The mystery of oozing, fluidal obsidian pyroclasts co-erupting with scoria from a basaltic fissure-eruption, Ascension Island, South Atlantic.
Basaltic eruptions are the most common manifestations of volcanism on Earth. Pyroclasts help volcanologists unravel the timeline of magma storage and ascent prior to eruptions and vent processes during eruptions, which in turn contributes to hazard mitigation models associated with impending volcanic eruptions.
A recent field excursion to Ascension Island uncovered unique and highly unusual obsidian pyroclasts which co-erupted with scoria in a dominantly basaltic fissure eruption. They comprise of dense glassy bombs which range in size from millimeter spherical beads to large spatter-like bombs (>40 cm in diameter). The obsidian clasts show fluidal shapes (such as suspended drops, large outflows and stretched filaments) which imply that they erupted with unusually low melt viscosities and landed hot on chilled scoria clasts.
Figure 1: Photographs (taken by Rich Brown) of the obsidian pyroclasts found within scoria ramparts. (A) Tongue-like pyroclast that flowed on impact. (B) Broken glass filaments with thin glass bridging between them. (C) Larger glassy pyroclast that has undergone considerable post-impact flow. (D) Glass droplet frozen onto the side of a scoria clast on the fissure edge.Figure 2: Photographs of the obsidian pyroclasts. (A) Example of the base of a typical pyroclast which contains scoria and lithic clasts. (B) Cut section showing how the glass has flowed internally and interacted with the scoria as it landed. (C) Cuboid glassy clast with near parallel sides (shaped like a chocolate – but again not edible!). (D) Spherical glass drop stuck to the exterior of the scoria clast. (E) A smaller feature of photograph A; delicate thin filaments bridging a narrow crack in the exterior of the sample. (F) Bubbles in the glass which follow the edge of scoria clasts.
In-situ geochemical analyses on the obsidian and scoria glass (using electron microprobe) confirms two distinct magmas; the obsidian is rhyolitic, while the scoria is dominantly trachy-andesite. The magmatic compositions are bimodal, with clear separation between the obsidian and scoria components which is exemplified in differing macrocryst species present in the two pyroclasts.
Figure 3a: Total alkali vs. Silica plot showing two distinct compositions of the obsidian (rhyolite) and scoria (dominantly trachy-andesite). Figure 3b: Ternary feldspar compositional plot of obsidian and scoria macrocrysts.
The obsidian clasts only account for a small-volume of the total ejected material. This, coupled with the distinct magmatic compositions, suggests that the two magmas did not reside together in a density stratified magma chamber. An alternative possibility is that a shallow pocket of degassed rhyolitic magma was intersected by ascending mafic magma in dike. However, this also does not account for the low volume of eruption obsidian and absence of mixing/mingling textures. This is comparable in the wider Ascension Island magmatic suite where there is no evidence for magma mixing. Therefore, the storage of the two magmas and fragmentation at the subsurface remains ambiguous.
Figure 4: Schematic diagram of fissure (red) through felsic lavas (yellow) on Ascension Island. At t1, surrounding country rock (felsic lavas) are ripped from the conduit margins. They are entrained within the fire fountain at t2, and by t3 have likely outgassed, losing the majority of exsolved volatiles. On deposition (t4) the magma remained hot and flowed through pore spaces within the underlying scoria.
Currently, the preferred hypothesis for their origin is assimilation of water-/gas-poor felsic country rock, which bypassed the mafic eruption and remained in isolation until deposition. Reheating to the basaltic temperatures of the mafic dike would exceed the glass-transition temperature, remobilising the clasts, thus invoking highly fluidal textures. However, similar pyroclasts elsewhere that co-erupted with basalt have examples of large rhyolitic inclusions which show no evidence of re-melting. Ascension lacks any intermediate clast-type, which highlights the unusual nature of these pyroclasts.
The origin of these obsidian pyroclasts would benefit from future field excursions to Ascension Island, to look closely at the visible conduit and potentially uncover more pyroclasts which show a range in melting regimes. Additionally, obtaining water contents in the obsidian would provide insights into the magmatic processes (melting, crystallisation and assimilation), further placing constrains on their genesis.
