One of the highlights of the EUROVOLC summer school was undoubtedly the day-long fieldtrip on Mt Etna, visiting the North-East rift zone with our expert guide Stefano Branca, who has spent many years mapping the eruptive deposits of the volcano. An early 8.30 am start was required to make it to the small town of Piano Provenzana, over 2000 m above sea level, where the trail began. On arrival, the impacts of Etna’s eruptions were immediately noticeable, with the road leading to the town built on top of the wide lava flow of the 2002-03 eruptions. It turns out that this event was particularly bad for the population of Piano Provenzana, which was mostly destroyed and buried by flowing lava (see below).

As we began climbing up towards the rift, we noticed some small ash plumes rising from the summit. However, we were reliably informed by our guides that these were caused by collapse of sections of the north-east crater rather than new magma reaching the surface. After clambering across the rubbly surface of the 2002 flows, we reached some deep holes and a line of cone shaped structures. Stefano informed us that the holes were in fact eruptive vents from 1914, where dykes propagated along the NE rift and fed fissure eruptions along its length. These built up the cones by continuously erupting small, bubble rich fragments of magma (scoria) and larger lava bombs.

We then moved on towards the much larger Monte Nero scoria cone, formed during the famous eruptions of 1669, where lava reached the major nearby city of Catania, causing serious damage. On the flanks of the scoria cone, extremely large, metre sized lava bombs were found by the path, indicating just how powerful this eruption was. Unfortunately at this point the weather took a turn for the worse, forcing us to retreat to a bar in Piano Provenzana.

After a long lunch, the weather improved and we headed to a multi-parametric monitoring station, to see the equipment we had been learning about all week. The stations are built into the ground, contain both seismometers and GPS units, and are powered by solar panels. These instruments continuously transmit data to the INGV observatory in Catania to allow real-time monitoring of the volcano.

Our final stop of the day was the Pernicana fault, which extends from the NE flank of Mt Etna to the coast. Earthquakes and large, up to metre scale movements are common on the fault, which is helping to facilitate the slow sliding of Etna’s east flank towards the sea. In the field, the fault is marked simply by a ditch next to a steep rock face, which exposes lavas from prehistoric eruptions of Etna uplifted by several slip events.

Soon I’ll be covering the final days of the summer school, as well as adventures from my second visit to the Caribbean!

The first week of September was spent on yet another excursion, this time to the EUROVOLC Summer School on Mt Etna, focussed on “Understanding sub-surface volcanic processes”. EUROVOLC (The European Network of Observatories and Research Infrastructures for Volcanology) aims to promote interaction between volcano researchers and observatories across Europe, and part of its role is to provide training workshops for PhD and postdoctorate level researchers to learn about volcano monitoring.

Things kicked off with an icebreaker meal at our hotel in the sleepy town of Linguaglossa on the NE slopes of Etna, where I was introduced to the 30 or so fellow attendees. Almost all were PhD students and postdocs from across the world, with a huge range of interests from volcano ground deformation to landslides on the flanks of volcanic edifices. The first morning of the workshop focused on understanding seismicity related to volcanoes, including how to interpret different types of seismic signals produced by moving magma (see below).

For anyone interested, real time seismic data from Etna and Stromboli volcanoes can be accessed online here: http://www.ct.ingv.it/en/real-time-seismic-signal.html

After feasting on a three-course lunch (which we soon learned was to become the norm) we headed outside for a demonstration of seismic and infrasonic (sound wave) monitoring equipment, which ended up being filmed by a local news network for TV!

The second day involved an introduction to more monitoring techniques, such as measuring tilt of the ground, strain (change in volume due to stress) and changes in gravity. Shortly before lava fountaining episodes at Etna, tilt and strain start to decrease due to deflation, as the magma leaves a deeper reservoir and erupts. A negative gravity anomaly also accompanies these changes, due to the accumulation of gases/foam in the conduit feeding the eruption – the negative anomaly occurs because gases have a lower density than the rising magma and surrounding solid rock.

In the afternoon we got to have a go at setting up the gravimeter and making some measurements, before rounding off the day with lessons about what the crystals and chemistry of Etna’s lavas can tell us about its eruptive behaviour.

More updates on the EUROVOLC Summer School coming soon, including the Etna fieldtrip!

Its been a long hiatus from blogging, mainly due to spending a lot of time in the lab obtaining the first dataset of my PhD, and then attending my first international conference, the subject of this post.

The conference in question is Goldschmidt, which specialises in geochemistry and attracts geochemists from all over the world annually. This year, it was hosted down by the beach in sunny Barcelona, and attended by over 4000 delegates.

My primary reason for attending was to present a poster on my initial PhD work, to discuss the data with other geochemists and obtain feedback. Attending such an event also provided opportunities for networking and attending talks on a huge range of topics.

