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Over what distances do volcanoes interact?

In the geological past, large eruptions have often occurred simultaneously at nearby volcanoes. Now, a team of COMET scientists from the University of Bristol uses satellite imagery to investigate the distances over which restless magmatic plumbing systems interact.

In a study published in the journal Nature Geoscience, the scientists use deformation maps from the Kenyan Rift to monitor pressure changes in a sequence of small magma lenses beneath a single volcano. Importantly, they find that active magma systems were not disturbed beneath neighboring volcanoes less than 15 km away.

The lead author, Dr Juliet Biggs, explained: “Our satellite data shows that unrest in Kenya was restricted to an individual system. Inter-bedded ash layers at these same volcanoes, however, tell us that they have erupted synchronously in the geological past. This was our first hint to compare observations of lateral interactions based on recent geophysical measurements with those from petrological analyses of much older eruptions.

The team, which includes a recently graduated PhD student Elspeth Robertson and Bristol’s Head of Volcanology Prof. Kathy Cashman, took this opportunity to compare observations from around the world with simple scaling laws based on potential interaction mechanisms. They found that stress changes from very large eruptions could influence volcanoes over distances of up to 50 km, but that smaller pressure changes associated with unrest require a different mechanism to explain the interactions.

Prof Cashman explained ‘Volcanology is undergoing a scientific revolution right now – the concept of a large vat of liquid magma beneath a volcano is being replaced by that of a crystalline mush that contains a network of melt or gas lenses. The interactions patterns observed in Kenya support this view, and help to constrain the geometry and location of individual melt and gas lenses.”

The study was funded by two major NERC projects: COMET, a world-leading research centre focusing on tectonic and volcanic processes using Earth observation techniques; and RiftVolc, which is studying the past, present and future behavior of volcanoes in the East African Rift.

The research paper, The lateral extent of volcanic interactions during unrest and eruption, was published online in Nature Geoscience on 15th February 2016.

Sentinel-1 satellite captures volcanic surface changes that reveal the flow below

Pablo Gonzalez’s work on the 2014 Pico do Fogo eruption has been featured in the AGU’s Eos magazine.

Pico do Fogo. Credit: Nicole Richter
Pico do Fogo. Credit: Nicole Richter

The research uses a new satellite imaging system to model the subsurface path of the magma that fed the eruption, and shows that Sentinel-1’s TOPS InSAR technique has the potential to be used to study other natural hazards, including earthquakes and landslides.

Read the full article at EoS

COMET heads to Santiaguito, Guatemala

Scientists from COMET are participating in a workshop, funded by the US National Science Foundation, to study Santiaguito volcano, Guatemala.

SUAS shot of an explosion at Santiaguito volcano,  January 9 2016
SUAS shot of an explosion at Santiaguito volcano, January 9 2016

Matt Watson, Luke Western and Kate Wilkins have been in Guatemala since January 2nd, acquiring data with a range of instruments including three UV camera systems, three additional mini-UV spectrometers, a multispectral infrared camera, a lightweight infrared camera and a Phantom II Small Unmanned Aerial System (SUAS).

<a href="http://tempcomet.leeds.ac site acheter viagra.uk/wp-content/uploads/2016/01/guatemala1.jpg”>SUAS selfie showing an array of IR and UV cameras
SUAS selfie showing an array of IR and UV cameras

The meeting, the first in a series of scientific and educational workshops to be held at an active laboratory volcano every two to three years, is lead by a selection of principal scientists who have different field-­based data collection expertise.

They, along with students and local scientists, conducted fieldwork just prior to the formal workshop.  During the main phase of the workshop additional participants, including other students and professionals, arrived and had an opportunity to both observe the field installations and participate in data collection.

Formal lectures, on both measurement techniques and recent findings on shallow conduit processes at Santiaguito, were given by the principal scientists on January 5th. Different groups then headed out for four days to make various observations and measurements of the volcano.

The focus for the following two days, the last of the workshop, was on breakout groups and hands‐on analysis of the multiple data types that were collected concurrently. Everyone participating in the workshop, including students and principal scientists, shared and received all the data products at the end of the workshop.

Following the workshop, analytical results, tools, and integrated products will be delivered to the participants and published electronically for the broader community.

Watson, Western and Wilkins, with Helen Thomas from Nicarnica Aviation, are now heading to both Pacaya and Fuego volcanoes. At Pacaya they hope to undertake a drone survey of the crater by adapting the Phantom II to fly the lightweight IR camera. At Fuego, they will acquire more imaging and spectral measurements of the volcano’s emissions and investigate installation of the multispectral infrared camera.

