Thanks to Tom for inviting me to contribute this blog-post. I should start by telling you a little about me and how I know Tom, so here goes. I am a PhD student at Royal Holloway, University of London, researching volcano-tectonics and specifically the mechanics of caldera collapses. Like Tom I also studied for a Master’s degree in Volcanology and Geological Hazards at Lancaster University, although we did not meet at Lancaster. I first met Tom in May 2013 for a NEMOH organised field school at Stromboli volcano; where we jointly experienced an unfortunately unforgettable, and particularly rough boat back to the mainland of Sicily. I can highly recommend that if the captain of a sketchy looking boat offers to get you off an island when none of the main companies are willing to, think again! 

So, Tom asked me to write this post as he heard that I was working at a really fascinating and important volcano in Greece. The volcano in question is Santorini, which is a particularly famous stratovolcano in the Aegean ocean. The volcano is famous partly because around 3500 years ago the island experienced a huge caldera forming eruption, which is believed to be associated with the demise of the Minoan civilisation. Deposits from the various phases of the eruption can be seen straddling almost the entire circumference of a north-south elongated caldera, which measures approximately 10 km in maximum diameter, several hundred metres in depth and is centrally filled by ocean. In fact, at least three huge eruptions, ~100 thousand years, ~21 thousand and ~3500 years ago contributed to the shape and size of the current caldera. The global impacts of the Minoan eruption have often been overestimated (see the article of Pyle, 1995), however in terms of volume this eruption is up there with the biggest of the past 10,000 years. Active volcanism in Santorini is now constrained to a small island named Nea Kameni, located almost in the centre of the caldera. This resurgent volcano has been the site of several predominantly effusive eruptions, the latest of which occurred in 1950. Importantly, the island of Santorini lies on top of two north-east to south-west trending faults, one in the north of the island is called the Colombo fault and the other which is believed to be associated with the current phase of volcanism lies directly under Nea Kameni, and is named the Kameni fault.

OK, so what was I doing in Santorini? The answer is looking for and studying dykes in the caldera walls. Just so you’re up to speed, a dyke is a magma-driven fracture through which all volcanic eruptions must be fed. As such, it is really important to know the conditions for dyke propagation in a volcanic edifice. Luckily there are many fantastic geological locations (e.g. Iceland/Tenerife) around the world where geologists can see deep inside ancient volcanoes. In doing so it is possible to observe that many dykes (if not most) never reach the surface, and therefore never contribute to a volcanic eruption. They become arrested. 

Santorini is a stratovolcano made up of many layers of contrasting mechanical properties; for example, stiff lava flows and comparatively compliant layers such as ash, volcanic tuffs and breccia’s. So it offers a great opportunity to try to understand how dykes pass through these individual layers. Specifically, I went into the field to take measurements on the thicknesses, directions and compositions of individual dykes. The walls of the caldera are very steep and largely inaccessible, so most of my work was conducted from a boat, which was a really cool experience. The data is important for me because I am trying to understand how calderas form in different volcanoes. I am using the propagation of dykes as a proxy for the propagation of caldera fractures, because presumably the fracture which created the current caldera must have passed through the same materials with which these dykes also passed. 

In 2011, Santorini experienced an unrest period characterised by elevated levels of seismicity and uplift (see Parks, 2012 for details). Such signals are most likely associated with magma being transported as dyke from great depths, to recharge a shallow magma chamber. When and why a magma chamber ruptures and sends a dyke to the surface is still a reasonably poorly understood phenomenon. So the important question at most caldera volcanoes is: when does a period of unrest lead to a volcanic eruption? It is a difficult one to answer!     

As well as gathering data for my PhD I also took the time to help out at the run-off erosion intensive field-course organised by the University of Athens. Sandy Drymoni  and I ran the course’s final day visit to Nea Kameni, where we introduced some basic volcanological concepts and described some of the islands features. This was a very rewarding and enjoyable experience. The previous day I also had the opportunity to meet the mayor of Santorini at a visit to the Minoan ruins at Akrotiri. Although I wasn’t able to question him about the island’s volcanic preparedness, this was partly out of courtesy, but mainly because we didn’t speak any of the same languages.

I will now use the data collected from this fieldwork as an input for numerical models using the structural mechanics module of a program called COMSOL. In doing so, I will try to understand the stress conditions required for dyke propagation; caldera formation and magma chamber rupture in different types of volcanic edifice.