On the first morning, I collected my name badge along with a thick booklet listing everything going on during the week and made my way to the first talk. Several sessions focusing on different subjects were running parallel, but thankfully the conference organisers released a handy app which allowed me to pre-plan the talks I wanted to attend. I spent the day hopping between presentations on everything from crystal chemistry to chemical signals of a newly forming undersea volcano, learning a huge amount in the process. Come the evening, it was time to attend the poster session, a chilled out affair of scientific discussion fuelled by plenty of free booze!

The following few days followed much the same pattern, also involving plenary talks (presented by renowned researchers on broad topics such as the beginning of plate tectonics) and discussions with collaborators over lunch. I was able to catch up with Ola Zawalna-Geer, a postdoctoral researcher at Exeter studying Sakurajima volcano in Japan (below), which I worked on during my MSci degree. Having discovered that our datasets compliment each other very well, we are now working on coming up with a detailed model for the magmatic system below the volcano.

My poster presentation on the Wednesday evening was a busy couple of hours, with the poster attracting a constant stream of interested academics and fellow PhD students. The discussions and points raised proved extremely useful, and made me realise that my findings so far are rather exciting!

Overall, it was a fantastic experience to attend a major international conference, and despite the size of the event, it was very relaxed and welcoming for first-timers. I’d definitely encourage any PhD students at an early stage to attend such an event, as the opportunity to get so many expert opinions on my work and network with other researchers has definitely given me a lot of ideas and confidence for the rest of the PhD!

 

 

Following my adventures in Tenerife, I took the opportunity to continue teaching about volcanoes at the Schools Science Festival, run at Durham University on 2^nd-4^th April. Along with several colleagues from the department, I helped to run practical sessions for year 9 and 10 pupils entitled “How to survive a volcanic eruption”.

We initially asked the pupils to think about what comes out of volcanoes and showed them some interesting examples of volcanic rocks, before starting them on their experiments. We challenged them with investigating how slope angle and viscosity affect the speed of a “lava flow”.

Of course, no real lava was available, so we simulated it with golden syrup, mixed with varying amounts of water to represent different viscosities. Each group was given a different viscosity “lava”, which they then poured down slopes set at different angles. A lot of the students observed that our “lava” travelled rather slowly – this is in fact realistic and shows that in reality, it is possible to outrun (or maybe even outwalk) a lava flow. The groups then plotted their results on our interactive chart, making the key observations that more viscous lava flows more slowly, and that steeper slopes lead to faster flows.

To give their findings a real world context, we then introduced the students to Ascension Island, a volcanic island in the Atlantic currently being worked on by masters students Annabelle Foster and Rebecca Winstanley. We asked the different groups to use what they had learned to draw on a map of the island where they would predict to be hit by lava flows during an eruption. Many sensibly predicted that the lava would travel down the steepest slopes, while some made the point that a larger eruption could in fact cover most of the island!

We then tested their ideas on our 3D cardboard model of Ascension, pouring syrup on the “erupting vent” and watching to see whether the lava would hit the position of the towns on the island. Each experiment produced different results, with some destroying two towns, and others destroying none. This ended up a rather realistic demonstration of the unpredictability of volcanic eruptions!

Overall our experiments were a great success and the sessions were enjoyed by pupils and event staff alike! On a personal note, I greatly enjoyed leading some of the sessions and I’m hoping to do more teaching and outreach, and inspire more people to study volcanoes in the near future.

We woke up on day 5 to torrential rain and reports of snow up in the caldera and on Teide! Since the day was supposed to be spent in river valleys liable to flooding, we abandoned the field for the morning (much to the delight of the students). After lunch, the weather cleared out a little, and we headed off to a backup locality near the town of Guimar with a large exposure of the Poris ignimbrite, erupted at 273 ka from the Las Canadas stratovolcano. This showed a range of depositional features including ash fall, massive ignimbrite with tree casts, cross stratified ignimbrite and a lithic rich upper layer, all topped by a paleosol. This sequence can be interpreted as 1: initial fallout from a Plinian eruption column. 2: Collapse of the eruption column produces pyroclastic density currents, which rip up trees on the slopes of the volcano and carry them seaward. 3: As the current wanes and becomes more dilute, cross stratified deposits form. 4: Possible caldera collapse ejects lithics in a final, clast-rich pyroclastic density current. 5: A hiatus between eruptive products reaching this location allows a palaeosol (soil horizon) to develop.

Later in the afternoon, we took the students to the coastal exposures of San Miguel de Tajao, which show a fantastic sequence through several Plinian eruptions from the Las Canadas stratovolcano. The students were given time to analyse and log the deposits before coming to an interpretation as to how many eruptions were represented. The outcrops here provide a particularly good example of how topography affects deposition from a pyroclastic flow – some units appear in topographic lows in one section of the exposure yet are not found 20 metres away where a topographic high existed at the time of deposition. Another explanation for any “missing” units in the sequence is that they simply flowed further into the sea, or have been completely eroded away by a subsequent pyroclastic density current.