Kink in fault line below Nepal explains why Himalayas keep growing

 

An international team of scientists, led by COMET’s John Elliott, has shed new light on the earthquake that devastated Nepal in April 2015, killing more than 8,000 people.

In a study published in the journal Nature Geoscience, the scientists show that a kink in the regional fault line below Nepal explains why the highest mountains in the Himalayas are seen to grow between earthquakes.

Himalayas_JADU

Dr Elliott explained: “We have shown that the fault beneath Nepal has a kink in it, creating a ramp 20km underground. Material is continually being pushed up this ramp, which explains why the mountains were seen to be growing in the decades before the earthquake. The earthquake itself then reversed this, dropping the mountains back down again when the pressure was released as the crust suddenly snapped in April 2015.

“Using the latest satellite technology, we have been able to precisely measure the land height changes across the entire eastern half of Nepal. The highest peaks dropped by up to 60cm in the first seconds of the earthquake.”

Mount Everest, at more than 50km east of the earthquake zone, was too far away to be affected by the subsidence in this event.

The team, which included academics from the USA and France, also demonstrate that the rupture on the fault stopped 11km below Kathmandu. This leaves an upper portion that remains unbroken and will build up more pressure over time as India continues to collide with Nepal, and indicates that another major earthquake could take place within a shorter timeframe than the centuries that might be expected for the area.

Dr Elliott added: “As this part of the fault is nearer the surface, the future rupture of this upper portion has the potential for a much greater impact on Kathmandu if it were to break in one go in a similar sized event to that of April 2015.

“Work on other earthquakes has suggested that when a rupture stops like this, it can be years or decades before it resumes, rather than the centuries that might usually be expected.”

Study co-author Dr Pablo González, from the School of Earth and Environment at the University of Leeds and also a COMET member, said: “We successfully mapped the earthquake motion using satellite technology on a very difficult mountainous terrain. We developed newly processing algorithms to obtain clearer displacement maps, which revealed the most likely fault geometry at depth to make sense of the puzzling geological observations.”

The research paper, Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake, was published online in Nature Geoscience on 11 January 2016.

 

Tracking the Etna eruption

On the evening of December 2 2015, Sicily’s Mount Etna began to erupt for the first time in over two years, reaching a brief but violent climax in the early hours of December 3 which included lava fountains as well as a column of gas and ash several kilometres high. The event was among the most violent seen at Etna over the last twenty years.

Ash cloud from Mount Etna’s Voragine crater lights up the sky. Credit: Marco Restivo/Demotix/Corbis
Ash cloud from Mount Etna’s Voragine crater lights up the sky. Credit: Marco Restivo/Demotix/Corbis

Luckily, good weather meant that the eruption could be monitored with visual and thermal cameras from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) Etna Observatory.  According to INGV reports, activity peaked between 02:20 and 03:10 GMT when a continuous lava fountain reached heights well above 1km; with some jets of volcanic material reaching 3km into the sky.  Although the eruption had more or less ceased by dawn, the volcanic cloud had blown northeast, causing ash to be deposited on the nearby towns of Taormina, Milazzo, Messina and Reggio Calabria.

The eruption has so far continued, repeating the behaviour seen earlier with tall lava fountains and eruption columns many kilometers high.  Updates can be found on the INGV webpage.

COMET scientists at the University of Oxford have been tracking the volcanic plume’s progress using data from the Infrared Atmospheric Sounding Instruments (IASI) on board ESA’s MetOp-A and MetOp-B satellite platforms.  These instruments can detect the presence of volcanic SO2 in the atmosphere, using methods developed by the University’s Earth Observation Data Group.

The results, which can be found on the IASI NRT web page, showed that by Friday 4 December the plume had reached an area between Crete and Iraq, containing 0.06 Tg (1012g) SO2.

Estimate of SO2 amount from IASI-A overpass on the morning of 3 and 4 December 2015, assuming the SO2 between 9 and 10 km altitude
Estimate of SO2 amount from IASI-A overpass on the morning of 3 and 4 December 2015, assuming the SO2 between 9 and 10 km altitude

By the morning of 7 December, the plume had travelled from Sicily to Asia, reaching as far as Japan and the Pacific Ocean.