Special thanks to Rich Brown, Katy Chamberlain, Fabian Wadsworth and Kate Dobson for insightful conversations and help during the supervision of this project.
Annabelle Foster (annabelle.foster@durham.ac.uk) is in the first year of her doctoral studies at Durham University (United Kingdom), after completing a masters by research. Currently, Annabelle looks at obsidian textures, stable isotopes and uses major element geochemistry to reconstruct the range of physical processes controlling degassing at silicic volcanoes. The project is supervised by Fabian Wadsworth, Madeleine Humphreys (Durham University), Dan Barfod (Glasgow, SUERC) and Hugh Tuffen (Lancaster University).
Annabelle also runs an Instagram geology blog (@Geology-talk) where she shares bite-sized pieces of geology, geo-art and her ongoing research. You can follow her on twitter too (@Volcannabelle)!
Welcome VIPS followers! Since our last post, the world seems to have turned upside down. We hope everyone is staying in good health and spirits, and doing what they can to minimize the spread of the COVID-19 virus. In the meantime, why not spend that extra time at home reading through our interview with Dr. Michael John Heap, material science extraordinaire! He’s currently a researcher and lecturer at University of Strasbourg, France, working in the Rock Deformation Laboratory (LDR) (on twitter @LDR_Strasbourg). We sat down with him last August (2019) while on a two-week field trip in Iceland. Enjoy!
VIPS Team
Hello and welcome! We’re in a rented apartment in Höfn, Iceland, with Dr. Michael Heap. Could you give a short self introduction?
Mike Heap
My name is Michael John Heap. I am a lecturer, assistant professor, at University of Strasbourg in France. Principally, my training is in geology. I have an MSc in geology from the University of Liverpool. My PhD was in experimental rock deformation at University College London. I spent a lot of my time deforming sandstones. Following a postdoc at LMU Munich, I started, alongside some great colleagues, to use these methods and our understanding of porous sedimentary rocks to try to better understand volcanic rocks. And this is what I’ve been doing for the last 10 years. I don’t know whether I, or others, would classify myself strictly as a volcanologist… I’m more of someone who’s very interested in measuring things that could be useful for certain people, so I tend to flitter around. But yeah, I measure things.
VIPS
Okay. So let’s start easy. What is your favorite volcano, and why?
MH
I think my favorite volcano is Whakaari in New Zealand. It’s one of the volcanoes I’ve studied with many different collaborators and friends. It’s a really spectacular place. It’s about 40 kilometers off the north coast of the North Island of New Zealand, and you have to take a boat or a helicopter to get there. There’s no walking: you take a one-and-a-half-hour boat ride and you’re basically where the action is. It’s spectacular. There’s always something going on. It also smells really bad. [This interview was conducted before the tragic event on December 9, 2019 in which more than twenty people lost their lives.]
VIPS
Okay. That’s awesome for a volcano. So, currently where lies your main interest in research?
MH
My current research focus is the influence of hydrothermal alteration on the physical properties of volcanic rocks. A lot of volcanic systems have an associated hydrothermal system, and this is modifying or altering the rocks. I explore what such alteration does to the physical properties, such as strength and permeability, of volcanic rocks. Understanding what this process does to the rocks is important because if the strength and permeability of these rocks is modified, it could influence flank stability, which has all sorts of hazardous knock on effects, and whether the volcano erupts effusively or explosively. Anyway, the impact of alteration on the physical properties of volcanic rock is what I’m focusing the next years of my research on.
VIPS
What are your favorite aspects of your research?
MH
A lot of the lab stuff we do is quite laborious, I guess it’s in the definition. It’s quite routine, in a way. And so what I like is after you’ve made a lot of these measurements—be it porosity, strength, or permeability—and you finally click on the figure, and this is like a big reveal. And either it works or it doesn’t!
VIPS
So you like to see the trend?
MH
Yeah, or not! So I think in lab work (because I don’t do so much fieldwork) there’s some satisfaction in creating a big data set and testing a hypothesis. When you plot those two variables against each other, and you press go! I think somehow this can be satisfying.
VIPS
How would you define your role as a scientist in society?