The receival of a last minute NERC Impaft Fund has meant a mad dash to be ready for a sampling session at Vulcano. The volcano which all others take their name! I am quite excited about adding another volcano to my growing list.

So....what do I do to prepare for fieldwork. One of the first things you do is check all the main equipment is working! In this case, I am developing a new technique which means a brand new Matlab Application finished the Friday before I leave! Hopefully its suitably free of bugs! Next I list the equipment I need, check I know how to use it and I have plenty of spare batteries.

As always, last minute clothes packing and as always I forget one thing...this time it was deodrant...

Vulcano is one of the Aeolian Islands (which includes Stromboli, Lipari) and is fantastic for remote sensing for the majority of the year because of generally good measurement conditions and persistent fumaroles at the La Fossa Crater! Its easily accesible by boat from Milazzo.

So, here I am writing this blog on the pier in Milazzo after surviving two days of driving in Palermo (one Italian told me if you can drive in Palermo you can drive anywhere) and the North coast of Sicily! I am going to try and do a little bit of tweeting/blogging from the field if I have time!

Its certainly a great feeling to get that first publication (with colleagues of course!) under my belt on the creation of a technique for capturing high time resolution fluctuations in CO2 at a 1 s interval, published in the Journal of Volcanology and Geothermal Research. To the right is the location of the study, the NEC of Mt Etna, one of the more frequently used pictures on my blog! The picture is taken from the Pizzi Deneri Observatory. So, how did we produce the dataset, and why is it important? 

Firstly, the ability to directly measure CO2 with traditional remote sensing techniques is difficult, primarily because of the very high atmospheric background levels of the gas! We therefore combined the use of ultra-violet cameras (for more info see Mori and Burton, 2006) to measure SO2 and an instrument called a Multi-GAS analyser (for more info see Aiuppa et al. 2005) which has the ability to measure CO2/SO2 ratios. We can then combine the two sources of data to produce a CO2 flux series.

So, why is the ability to view CO2 at 1 Hz important? Simply put, CO2 exsolves from magmas at greater depths than the other common volatiles H2O and SO2. We can therefore get a better idea of any fresh injection of magma into storage systems if we have detailed records of CO2 emissions. Prior to this point (to my knowledge anyway!), it hasn't been possible to directly compare CO2 emissions at this high rate (of 1 Hz) with other volcanic information, such as seismic and infrasonic data. As a result we reveal interesting trends that may be shared between CO2, SO2 and seismicity. For more information see the paper!

Below is the "AudioSlides" presentation created for the paper, which is great by the way, it has to be less than 5 minutes long and certainly condenses any paper into an easily digestible format, I would certainly encourage others to do something similar! 

In a fantastic end to the first day of VMSG a "Rubbish Bin Volcano" was exploded, using liquid nitrogen similar to this previous example from the University of East Anglia. On the right I am ashamed to say is my poor poor attempt at painting the University of Sheffield name onto my duck. Needless to say, art, or hand-writing of any sort is not my strong point! Although I did manage to get some great glow-in-the-dark paint from Hobbycraft... Anyhow, below is the video of the volcano below, if you were there, you can relive the 'eruption', if you weren't here it is for the first time! It's certainly a great example and analogue for the rapid expansion of gas, ash (and ducks) at the beginning of an explosive eruption. You can also see the 'eruption' in thermal infrared here.

The rest of the day was devoted to posters/talks on intra-plate volcanism and rifting, with tributes to the late Barry Dawson. A broad mixture of talks today on topics ranging from Kimberlites, Feripicrites and the fantastic carbonatite lavas of Oldoinyo Lengai. It was great to hear Mike Widdowson talk about the recent 2013 Nature Geoscience paper on the Shatsky Rise Oceanic Plateau and the discovery that the Tamu Massif could be the largest shield volcano on Earth.

The fantastic thing about modelling volcanic activity is that we can take our current understanding of the physics surrounding a volcanic problem and apply it safely at a desk. It may not be as exciting as being 'out in the field' but is certainly as valuable as we always need real world data to validate and verify models! Modelling activity takes many forms from investigating the dispersal of ash in the atmosphere for aviation, certainly a very prominent and current problem, to analysing potential lava flow paths, vital for determining potential construction sites. The other arguably most valuable thing about modelling is that it often enables us to see things that we otherwise wouldn't be able to view. For example sub-surface processes such as the motion of magma and gas beneath the surface, which just happens to be my modelling area.