Screenshot from IASI NRT webpage 7 December 2015
Screenshot from IASI NRT webpage 7 December 2015

Dr Elisa Carboni, a COMET researcher based at the University of Oxford, said: “This is a great example of how we can track volcanic plume using the near real time IASI service. ”

You can follow the volcanic plume on the IASI NRT web page.

 

 

Volcanoes of the Ethiopian Rift Valley

Are the volcanoes of the Ethiopian Rift Valley now peaceful, or do they continue to pose a threat to the tens of millions of people who live and work the land across this vast region?

View into the Main Ethiopian Rift Valley, on the descent from Butajira to Ziway. Aluto volcano in the centre distance.
View into the Main Ethiopian Rift Valley, on the descent from Butajira to Ziway. Aluto volcano in the centre distance.

Read COMET scientist David Pyle’s blog post on the work of the NERC-funded RiftVolc consortium, which is carrying out a broad-scale investigation of the past eruptive histories, present status and potential for future activity of the volcanoes of the Central Main Ethiopian Rift.

COMET workshop on the modelling of magmatic processes

Around 20 scientists gathered at the University of Leeds recently to share their knowledge and their views on how magmatic activity can be understood and reproduced by models of volcanic processes.

Fourteen COMET members, including scientists, research staff and students, were joined by experts in various fields of volcanology from other world-leading institutions such as the United States Geological Survey, the University of Geneva and the University of Liverpool.

At the workshop we discussed the numerous challenges we face when we try to experimentally replicate natural processes such as those occurring at volcanoes. The most important limitation is that we can exclusively witness and measure what happens at the surface of the volcanoes, and only indirectly infer what goes on beneath them.

There are many different techniques commonly used to take the pulse of the magmatic activity: we measure how the volcanic edifices deform, we record seismic waves coming from and travelling through the magmatic systems, we collect and analyse lava and ash samples during eruptions, we measure the concentration of gases emitted by volcanic vents etc.

The rapid expansion and improvement of satellite Earth Observation (EO) techniques (such as radar interferometry to measure deformation, infrared atmospheric sounding to measure gas emissions etc.) offers further opportunities to study magmatic processes at a global scale.

Although each technique can shed light on one or more volcanic processes, the highest chance of truly understanding what controls the magmatic activity happens when all the measurements and information are analysed together.

The use of a multi-disciplinary approach was the key element of the COMET workshop and all participants agreed that future research in volcanology must move in this direction. Conceptual and numerical models of how magma is stored beneath the surface must be able to reconcile the observed deformation, the amount of gasses released in the atmosphere and the physical/chemical properties of the erupted products. Models of how magma reaches the surface during eruptions need to explain the seismic signature of magma ascent, be compatible with the mechanical properties of volcanic rocks, and consider magma as a multi-phase fluid containing gas, liquid and crystals.

During our workshop, we identified several potential research projects that will be developed in the coming months and that will imply the use of information from different disciplines of volcanology. For example, we aim to globally classify active volcanoes on the basis of their behaviours in terms of deformation and gas emissions. Much effort will also be put in understanding the characteristics of magma reservoirs, moving from conceptual models of simple liquid-filled cavities to complex, multi-phase, dynamic systems.

Finally, specific volcanoes where COMET scientists already have access to long records of geophysical, geochemical and petrological data (for example Soufriere Hills Volcano in Montserrat or Kilauea Volcano in Hawaii) will be used as natural laboratories. At these locations, we will test models that try to reproduce processes ranging from specific eruptive behaviours to long-term magma supply to the volcanoes.

For further information, contact Dr Marco Bagnardi m.bagnardi@leeds.ac.uk.

Multiple techniques shed light on the August 2014 Murmuri, Iran earthquake sequence

COMET researchers have unravelled a complex seismic sequence using a combination of techniques, explaining not only the earthquake sequence itself but also the formation of the mountain range where it occurred.

On August 18 2014, an Mw 6.2 earthquake struck Murmuri, near Dehloran in the Zagros Mountains of South West Iran (Figure 1), and was followed by five aftershocks of Mw of at least 5.4.  The largest of these was a Mw 6.0 aftershock which took place 16 hours after the main event.

These were the first large seismic events in the region since important developments in satellite Earth Observation (EO) have allowed us to study earthquakes in unprecedented detail, providing the potential to combine  a range of satellite-based and seismological approaches.

The study team, which included COMET scientists from Cambridge and Oxford along with colleagues from Iran, Colorado, and Canada, saw this as an opportunity to shed light not only on the Murmuri earthquake but also on how the Zagros Mountains themselves are evolving.