MH
Well, for me at least, it took some practice and some lengthy reflection time. I needed to speak to a lot of different people to understand where my place was in science, where I could help, and what I could do. If we make laboratory measurements, or we make field observations, then we can hope that someone is going to use that information. And then hope that, eventually, someone in society—the average person that may not know anything about volcanology—would benefit. Reaching out to communities with information is not easy, not for me at least, and requires a certain character and certain amount of training. I have amazing respect for scientists who do this type of work. Personally, I would like to think that what we do in the lab is going to affect or help certain communities. I’ve tried more and more to work with people involved in these activities. For example, very recently I have worked with the volcano observatory in Guadeloupe. And that’s super rewarding. I feel like, the information that we can glean in the lab, be it big or small, will help the person tasked with relaying information to those living on the flanks of the volcano in a time of crisis. But when I think “have I been in a position where I could confidently say that I helped someone?”, I’m not sure. I think that’s a really difficult question. I’m not sure I’m answering your question…
VIPS
Okay, so you were saying that it is the most rewarding to basically be able to help people? Would you also say that this your accomplishment in your career, what you’re most proud of? Or something else?
MH
Another difficult question… I don’t know what I’m most proud of. In terms of societal impact, I think a lot of other people have done a lot more. My favorite thing about science is collaboration: talking to different people from different backgrounds, different communities, different cultures. That’s not necessarily what I’m most proud of, but I think this is what interests me the most. And if people benefit from that, or gain some insight from that, and then I’ll be very happy. That would make me proud.
VIPS
And what was your motivation to start down the academic train? And did you always see yourself in academia?
MH
I guess it was my third year at university as an undergrad when I asked the questions “how do I do a PhD? And what does that entail?” And I think that was the moment when I really started to enjoy geology, and I just wanted to do more. And then the rest of it kind of fell into place. That’s not really helpful advice! I applied for PhDs and accepted an offer from University College London. Then afterwards to Munich, and then onto Strasbourg. I still feel motivated about finding new things out. I think that these two weeks of fieldwork [in Iceland] is a collection of people who are super interested in exploring new things and finding out new stuff.
VIPS
What are the best things about the academic workplace? What gives you motivation and drive?
MH
A large part of my motivation, and this might sound a bit cliché, is working with friends to solve problems. Seeing students super excited about things that you’re excited about. It’s always very encouraging and motivating when you find someone who is like-minded and super keen. And maybe that’s because of something you said, or something you said in a lecture or practical class.
VIPS
What advice would you give to an early career researcher?
MH
I’ve given different advice to different people in different stages of their early career. I think that it’s good to be bold, it’s good to ask questions. If you really want to work with someone, for example, then I find that a lot of scientists, despite how senior or busy you might think they are, respond very well to well-worded emails or conversations at conferences. But I know that this type of advice will not necessarily suit everyone. So I think people can tackle this in their own kind of way. But I would definitely recommend trying to be as bold as you can within your comfort. And then see where it takes you.
VIPS
Cool. Our last question: given the talk of mental health and academia, especially on Twitter, how do you maintain a healthy work/life balance? How do you encourage your students to do the same?
MH
To be very honest, I’m not sure that I have a great work/life balance. I feel like it’s somehow very often difficult to switch off, which I can see is detrimental. You’re trying to enjoy being away somewhere and you’re thinking about some email to some co-author that you’re letting down because you haven’t emailed them. But I would definitely encourage people not to go down the same route. So for example, my current PhD student, Lucille, is very musical. So together with Patrick, whose is co-supervising her project, we’ve encouraged her to keep continuing to play music, to go to concerts, and to record her music because I think that, ultimately, a happy PhD student is a good one. But also I think that’s really good for her well being to keep continuing to do that. But then, personally, I think I could do a little better. I don’t know what the answer to that is.
Academic publishing is in crisis. We are all familiar with the problem: publishers require that we pay in order to read published research in their journals (per article, or by subscription). Alternatively, if they do make it freely accessible online (open access), then they instead charge a fee to the researchers who carried out the work and wrote the papers in the first place (usually via research grant funding). Therefore, the costs involved in reading or publishing work fall to either the audience or the researchers, and they are high.
