VolcanicDegassing

VolcanicDegassing

A Portmanteau of Natural Hazards

Last week, the UK’s Natural Environment Research Council (NERC) launched an over-arching programme in Natural Hazards, a network called PURE (Probability, Uncertainty and Risk in the Environment). This post is a very short attempt to navigate the maze of acronyms of projects that are either linked to PURE, or to other related initiatives in Natural Hazards in the UK.

PURE itself is a network, with funding for four years to support a range of activities in the natural hazards, mainly directed towards knowledge exchange and engagement with industry and policy-makers. PURE includes elements of the RCUK (Research Councils UK) Knowledge Transfer Networks in Financial Services (FSKTN) and Industrial Mathematics (IMKTN).

PURE also includes two major research consortia: RACER (Robust Assessment and Communication of Environmental Risk) and CREDIBLE (Consortium on Risk in the Environment: Diagnostics, Integration, Benchmarking, Learning and Elicitation), neither of which has a website as yet, but I’ll link to those when they are up.  The remit of PURE spans the spectrum of (physical) natural hazards ( including floods, extreme weather, tsunami, earthquakes and volcanic activity), while mainly focussing on UK or European case studies.

PURE intersects with another set of large-scale activities which have been jointly funded by the NERC and the Economic and Social Research Council (ESRC), under a programme called Increasing Resilience to Natural Hazards (IRNH). Most of the investment under this programme will be going into two international multi-partner consortia. Earthquakes without Frontiers (EwF) focusses on improving resilience in earthquake-prone regions of the Alpine-Himalayan mountain belt; while STREVA (Strengthening Resilience in Volcanic Areas) is a partnership with volcano observatories and other agencies in the Caribbean, Ecuador and Colombia. I wrote a little about STREVA‘s kick-off meeting on Montserrat in an earlier post. Both EwF and STREVA will shortly be supported by the appointment of two Knowledge Exchange Fellows, whose remits are likely to include bridging the gap between science and policy in natural hazards and risk both overseas, and in the UK. The call for KE Fellows is open until 12 February 2013.

Got that?  Do let me know if I have missed anything, and I shall update the post.

Links to information about the RCUK-funded Natural Hazards Consortia and Networks

A portmanteau is type of large suitcase

Santiaguito Volcano: Ninety Years and Counting.

Santiaguito Volcano: Ninety Years and Counting.

Santiaguito volcano, Guatemala, burst into life in 1922 and is now the second longest continuing eruption. It has outlasted both Stromboli (Italy) and Sangay (Ecuador), both erupting since 1934, and is only outdone by Yasur (Vanuatu), which has been erupting at least since 1774, when first visited by Captain Cook.

These long-lived eruptions give us an unusual opportunity to use the slowly-extruded products to peer deep into the magma plumbing system. Santiaguito itself is now a rubbly complex of blocky lavas and domes that nestle in the crater formed by the explosive destruction of Santa Maria volcano, Guatemala, in 1902, in one of the largest eruptions of the last century.

View of the lava domes of Santiaguito volcano, from the flanks of Santa Maria, Guatemala

View of the lava domes of Santiaguito volcano, from the flanks of Santa Maria, Guatemala

After a violent beginning, Santiaguito has grown slowly (rather less than 1 cubic metre of lava/second) and in pulses for the past 90 years. Bill Rose, who has worked on Santiaguito since the early 1970’s, has documented this history very nicely. For many years, Santiaguito has been a magnet for geophysical and remote-sensing field campaigns, both because of its rather regular ash and gas explosions, and the fact that it is relatively accessible and very closely monitored by INSIVUMEH.  Rather less obligingly, though, the volcano is often cloud-bound by mid-morning, at least during the dry season, when moist westerly winds roll in from the Pacific.

IMG_5235

Explanatory poster, showing the fuming dome of Santiaguito sitting in the scar of the 1902 eruption crater, Santa Maria.

While Santiaguito has only a very slow growth rate, at the lower end of what is typical of actively-extruding domes, it poses major hazards to a number of local communities.

View of the Caliente dome, Santiaguito volcano, Guatemala

View of the Caliente dome, Santiaguito volcano, Guatemala

Lahars are common in the rainy season, and transport the accumulated loose talus from the flanks of the domes downstream, intermittently causing severe damage. Ash deposition can cause disruption to a wider community, extending both to the Fincas and cloud-forest coffee plantations or, more rarely, to agricultural and urban centres further afield, such as Xela (Quetzaltenango).