Figure 1 below shows the distribution of earthquakes in the region along with the 2014 Murmuri event.

Figure 1: Earthquakes and topography of the Zagros Mountains. White circles show events of magnitude 5.0 and larger (Nissen et al., 2011). The red star shows the Murmuri mainshock.
Figure 1: Earthquakes and topography of the Zagros Mountains. White circles show events of magnitude 5.0 and larger (Nissen et al., 2011). The red star shows the Murmuri mainshock.

The depth of the earthquake-generating thrust faults in the Zagros Mountains has been the subject of debate for some time.  Previous studies have disagreed on whether the faults break a thick sequence of sedimentary layers, or are confined to the underlying crystalline rocks.

Importantly, rather than using a single technique, the team combined satellite-based EO techniques with studies of the seismic waves generated by the earthquake and aftershocks.  The first step was to identify their locations, which was crucial to understanding the relationship between the ground motions detected by InSAR and the fault planes that caused the earthquakes.  They then used the results to generate models of the faults.

Modelling the seismic waves showed that all except one of the events were caused by thrust faults.  The smooth signals in the InSAR interferograms meanwhile showed that the faulting which led to the earthquake was buried deep under the surface.

Figure 2: Interferograms of the 18 August 2014 earthquake.  Each interferogram is labelled with the dates of the two SAR acquisitions in the format YYYYMMDD, and the background shading is the topography.
Figure 2: Interferograms of the 18 August 2014 earthquake.  Each interferogram is labelled with the dates of the two SAR acquisitions in the format YYYYMMDD, and the background shading is the topography.

The next question was whether the earthquakes had been caused by a single or multiple faults.  The interferograms showed distinct lobes extending to the east and southeast of the main affected area, suggesting that the displacements on the surface were caused by two if not three separate faults.

COMET’s Alex Copley, from the Department of Earth Sciences at the University of Cambridge, explained: “ We found that a single-fault model couldn’t reproduce the deformation patterns shown by the interferograms, so we investigated by applying multiple-fault models instead.”

The team modelled the faults to establish characteristics including their direction, length and angle.  When they used the interferograms alone there were a wide range of different fault parameters that could produce models that matched the data, but by including the seismic data the team could narrow down these characteristics.

Dr Copley added: “The only way we managed to work out what actually happened was by using seismological techniques, and then using these results  to interpret the satellite measurements.”

The results showed that the 18 August 2014 event involved significant slip on two planes, which produced a complex displacement pattern in the InSAR, and that there were two separate events big enough to produce surface deformation signals, hence the two lobes on the interferograms.

It also became clear that most if not all of the faulting took place in the sedimentary layers rather than the igneous rocks below, at depths of 3-9km.  The faults were also found to be longer than they were deep, which is relatively unusual – most faults tend to be more or less equal in length and depth.  This could be because changes in the mechanical properties of the rocks below stop the faults from extending any deeper.

As well as explaining the events at Murmuri, the results throw light on the large scale tectonics of the Zagros Mountains, showing which combination of tectonic forces and material properties of the rocks can give rise to the shape and deformation pattern of the mountain range.

Dr Copley summarised: “If we had used seismology or satellite measurements alone we would have failed to learn much that was new about this earthquake sequence.  Instead, our approach allowed us to shed light not only on the formation of the Zagros, but also how similar fold-thrust belts form across the globe.”

The full paper is: Copley, A., Karasozen, E., Oveisi, B., Elliott, J.R., Samsonov, S., Nissen, E.  Seismogenic faulting of the sedimentary sequence and laterally-variable material properties in the Zagros Mountains (Iran) revealed by the August 2014 Murmuri (E. Dehloran) earthquake sequence, Geophysical Journal International, 2015 doi: 10.1093/gji/ggv365

 

 

Sentinel-1A’s TOPS explains the 2014-15 Fogo eruption

COMET researchers have used the European Space Agency’s Sentinel-1A satellite to shed light on the 2014-15 eruption at Fogo, the most active volcano in the Cape Verde archipelago.

Their paper, published in Geophysical Research Letters, investigates the eruption using Sentinel-1A’s new radar acquisition mode, Terrain Observation by Progressive Scans (TOPS).

Fogo has erupted at least 26 times in the last 500 years, and this particular event lasted 81 days from November 2014 to February 2015.  It had devastating consequences for the island. Fast lava flows destroyed the villages of Portela and Bangaeria in early December 2014.