A typical workflow might be: researchers work to get funding to do research, they conduct the research, then they write their results into academic papers, and submit those to journals to be reviewed, edited, and, hopefully, published. When someone from outside the academic community hears that members selected from the same research community do the editorial work and the reviewing for journals, they might be justified in asking what it is that the journal publishers themselves do? Why is it, they might ask, that the researchers do almost all of the work involved in creating published articles, and curate the process so that the results can be trusted, but then are often also the ones who bear the burden of cost for the product? The answer to this dilemma is complex, but the headline reason given is often that publishers have high costs to deal with. This is true – reliable and large-scale publishing can be expensive. But the truth is that they also turn incredibly high profits[1].
At Volcanica, we strived to test the claim that publishing journal articles simply could not be done without someone (researchers or audiences) paying for it. In response to the state of affairs, we have succeeded in creating a journal that is free for everyone, from beginning to end, and we are the only option of this type for volcanology research. How are we able to do that? First, we rely on a growing enthusiastic body of editors, reviewers, typesetters, and proof-readers, all of whom are working for free through this shared vision of an alternative publishing model. Second, we receive a small (€500 p/a) grant from the Strasbourg University Press, which covers the few costs involved in publishing academic research[2].
Since our launch in November 2017, we have published 2 complete issues in our first complete volume, comprising 7 Research Articles, 1 Report, and 2 Editorials, and we are currently publishing the next issue (5 articles and counting), set to be complete in July 2019! With the help of a large group of volcanologists worldwide, we are growing quickly, and we like to think that this growth is a testament to the value inherent in sharing our work for free. We are interested in pushing the boundaries of what is possible with publishing, so if you have a creative idea, we are keen to hear from you!
We hope that the VIPS community will consider Volcanica as the free and open option for the latest in volcano research, and we look forward to hearing from you here: https://www.jvolcanica.org/
[1] Larivière V, Haustein S, Mongeon P (2015) The Oligopoly of Academic Publishers in the Digital Era. PLoS ONE 10(6): e0127502. doi:10.1371/journal.pone.0127502
The dark heights of Karls Spur’s basaltic lava flows on the left and the brownish colored rocks of the felsic Reyðará-Pluton on the right.
Hello fellow VIPS enthusiasts,
Greetings from Iceland! The VIPS-team is currently in Iceland on field work, hence the delayed update this week. Many of you know field work has little spare time, so the full story about our adventures and misadventures will follow as soon as we are back in the office. We hope you stay tuned!
That said, if you are an early career researcher and want to share your field adventures, lab-stories or other encounters get in contact with us at vipscommission@gmail.com!
Happy summer!
VIPS-team
Tobias, Emma and Taylor taking a break among the scree.
Hi volcanophiles and all you interested blog followers! This week we have an announcement for the sixth LASI conference taking place in Malargüe, Argentina during 25-29 November 2019. LASI stands for “Laccoliths, sills and dykes: the physical geology of subvolcanic systems.” This year’s invited speakers are:
Alan Bischoff (University of Canterbury, New Zealand)
Janine Kavanagh (University of Liverpool, UK)
Nora Rubinstein (University of Buenos Aires, Argentina)
Freysteinn Sigmundsson (University of Reykjavik, Iceland)
Register now and hear their talks regarding seismic imaging, lab modeling, and field studies of volcanic plumbing systems. Additionally, there will be a wide variety of other topics given by many international scientists presenting in oral and poster sessions. In the evenings, socialize and discuss the day with your colleagues while enjoying delicious Argentinian food and drink in the town nestled in the foothills of the majestic Andes mountains!
An essential part of each LASI conference is its incredible guided field trip. When was the last time you stood at the same outcrop with specialists in volcanology, tectonics, structural geology, petrology, geochemistry, geochronology, geophysics, exploration geology and modelers? This year’s trip will be across the north Nequén Basin, south Mendoza province, where there are spectacular exposures of rhyolitic laccoliths and an andesite sill complex. Make sure to sign up while there are still spots left!
Curious? Check out their webpage for more information: https://lasi6.org/.
Abstract submission deadline is 1 July!