This way please.. coffee-bean receptor at Finca el Faro, on the flanks of Santa Maria volcano, Guatemala.

This way please.. coffee-bean receptor at Finca el Faro, on the flanks of Santa Maria volcano, Guatemala.

Receny years have seen several episodes of elevated activity at the volcano, and in this past week, Santiaguito has experienced another such phase. As reports from CONRED make clear, this elevated activity culminated in a large-scale slope failure from the active dome, Caliente, triggering pyroclastic flows and lofting ash plumes high into the atmosphere. The rainy-season legacy of these events will most likely be more lahars, as drainages now charged with debris become unclogged and rapidly incised.

Typical deeply-incised drainage channel, high up on slopes of Santiaguito, with recent ash fall on the vegetation.

Typical deeply-incised drainage channel, high up on slopes of Santiaguito, with recent ash fall on the vegetation.

My own interest in Santiaguito is in the long-term story of the volcanic plumbing system recorded in the rocks that have been progressively removed from the conduit during the eruptions of the past 90 years. Jeannie Scott has recently completed a study of this for her PhD (funded by NERC), working on samples that span much of the eruption history. The remarkable feature is the surprisingly simple story that emerges.  The 1902 eruption evacuated a large volume of dacite magma with a silica content of about 66 wt%. The 1922 eruption appears to have begun by emptying what was left behind of this pool of melt from 1902, and since then the volcano has been erupting increasingly silica-poor magmas, presumably tapping deeper into the plumbing system. The latest lavas analysed (from 2002) have about 62% SiO2. These observations suggest that future lavas may continue to get progressively more silica-poor; as they do so, they may also get warmer and a little less viscous, depending on conditions at depth. Unfortunately, in the process of slow extrusion, the lavas lose much of their dissolved gas, crystallise and eventually quench, so that it is quite a challenge to track back to the ‘original’ conditions under which the magmas were stored. This still leaves several unresolved puzzles: how is it that the conduit system can remain open, allowing magma to continue to leak out to the surface? And what is it that drives the long-term pulses of eruptive activity?  Answers to these questions will probably emerge once we have a better understanding of the full spectrum of long-lived dome-forming eruptions at andesitic volcanoes, such as those at Soufriere Hills (Montserrat), Colima (Mexico) and Merapi (Indonesia).

Links to further reading:

JAJ Scott et al., 2013, Geochemistry and evolution of the Santiaguito volcanic dome complex, Guatemala, Journal of Volcanology and Geothermal Research 252, 92-107.

JAJ Scott et al., 2012, The magmatic plumbing system beneath Santiaguito volcano, Guatemala, Journal of Volcanology and Geothermal Research, 237–238, 54–68.

Update: February 2013.

Jeannie Scott has now written and made freely available a colour booklet describing Santiaguito volcano and its activity, and a poster summarising recent work on the volcano.

Polygons, columns and joints

Over on her Georney‘s blog, Evelyn Mervine has recently posted a nice piece with some spectacular images of columnar jointing. This seemed like a good opportunity to dust off some field photos, with some more examples of polygonal joint sets in lavas from a variety of settings, to illustrate the diversity of forms that cooling-contraction joints may take in volcanic rocks.

The first example is a late Pleistocene lava flow from the Afar, Ethiopia.

Image

Berihu Abadi, with an example of columnar jointing in a late Pleistocene basalt, Afar, Ethiopia, exposed in the face of recently-opened fracture. Fieldwork carried out as part of the NERC-funded Afar consortium.

Young lavas in the Afar are predominantly fissure-fed basalts, erupted across the topography and air-cooled. Columnar jointing is pervasive in the upper surfaces of these young lava flows, and seems to develop immediately beneath the surficial glassy and vesicular crust that forms on the top surfaces of the modern lava flows.

Image

Uppermost surface of a fresh basaltic lava flow, Afar, Ethiopia. Field of view is about 30 cm. Beneath the surface layer formed by the scales of glassy, vesicular lava, the lava is weakly polygonally-jointed (not visible in this picture). Fieldwork carried out as part of the NERC-funded Afar consortium.

Moving across to Europe, and southern Spain. Here, in the Cabo de Gata, there are some fabulous examples of polygonally-jointed andesitic lava domes, emplaced in a shallow submarine environment. These are Miocene in age, and formed in a transient volcanic arc, which has now been faulted against the Spanish mainland.