The final day saw the students completing their independent assessment at Caldera del Rey, a maar volcano (produced by phreatomagmatic eruptions, similar to Montana Pelada from day 3) in the south of the island. Following this, we organized an evening quiz by the hotel pool, where the demonstrating team successfully fooled the students in the “secrets of the staff” round, and “Ignim-not-so-brite” won the award for best team name.

 

 

 

Day 4 provided the highlight of the trip for many – a walk around the towering spires of the Roques de Garcia formation in the spectacular barren landscape of the Las Canadas caldera. We kicked things off by asking the students to sketch the lower part of the Roques de Garcia, including the bizarre looking stump with many colourful rock layers. This prompted an interesting discussion about the origin of these deposits – a favourable interpretation is that they were formed in a lake that temporarily filled the caldera in the past. There were also some breccia deposits with large blocks up to a metre across, thought to be formed by collapse events on the old caldera walls.

A wander round to the back of the Roques de Garcia provided perfect views of Teide and the lava flow deposits snaking down from the edifice. The magmas erupted from Teide are unusual in that they are highly alkaline, meaning that they are lower in silica and enriched in sodium and potassium relative to most magmas. This gives them an unusual mineral composition, dominated by large white sanidine (K-feldspar) crystals, along with some kaersutite (Ti-amphibole). The students then had the opportunity to study the unusual morphology of the lavas, which have odd looking lobes and ropy pahoehoe sections.

We finished the day by discussing the process of caldera formation, and how recently models have changed from the idea of a “bung” collapsing into a central magma chamber which is emptied, to frequent episodes of partial collapse due to the emptying of multiple smaller magma reservoirs within a connected “crystal mush” system. The present day Las Canadas caldera is made up of three “nested calderas” which get progressively younger in a north-easterly direction. However, the origin of these “calderas” is controversial, with some authors claiming that they represent the headwall scarps of massive landslides that ended up in the ocean to the north. This led to some in depth discussions with the students as to how they would go about determining which theory was correct, or whether both processes could be operating. Personally, I feel that the voluminous ignimbrite deposits in the south of the island, which record multiple Plinian eruptions, provide strong evidence for caldera collapse. However, it is possible that such events may have triggered, or have been partially caused by, landslides.

Day 3 started with a trip to the coast to view the Montana Pelada tuff ring, a volcanic feature formed by the interactions between magma and water. A long climb up and over the steep circular outer wall led to an initially confusing exposure with layered pyroclastic deposits dipping in opposite directions. The students began by sketching the outcrops and identified 3 main units within the sequence – the lowermost lithic rich unit dipping towards the sea, a thinly bedded unit dipping in the opposite direction and a lithic poor upper unit with an erosional base.

After this exercise, we discussed what may have produced the characteristics of the different units and how this relates to magma-water interactions. The lower seaward dipping layers were interpreted to be produced by initial explosions where the water-magma ratio was high, which ripped apart the underlying basalt. This meant that the resultant pyroclastic density currents were rich in basaltic lithics.   The thinly bedded inward dipping layers showed cross bedding and bomb sags (where a lava bomb creates a depression as it lands in the flow deposit), suggesting that they were deposited by drier, more dilute currents as the magma-water ratio decreased. The uppermost lithic poor layer represents a later eruption where the magma had a much lower water content, producing a typical ignimbrite deposit. The yellow matrix colour of some of the rocks at Montana Pelada is due to the presence of palagonite (hydrated basaltic glass) which shows that these rocks underwent hydrothermal alteration (a change in chemical composition due to interaction with hot water) after eruption.

After a lunch stop by the sea that involved getting continually sandblasted, we moved inland to continue the explosive theme at a roadcut through the deposits of the approximately 600 ka Granadilla eruption. This eruption was produced by the central Las Canadas volcanic edifice on Tenerife, which formed between the shield volcanoes after 3.3 Ma. The Granadilla deposits start with a lower layer of angular white pumice containing some perfectly preserved bubble walls, and a lithic rich, massive upper layer. The students quickly concluded that the well sorted pumice layer was produced by fallout from a Plinian eruption column, with the massive unit above it the product of a subsequent pyroclastic density current (PDC) after collapse of the column.

The teaching and demonstrating team spent the evening providing feedback on the students’ summary sketches for the previous day. Having not been involved in the marking of student work before, I found this a useful exercise in learning how to give helpful feedback that they could then work on during the remaining field days. In the evening we enjoyed a trip to the local carnival, where we came away with a fluffy T-Rex for the department! Follow his adventures on the department Twitter feed: @DurUniEarthSci.