Outcrop in the Nequén basin of andesite sills emplaced in organic-rich sedimentary rocks (photograph by Dougal Jerram, taken from lasi6.org)
We are Tobias, Taylor and Emma – the new moderators for the blog “Focus on VIPS”, the official blog for the IAVCEI commission on Volcano and Igneous Plumbing Systems. We got some exciting new things coming up the conduit for the next weeks so stay tuned!
We want you to contribute to our blog!
Did you just come back from amazing field work? What are the methods you use in your lab/group? Did you just publish a new paper? Get in touch with us and contribute to our blog about what’s going on in the field of VIPS. We are aiming to make a new post fortnightly.
We highly encourage early career researchers (ECRs) to contribute to our blog, and let others know what you are doing and to get new ideas on what could be done in future through collaborations. That said, we also hope to attract some of the more experienced researchers in the field to tell us a little about their academic work and careers to inspire ECRs to try new methods or ways. We have a blog-style post format for ECRs and an interview format for the more experienced researchers.
Tobias Schmiedel is currently a Postdoc at Uppsala University, working on magma properties and their effect on the geometry of dykes. He did his Masters in Mineralogy at the Technical University Bergakademie Freiberg (Germany). During his PhD at the University of Oslo, Tobias used laboratory experiments and 3D seismic interpretation to investigate the influence of host rock strengths on the emplacement and geometry of horizontal magmatic intrusions, i.e. sills, cone-sheets and dykes. Tobias likes hosting dinner parties and collecting gin. He is also an expert in dabbling with things in the lab and getting old machines back up and running.
Emma Rhodes is currently a PhD Student at Uppsala University and part of the Centre of Natural Hazards and Disaster Science (www.cnds.se), working on deciphering the Reyðarátindur Pluton in Iceland. She also works on hazard communication. Emma did her Masters at the University of Canterbury, New Zealand on extrusive dome features at Santiaguito, Guatemala. Emma likes rock climbing and has taken to the Swedish pass times of cross-country skiing and skating. She likes attending Tobias’ dinner parties.
Taylor Witcher just started as a PhD student at Uppsala University in May. Her project focuses on the structural geology of magma as it moves through the upper crust, and she is analyzing the resulting fracture networks in an ancient magma chamber exposed in eastern Iceland. Taylor got her Masters degree at Ludwig-Maximilian University in Munich, Germany, where she studied the viscoelastic properties of silicate melts in the laboratory as an analogue to conduit processes during volcanic eruptions. Taylor likes to paint, accumulate houseplants, and jump in any large body of water she encounters.
By Nicolas Le Corvec, Observatoire de Physique du Globe de Clermont-Ferrand
Volcanic and Igneous Plumbing Systems – Understanding Magma Transport, Storage and Evolution in the Earth’s Crust is a new book released by Elsevier. Edited by Ass. Prof. Steffi Burchardt from Uppsala University and the Centre for Natural Hazards and Disaster Science (CNDS), this new book gathers an exciting interdisciplinary collection of topics. It covers a broad but complete physical, structural and petrological story about the mechanisms of magma transport within the crust, magma accumulation and evolution in storage zones, and magma ascent towards the surface, leading to the deformation and potential instabilities of volcanic edifices from a variety of geodynamical settings at the surface of the Earth.