As the satellite had only been operating for a few weeks when the eruption began, this is the first study to use Sentinel-1A TOPS to investigate surface deformation associated with volcanic activity.

Lead author Dr Pablo J. González, from the University of Leeds, explained: “the study has given us a real insight into the inner workings of Fogo volcano.  It also shows the potential of Sentinel-1’s TOPS mode for monitoring volcanic activity in the future acheter du viagra.

Up until recently, the volcano had mostly been monitored by a GPS network with limited spatial coverage.  In comparison, the wide area and high spatial resolution of Sentinel-1A’s satellite images allowed the team, which included researchers from Norway, The Netherlands and Canada, to monitor ground deformation across Fogo.

Using the TOPS data, they found that during the eruption the ground surface had changed in a “butterfly” shape, characteristic for a dike intrusion (where the magma intrudes into a fissure, shouldering aside other the existing layers of rock).

Sentinel-1A ascending interferogram spanning the onset of the2014-2015 Fogo eruption (3 – 27 November 2014). Each colour fringe represents ~3 cm of ground displacement.  
Sentinel-1A ascending interferogram spanning the onset of the2014-2015 Fogo eruption (3 – 27 November 2014). Each colour fringe represents ~3 cm of ground displacement.

Models created to reproduce the observed data then showed that first of all the magma moved rapidly from depths of more than ten kilometres below the volcano’s summit.  It then moved along the dike to feed the eruption at a fissure on the southwestern flank of the volcano’s summit cone, rather than from its top.

This was backed up by the satellite data showing a lack of deformation across the whole island during the eruption, which would have suggested that it was instead being fed by an inflating/deflating magma reservoir directly beneath.

The findings will now set the direction for further research aimed at understanding the pattern of eruptions on the island, as well as assessing the stability of the entire volcanic structure.

Dr Marco Bagnardi, COMET researcher, and also co-author in this paper, added: “Our results not only show the importance of near-real time ground deformation monitoring at Fogo, they also demonstrate the potential of Sentinel-1A’s TOPS mode for monitoring geohazards more widely.”

The full paper, The 2014-2015 eruption of Fogo volcano: geodetic modelling of Sentinel-1 TOPS interferometry, is available now in Geophysical Research Letters.

Icelandic volcano’s toxic gas is treble that of Europe’s industry

A huge volcanic eruption in Iceland emitted on average three times as much of a toxic gas as all European industry combined, a new study has revealed.

Bárðarbunga eruption. Credit: John Stevenson.
Bárðarbunga eruption. Credit: John Stevenson.

Discharge of lava from the eruption at Bárðarbunga volcano, starting in August 2014, released a huge mass – up to 120,000 tonnes per day – of sulphur dioxide gas.  You can watch a video of the eruption here.

These emissions can cause acid rain and respiratory problems.

Researchers hope that their study, published by the Journal of Geophysical Research, will aid understanding of how such eruptions can affect air quality in the UK.

Dr Anja Schmidt, a COMET Associate from the School of Earth and Environment at the University of Leeds, who led the study, said: “The eruption discharged lava at a rate of more than 200 cubic metres per second, which is equivalent to filling five Olympic-sized swimming pools in a minute. Six months later, when the eruption ended, it had produced enough lava to cover an area the size of Manhattan.

“In the study, we were concerned with the quantity of sulphur dioxide emissions, with numbers that are equally astonishing: in the beginning, the eruption emitted about eight times more sulphur dioxide per day than is emitted from all man-made sources in Europe per day.”

The eruption last year was the biggest in Iceland for more than 200 years. It released a river of lava across northern Iceland, and lasted for six months.

The team, which also included COMET members Tamsin Mather, Elisa Carboni and Don Grainger from the University of Oxford, used data from satellite sensors to map sulphur dioxide pollution from the eruption. These were reproduced by computer simulations of the spreading gas cloud.

As well as being given off by volcanoes, sulphur dioxide is also produced by burning fossil fuels and industrial processes such as smelting. Man-made sulphur dioxide production has been falling since 1990, and was recorded at 12,000 tonnes per day in 2010.

Further information

The research was funded by the Natural Environment Research Council (NERC) and the Royal Society of Edinburgh.

The study, ‘Satellite detection, long-range transport and air quality impacts of volcanic sulfur dioxide from the 2014-2015 flood lava eruption at Bárðarbunga (Iceland)’, is published by the Journal of Geophysical Research.