientists do not fully understand how the intermittent activity is linked to the seismic activity of the neighbouring volcanic complex. For the purposes of hazard and risk management, much speculation has focused on how long is the activity at Lusi is likely to last.

In an attempt to shed light on some of these questions the Lusi Lab team continually collect water and gas samples from the volcano, as well as assessing the seismic activity in the region ( including the neighbouring volcanic arc) through the deployment of a network of seismometers. This data gathering effort is further supported by a UAV prototype: The Lusi drone (assembled and equipped by INGV, Rome). The drone is able to access extreme environments and can provide photogrammetric and thermal images, gas and mud sampling and contact temperature measurements. A permanently installed Gopro Hero3 camera provides a continuous recording over the mud flows during flights, including this week’s Imaggeo on Mondays image.  Gas and water samples collected from the crater site revealed that Lusi is part of a Sedimentary Hosted Geothermal System (SHGT) that connects Lusi with the neighbouring Arjuno Welirang volcanic complex that can be seen in the background of the picture. The eruption site is continuously fed by new surges of geothermal fluids released from the volcano in particular after frequent seismic events occurring in the subduction zone in southern Java.

By Laura Roberts Artal and Giovanni Romeo 

To learn more about Lusi take a look at this paper:

Mazzini, A., Etiope, G., and Svensen, H. (2012), A new hydrothermal scenario for the 2006 Lusi eruption, Indonesia. Insights from gas geochemistry: Earth and Planetary Science Letters, 317-318. 0, 305-318.

If you pre-register for the 2015 General Assembly (Vienna, 12 – 17 April), you can take part in our annual photo competition! From 1 February up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

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