The book, introduced by the editor S. Burchardt and divided into twelve sections, each of them written by the volcanic crème de la crème, is made to become an excellent reference for those like me who are interested in the broad concepts of magmato-volcano-tectonics. The storyline is neatly organized which helps the reader to immerse her/himself within the deepest part of the system and gradually rise with the magma towards the surface. Through our travel upward, we learn the different and fundamental aspects of magma propagation, from crustal to more primitive melts, i.e. from slow ductile deformation (Chap. 2 by Cruden and Weinderg) to the most effective transfer mechanism known as dyking (Chap. 3 by Kavanagh). The continuous emplacement of magmas within the crust’ subsurface leads to the formation of intricate networks of subterraneous magmatic sheets or swarms (Chap. 4 by Burchardt et al.) themselves forming complex volcanic systems at the surface of planets. The temporal development of such swarms is today an important matter of debate that inter-disciplinary studies are trying to resolve. Not all magmas reach the surface, intrusion to extrusion ratios span from 1/10 to 1/100, leading to a large accumulation of material within the crust. Chap. 5 by Galland et al. focuses on individual horizontal intrusions, known as sills, from which Morgan in Chap. 6 extrapolates towards the growth of large magma bodies. Both Chapters enable the reader to perceive the mechanical and structural complexity of continuously injecting new material within a solid medium and again how time is such an important factor controlling the evolution of these end-member systems. Magma bodies or reservoirs are literal melting pots within which chemistry is queen. Magma accumulation can occur at all levels within the lithosphere, thus more or less influencing the signature of the melts passing through or residing for longer periods. Jerram et al. beautifully managed in Chap. 8 to present physical, petrological and chemical concepts of what are probably the most secretive and recondite backrooms of the planet. The development and life cycle of these reservoirs in the crust’ subsurface allows for 1) the formation of complex edifices at the Earth’s surface, 2) generation of important crustal deformation and 3) giant catastrophic events. Built above these reservoirs, stratovolcanoes (of any chemical composition) are by essence unstable edifices as explained by Delcamp et al. in Chap. 9, that evolve through a succession of growth and failure phases greatly impacting the shallow and deep parts of the magmatic plumbing system. The reconnaissance of deformation patterns, however has allowed the scientific community to better depict the behaviour of VIPS and the propagation of magma with the crust’ subsurface. These signals and their interpretation are summarized by Sigmundsson and al. in Chapter 11 with a special emphasis on Iceland and its many incredible eruptions. The use of these signals have allowed to recognize the existence of gigantic magmatic structures that are the source for some of the largest eruptions on Earth. The complex existence of caldera volcanoes are portrayed theoretical and practically by Kennedy et al. in Chap. 10 using petrological, geophysical and geological data. Finally, each of these individual systems all belong to a larger global tectonic environment so specific to Earth, acting a bit like the background beat of a song on the generation, transport and eruption of magmas and the stability of volcanic complex. Chap. 7, by van Wyk de Vries father and son, describes the relationship between volcanism and tectonism within the main geodynamic environments but also show how the shallow tectonic, lithologic and topographic structures influence magmatism and volcanism.
This is only a very succinct and personal view of the total amount of information provided by the book. Overall, I very enjoyed the easiness of reading each chapter even not being an expert in all the topics. For me, the book principal strength resides in the excellent connection made between the theoretical aspects and the field examples, which is the essence of our work and an amazing reminder of the complexity of the systems we are studying. The book is also very well illustrated, figures properly fit the text and are nicely designed, without too much information that could obscure their message. While some sketches seem over-simplistic, I believe they also reflect our lack of our understanding on the geometries of VIPS.
The organisation of a book is always a difficult part, and chapters can always been moved endlessly to best match the content of each part. I feel that the chapters of the second part of the book are a bit isolated from the initial storyline depicting the upward propagation of magmas towards the surface. But the book isn’t written to be a novel, rather each section can be read independently without the need to look for previous information. Finally and that’s a personal point of view, I missed seeing a bit more references about planetary VIPS within the different chapters or as its own.
Nonetheless, I consider that this book by the quality and the plurality of its science on Volcanic and Igneous Plumbing Systems should be part of every lab’s library.
Nicolas Le Corvec is a postdoctoral researcher at the Observatoire de Physique du Globe de Clermont-Ferrand. His research focuses on the investigation of volcano-tectonic relationships in different type of volcanism, with a particular focus on analysing the interaction between magmatic activity and structural deformation. Nicolas uses a range of techniques, developing numerical and analogue models from fieldwork and remote sensing campaigns. To find out more about his exciting work read his recent Nature paper here: https://www.nature.com/articles/s41467-018-03865-x
Micro-earthquakes are often detected under and around volcanoes prior to an eruption, caused by melt movement at depth. Volcano seismology can therefore give valuable constraints of the plumbing system of a volcano. Studying the seismicity accompanying the 2014 Bárðarbuga-Holuhraun dyke intrusion, central Iceland, revealed a lateral intrusion that propagated episodically 48 km, over the course of two weeks before breaching the surface. The 6 months long eruption was fed from the subsiding Bárðarbunga caldera. The dense Cambridge seismic network provided an unprecedented insight into the rifting episode and associated caldera collapse, enabling accurate location-detection of over 40,000 earthquakes. The cumulative earthquake energy represents only 1% of the geodetic moment. This means that earthquakes can tell us where the magma is going, breaking it’s way through the crust, but not necessarily where it is flowing. Consequently, most of the magma flow was aseismic after a melt channel formed.