At Playa Monsul, polygonally-jointed dykes can be found criss-crossing a fabulous series of hyaloclastite bodies. Monsul is also well known as the location in Indiana Jones and the Last Crusade, where Sean Connery fends off an aerial attack with the help of an umbrella and a flock of seagulls.

Image

Polygonal jointing in the vertical face of a dyke, intruding a submarine sequence of wet sediment and hyaloclastite lavas. Polygons are typically 10-20 cm across. Photograph taken on a University of Oxford undergraduate field trip.

The southern-most cape of the Cabo de Gata has a wealth of collonaded andesites; presumably submarine domes.

Image

Columnar joints in an andesite ‘dome’ of Miocene age, southernmost Cabo de Gata, Spain. This locality offers some spectacular views both of polygonal joints in planform, and also large-scale structures showing the fanning of columns that reveal the orientations of the original cooling surfaces. Location visited on an undergraduate field trip.

The final examples of polygonal jointing come from higher (southerly) latitudes, and higher elevations, where jointing has developed as a result of ice- or snow-contact volcanism. The first example is from the flanks of volcano Osorno, Chile, where characteristic hackly jointing has developed on the outer margins of an andesitic lava flow. This differs from the regular pattern typical of columnar jointing, and is thought to be one characteristic of rapid quenching of lava.

Image

Jose Naranjo, SERNAGEOMIN, and the hackly-jointed lavas from volcan Osorno, Chile. Fieldwork carried out as part of a NERC-funded project by Sebastian Watt.

A little further South, again in Chile, and here is another classic example of a small sub-glacial ridge of andesite, this time near the summit of volcan Apagado, on the Hualaihue peninsula.

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Complex polygonal jointing in a ridge of andesite, from the margins of volcan Apagado, Chile. Fieldwork carried out as a part of a NERC-funded PhD project by Sebastian Watt.

A final example is from volcan Sollipulli, a little further North in the Chilean Lake District. This example is of a dyke, thought to have intruded along the contact between a glacier and the volcanic edifice, near the present-day crater edge. Here, the portion of the dyke that was originally in contact with the ice has developed a very strong platy fabric, and is falling apart to form a scree of what looks like slate.

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Platy jointing developed in the margins of an originally ice-bounded dyke, volcan Sollipulli, Chile. View from above, looking down the dyke margin. Platy scree now partially fills the channel which was once filled with ice. View – about 1 m across. Fieldwork was carried out as a part of a IAVCEI-funded project on the hazards of snow-capped volcanoes.

While there is general agreement that these patterns of jointing form because of the contraction of magma as it cools, there is not yet a concensus model for what it is that controls the size of the polygonal joints, or the typical number of sides. Theoretically, it is argued that a hexagonal jointing pattern would be the lowest-energy, and favoured, solution. But in reality, cooling rates might be too fast for full energy minimisation, and this might explain why many polygonal joints have fewer than six sides. This is the conclusion of the most complete study to date, in which Gyoergy Hetenyi and colleagues argue that field evidence points to two major controls being the size of the cooling body, which influences how fast it cools, and composition, which influences the physical properties of the cooling magma.

Chilean volcanoes: shaken, but not always stirred?

November 7th marked the 175th anniversary of one of the largest earthquakes to have struck northern Patagonia. The earthquake, which is estimated to have had a magnitude of 8, had an epicentre close to Valdivia, and was accompanied by significant ground shaking and subsidence as far south as Chiloe island, and a major tsunami that reached Hawaii.  The eyewitness reports of the time have been well documented. From a geological perspective, the key feature of the 1837 earthquake is that it occurred along a section of the plate boundary that has ruptured repeatedly, with great earthquakes in 1575, 1737 and, most significantly, in 1960  – which, with a magnitude of 9.5, is still the largest recorded earthquake globally. The 1837 earthquake struck just two years after the great Concepcion earthquake, of February 1835, which was exquisitely documented by Charles Darwin, among others.  Because of the location, adjacent to the long southern Chilean volcanic arc, and the frequency of large earthquakes in this region, both the 1835 and 1837 earthquakes have become critical pieces of evidence for the ongoing question of whether, and how, large earthquakes might lead to small triggered volcanic eruptions. Historical records from the region that include maps, expedition reports and navigational charts mean that the record of past eruptions in the southern parts of the central valley of Chile extend back into the 16th century and the earliest Spanish colonists.