Day 2 was spent at Masca, in the northwestern corner of Tenerife. The sheer cliff exposures here cut through the remnants of an old shield volcano, the Teno massif. The island of Tenerife has been through several stages of volcanism, beginning with a shield building phase, which produced the Roque del Conde (south), Teno (north-west) and Anaga (north-east) massifs. This was then followed by construction of the Las Canadas stratovolcano in the centre of the island between the three shield volcanoes. The Las Canadas edifice has since been through several episodes of caldera collapse and the current caldera is home to the Teide-Pico Viejo volcanic edifice.

The Teno shield volcano section at Masca revealed many layers of lavas, scoria cones and columnar jointed sills, all cross cut by thousands of dykes. The students were tasked with analysing these dykes by looking at their geometry and composition, before presenting their findings to the group. Those looking at the compositions uncovered two different types – crystal rich, forsterite (Mg-olivine) and Ti-augite (clinopyroxene) bearing ankaramite dykes, and mostly aphyric basaltic dykes. Many of the dykes have obvious chilled margins where they contact the baked country rock.

The groups studying dyke geometry concluded that most of the dykes showed a similar orientation. This orientation was not radial from the central Teide-Pico Viejo edifice, as may be expected, which led them to the interpretation that these dykes may instead be radiating from what was the centre of the shield volcano. Some unusual “handshake structures” were found, where the interacting stress fields at the tips of propagating dykes have caused them to curve inwards towards each other (see below).

After lunch and some ice cream, we took a relaxing boat trip along the coast at Los Gigantes, to view the base of the shield volcano. This allowed close-up observation of the layered lavas, sills, scoria cones and dykes, along with some friendly local dolphins! This exposure demonstrated perfectly how a shield volcano is built by repeated eruptive events and intrusions.

Cliff section seen from the boat, showing the different components of the Teno shield volcano.

References: Hernández, P.A., Padilla, G., Barrancos, J. et al. Bull Volcanol (2017) 79: 30. https://doi.org/10.1007/s00445-017-1109-9

 

 

Over the course of the last week, I’ve been working as a demonstrator on the Durham University 3rd year volcanology fieldtrip to Tenerife, so I figured I’d talk a bit about what we did and the geology of the island here. After a smooth flight from Newcastle and a relaxing first evening at our base in Los Cristianos, we began the first field day with a visit to El Chinyero scoria cone, the site of the most recent eruption on Tenerife in 1909.

We first asked the students to analyze the material they were sitting on – shards of glassy, vesiculated mafic scoria. We then pointed out the presence of lava bombs on the slopes of the cone, and discussed the difference between deposition of clasts as fallout (scoria)and ballistics (bombs). To demonstrate ballistics, we had the students throwing lava bombs and pine cones to represent ejecta of different shapes and densities, to show how these factors affect how the ballistics are distributed around the volcanic vent. Unsurprisingly, the students could only throw the dense angular bombs a short distance, with rounded pine cones and more aerodynamic, lighter bombs travelling further.

We then slogged our way up the steep side of the cone to get a better view of the edifice and determine the location of the vent. The view from above also revealed lava flow deposits from the eruption, which the students spent time getting to grips with in the afternoon. Some of their observations included rippled surfaces and sheared near surface bubbles in the lower flow units, and rubbly broken up surfaces in the upper flow units. These were interpreted as being produced by pahoehoe and A’a type flows respectively (shown below).

After a long day in the field, the teaching team gave some brief feedback on students notebooks in the evening, before heading to a local BBQ restaurant to consume vast quantities of steak (to set us up for the next day)!

 

With all the rocks collected and catalogued, we loaded 68 kilos of them into the hire car and made our way down to the shipping company in Kingstown. Traffic was particularly bad and meant the short journey took over half an hour, though this did give us the opportunity to enjoy a Caribbean chat show on the radio. Once at the shipping company, the process was sorted smoothly, and we found our work done by 11 in the morning!

We decided to treat Kemron and his colleagues to lunch in return for their help, which led us to the “treehouse bar” built entirely of wood, where we enjoyed some tasty stewed fish. We spent the afternoon exploring some of the beaches on the leeward side of the island, including the warm seas at Buccament Bay. After struggling our way back through the Kingstown traffic, we celebrated the trip success with several glasses of the excellent Captain Bligh rum from St Vincent.

The next morning, I headed off for a few days holiday in Barbados, while George moved on to Trinidad to organize the VoiLa meeting that will be held there in September. This meeting will bring together all the collaborators involved in VoiLa, from UK and European universities and our West Indian partners such as UWI Seismic. I’m hoping that by the time September rolls around I’ll have some exciting data to present out there from the samples collected on this trip!

The field-based blogging will continue next week, as I am lucky enough to be demonstrating on the Durham University volcanology field course to Tenerife, where I’ll be showing some very different volcanic landscapes.