This unique data set enables investigating the earthquake source mechanisms, which are important to understand the dynamics of a rifting episode. In contrast to the conventional model we found the dyke earthquakes to be exclusively dyke parallel strike-slip faulting. The caldera earthquakes were found to be normal faulting parallel to the caldera rim, opposite to previous studies.
Thorbjorg Agustsdottir finished her PhD in volcano seismology from the University of Cambridge in December 2017, supervised by professor Robert S. White. She has just started working at Iceland GeoSurvey researching micro-earthquakes in geothermal areas. Follow Thorbjorg to find out more about her research and volcano love: @fencingtobba, and read her paper on the Bárðarbuga-Holuhraun dyke intrusion here: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2015GL067423
The 1783–1784 Laki Fires in southern Iceland were one of the largest and most destructive basaltic eruptions to have been witnessed first-hand. The eruption generated about 15 km3 of near-homogenous lava, blanketed Iceland and much of the North Atlantic region in a toxic haze and is implicated in the death of least a quarter Iceland’s population by famines. The eruption also took place over a period of eight months, orders of magnitude longer than most explosive eruptions. The length of fissure eruptions like the Laki Fires thus prompts questions about magma reservoir dynamics: was the magma assembled in a single event immediately before eruption or in a step-wise manner over many months?
By analysing the textures of rock samples collected throughout the eruption we found that the crystal proposals and crystal size distributions show that the efficiency of crystal entrainment varied greatly during the eruption. We also estimated that crystal residence times in the erupted melt were much shorter than the total eight-month duration of the eruption. The erupted magma was thus assembled incrementally, which has important implications understanding and monitoring the long-term behaviour of plumbing systems feeding basaltic fissure eruptions.
David Neave is a postdoc at the Leibniz Universität Hannover, Germany. His current research into magma mixing is funded by the German Research Foundation (DFG). He is primarily interested in combining observations from natural and experimental systems to understand how basaltic magmas are assembled and stored in the crust. You can read more about Laki here: https://doi.org/10.2138/am-2017-6015CCBY
By Kyriaki (Sandy) Drymoni, Royal Holloway University of London
Santorini volcano is a stratovolcano located in the Aegean Sea, which faced at least 4 caldera collapse events and sequences of Plinian and Intraplinian volcanic eruptions. This great volcanotectonic history exposed a dyke swarm of at least 91 dykes on the 5 km northern caldera wall on Santorini island. Systematic mapping of the dykes in conjunction with a study of their petrogenesis provide insights into the plumbing system and magma dynamics of Santorini volcano.
The dykes propagated through heterogeneous and anisotropic host rocks which affected their pathways: some dykes propagated straight through the stratigraphy but others were arrested or deflected. The combination of field geology with numerical modelling (COMSOL Multiphysics) constrains the parameters that control dyke propagation during emplacement in stratovolcanoes. Preliminary results show that layering, contacts, and local stresses largely control dyke pathways, encouraging either dyke arrest or propagation.
Kyriaki (Sandy) Drymoni is a PhD student at Royal Holloway University of London (Kyriaki.Drymoni.2015@live.rhul.ac.uk). She has completed extensive field campaigns at Santorini and Nisyros Aegean volcanoes thanks to a college scholarship (REID-RHUL) and the Kirsty Brown memorial award (RHUL) respectively. Her research focuses on producing numerical models on likely dyke paths for given loading conditions and magma/host rock properties. That is, to study the fate of dykes injected into the shallow crust, their likely paths and, thereby, the likelihood of dyke-fed volcanic eruptions. You can read more information on the Santorini dyke swarm in her paper: https://www.nature.com/articles/srep15785
Focus on VIPS 