Osorno map view from 1747

Map of southern Chile, and the northern part of Chiloe island extracted from ‘A new and accurate map of Chili, Terra Magellanica, Terra del Fuego etc.’ compiled by Emanuel Bowen in 1747. Active volcanoes of Osorno (vul. of Osorno) and, probably, Hornopiren (vul. of Quechucabi) are shown. From the Bodleian libraries, University of Oxford.

The 1837 Valdivia earthquake was followed by reported eruptions, on the same date, both at volcan Osorno, and Villarrica. Both volcanoes had already been in a state of activity on and off in the months or years prior to the earthquake, and both have long historical records of activity, so the observations are not necessarily surprising. One of the challenges of testing for cause and effect when it comes to possible earthquake-triggered eruptions is the likelihood of false reporting that arises from the natural tendency of people to conflate all sorts of observations and speculations in the aftermath of major events, like earthquakes. For example, both Villarrica and Osorno have also been recorded as having erupted shortly after the great earthquake of 1575, but neither observation is necessarily secure.

Volcan Osorno, overlooking Lago Llanquihue, Chile

Volcan Osorno, overlooking Lago Llanquihue, Chile

In contrast to the reports from 1837, the 1960 earthquake did not appear to have any major consequences for either system. Osorno has now been dormant since the late 19th century, while activity at Villarrica has rumbled on into the 21 st century.

Volcan Villarica, map view from 1759

Map of volcan Villarrica, from 1759. Reproduced in ‘Cartografia hispano colonial de Chile’, published in 1952 to mark the centenary of the birth of Don Jose T Medina. From the Bodleian libraries, University of Oxford.

Volcan Villarrica

Volcan Villarrica, with steam plume, viewed from Pucon.

Work is still in progress to investigate the consequences of the most recent great earthquake in the region: the Maule earthquake of February 2010. It remains possible that reported changes in activity at Villarrica in March 2010, seen in thermal infra-red satellite imagery, and subsequent eruptions of Planchon-Peteroa and Puyehue – Cordon Caulle may ultimately be linked to the rejuvenating effects of the earthquake, but this remains to be properly tested.

Of course, this is a question that is mainly of academic interest (in terms of understanding how eruptions are triggered), since most of the eruptions documented to have occurred in the immediate aftermath of great earthquakes are very small, and are most likely to occur at systems which have already been in eruption. The consequences of these eruptions are usually negligible, compared to the effects of the large earthquakes themselves. In recognition of the frequency of these potentially devastating earthquakes, the Chilean authorities (ONEMI, Oficina Nacional de Emergencia) are today holding an earthquake simulation across the schools of Santiago, as part of the programme of national preparedness for future emergencies.

Montserrat: Open for Business

One of the great privileges of working on volcanoes is that you get the chance to visit some amazing places, and to meet some extraordinary people. Recently, I got the chance to return to Montserrat, a small volcanic island in the Caribbean which has been the site of a dome-forming eruption since July 1995. I had first visited Montserrat in early 1998, when I had a short tour as one of the staff scientists at the Montserrat Volcano Observatory which, at that time, was temporarily located in the north of the island.

In my report for the Cambridge Evening News for the first week of February 1998, I wrote ‘Montserrat’s volcano coughed back to life this week, and reminded us of its ability to make the lives of thousands of people miserable. Every eight hours there were pulses of earthquakes as avalanches of rock fell from the dome. None of these earthquakes was large enough to be felt, but during each pulse of activity vast orange-grey clouds of dust or ash rose from the volcano. These clouds drifted across the island, sprinkling everything with gritty powder. As the clumps land they break up into tiny dust particles which form an irritating, choking haze that coats everything with a stubborn grey film. In the space of two days, fifty thousand tonnes of ash smothered the island under a layer of what looks like cement powder.’ 

Ash clouds rising from the Soufriere Hills volcano, Montserrat, February 1998

At that time, the eruption was in its third year, and no-one really had much of an inkling of how long the activity might continue. The capital of Montserrat, Plymouth, had been permanently evacuated two years earlier and, by early 1998, the edge of the ‘exclusion zone’ extended well into the north of the island, leaving the communities of Salem, Olveston and Old Towne like ash-coated ghost towns.

Air-quality sampling during an ash fall, Montserrat, February 1998. Dr Lucy Ritchie in the driving seat.

Fourteen years on, I returned to Montserrat for the first time since 2000 for the initial workshop of an ambitious project called  ‘Strengthening Resilience in Volcanic Areas’ (STREVA), which brings together physical and social scientists from universities, observatories and research institutes from five (or more) countries.  Montserrat is a key place for us to start to begin to understand the factors (physical, social, societal, cultural, economic…) that influence how people and communities respond to, recover from and learn to live with volcanic eruptions.

A lot has changed on Montserrat in the intervening years. The eruption has continued, in pulses and pauses, and, if anything, it appears to have settled into a pattern of behaviour that is both familiar, and that can be lived with. Outside the immediate perimeter of the volcano, and the debris-strewn fans that tumble down its sides, much of the landscape has recovered. Salem and adjoining communities have been open for the past decade, and a purpose-built volcano observatory now occupies a prominent viewpoint overlooking the steaming volcano.  The island is green and vibrant and, even in the once-suburban areas that were last occupied seventeen years ago, gardens are splashed with the rich reds of bougainvillea and hibiscus. A quick comparison of the airport at Gerald’s (today, below),

The airport at Geralds, Montserrat, 2012

and the helipad that preceded it (in 1998, below) just gives a hint of how the physical infrastructure of the island has developed in recent years.

The helipad at Geralds, 1998. Dr Paul Cole (currently Director of the Montserrat Volcano Observatory) prepares for an observation flight.

‘Montserrat is open for business’ was the message from the current Governor of the island, Adrian Davis, as he opened the workshop. There are ambitious plans for the future, building new capacity for tourists and other activities in the north of the island, which has only occasionally been directly affected by the volcanic activity. But the strongest evidence for the strength of resolve of the residents of Montserrat, and of the bright signs for the future, came from the stories of those who lived through the darkest days of the eruption. In some of the most captivating and emotional talks I have been privileged to listen to, speaker after speaker took the audience on their personal journeys of survival and resilience. One common theme that came across was the role played by music in coping with the distress, hardship and loss experienced by communities across the island. Herman ‘Cupid’ Francis, was a teacher before the eruption, and is now three-time Calypso Monarch and Montserrat’s Director of Culture. He summed up the spirit of 1996, the height of the crisis when people were being displaced from their homes and livelihoods, with his song ‘when you go don’t go too far .. take the road that leads you home’.

An update on Santorini

As you may have heard by now, Santorini volcano has recently been showing some unrest. Of course, it has only just come to the attention of the media, some of which have taken things a little further than can be justified.  But for those of us involved in the work, this is a story which has taken rather longer to piece together.

In my own case, the story started 26 years ago this week, when I first stepped onto Santorini during the first few days of my PhD research. Santorini was hot, dusty and felt rather exotic as it was my first taste of Greece. These steps launched me into my research career in volcanology and culminated, as I thought at the time, with the publication of the ‘Santorini Memoir‘, which summarised our reconstruction of the volcanic history of the islands over the past 600,000 years or so. But Santorini is such an iconic place to visit, and the geology is just so well laid out, that there always were reasons to return. So when a new PhD student, Michelle Parks, arrived looking for a project that would involve both ‘remote sensing’ (in this case, satellite observation) with field work on a volcano, Santorini was the obvious choice for a study of how volcanoes behave in between eruptions. In Santorini’s case, the last very small eruption was in 1950, but there was a rich record of carefully observed eruptions stretching back to 1707: a gold mine of information from which  we could tease out ideas about how it might behave in the future. When we started work in early 2010, there had been no sign at all of any life in the volcano for as long as anyone could remember.

Three years on, and that has now all changed: the volcano has just had its first ‘sharp intake of breath‘ since the last eruption, with the arrival of a fresh pulse of molten rock into the shallow crust, four or five kilometers beneath the volcano. In the time it took for the scientific paper to pass through the peer review system the rumble of tiny earthquakes which heralded this period of unrest has quietened down, and the volcano seems to be returning to slumber for just a little longer. This time, though, everyone is watching.

References.

Hooper, A., 2012, Volcanology: a volcano’s sharp intake of breath. Nature Geoscience 5, 686–687, doi:10.1038/ngeo1584

Parks, MM et al., 2012, Evolution of Santorini volcano dominated by episodic and rapid fluxes of melt from depth. Nature Geoscience 5, 749–754, doi:10.1038/ngeo1562

 

Air photo of the northern part of Nea Kameni, the youngest of the volcanic islands of Santorini. Taken in May 2012 by the NERC Airborne Research and Survey team.

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