When involved with computational modelling, we try to constantly balance between levels of accuracy, an appropriate representation of the physics involved, computational power, solution time and storage space.

• Accuracy - when running a model you first have to define your area (or geometry), in my case its usually just a simple elongated rectangle. Great! I hear you say. Then we have to mesh the domain, that is define a grid which snaps onto our defined geometry. This is where it starts to get more complex, what kind of mesh do we use, do we make it adaptive (i.e. alters during model run), and the key thing what resolution do we use - too small and solution time may take an eon (and also produce unmanageable amounts of data), too large and we may not be able to represent the physics of the problem sufficiently!
• Appropriate representation of the physics - what equations are we going to use? Are they appropriate for the situation? How long do they take to solve?  
• Computational Power - I can guarantee that this is often the major problem for modellers. I am lucky, in that I have access to the University of Sheffield supercomputer Iceberg (don't ask me why its called that but it sounds cool!) to run applications off and hence a large amount of RAM to draw off. During my MSc I was on the other end of the spectrum, using a desktop computer with 2GB of RAM, waiting 3/4 days to perform 30 s of a model run (probably an under-exaggeration actually). From this you can certainly start to see the challenges mounting up!
• Solution Time - As mentioned above, solution time is certainly key, some climate models can take months to run, which if you are doing a 3 year PhD doesn't leave much room for error! It is therefore inherently important to plan model runs for available time and with available resources.
• Storage Space - In a world where data is easy to create but costly to store this is another key issue. Some of my recent model runs have produced >20 GB of data for just 10 s of model run (and took over 10 hours), when preforming multiple model runs it is obvious that cumulative data production will get larger and quickly run into the terabytes. Some ways of getting around this include only exporting/saving the data you actually need, if your only interested in temperature outputs only save this!

There are many excellent fluid dynamics software applications in existence, however, they are usually costly (running into the tens of thousands, notable exception here is OpenFoam). It is lucky therefore that the University of Sheffield has access to one of the leading applications Ansys and the dynamic Ansys Fluent package. Below is an example of Ansys Fluent model run, simulating the rise of a volcanic slug, generally believed to be the cause of strombolian eruptions at the such volcanoes as the archetypal Stromboli. Cheaper applications such as Matlab, certainly offer the ability to perform, less complex physics problems but lack the user-friendly interfaces such as Ansys and necessitate an in-depth knowledge of the maths and physics behind the problem!

I am sure I have missed many considerations off here, but these are just a few tasters!

It is vitally important that models are not just used on their own, as there is nothing to calibrate or validate the model against. The best way of modelling is by comparing observations in the field, in my case gas emissions, with laboratory proxies, and models. Anyhow, when weighing all of these points against the benefits, a clear and greater understanding of environmental processes is essential and is something which can only occur with significant modelling of processes.

Below is an example simulation of a taylor bubble (or slug) rising through a tube as a proxy for the root cause of a strombolian eruption (the type seen at stromboli).

Recent research published in Geophysical Research Letters by Tamburello et al. (2013) has demonstrated that Sulphur Dioxide emissions can vary rapidly over very short timescales during passive degassing (see previous post for info on passive degassing). The study also demonstrates that there are links between the emission of Sulphur Dioxide and Seismicity over certain periods. This is achieved by taking high resolution readings of Sulphur Dioxide using UV cameras every second or so, which allows the comparison of the Sulphur Dioxide and Seimsic datasets at this high resolution. 

Great! But what does this mean? In short it means that the two process are potentially linked over these timescales, which could implicate that gas emissions are driving seismicity (I am sure there are other possibilities though...). It confirms that volcanoes such as Etna are very dynamic and that sub-surface processes (which almost inevitably cause these fluctuations) rapidly alter the gas emissions that are recorded at the surface (or vice-versa). This is where my PhD research kicks in, why are we seeing these changes over these timescales? What is causing these very periodic structures? Of course this trend in emissions is not just seen at Etna but at other volcanoes worldwide. It could therefore be important for understanding the state of shallow magma pathways and storage areas in basaltic systems generally.

The US government shutdown a few days ago and it has already begun to have a severe impact on people's lives and potentially the stability of the US economy if it continues much longer. This is not a political blog (although I am interested in such things sometimes) so I thought I would take a brief look at how it will effect volcanology. First things first, potentially one of the most obvious effects, the Smithsonian institution is closed which means no more volcanic updates. This also includes the weekly volcanic update which I am sure most agree is an invaluable source of reliable information on present eruptions, something which will not occur until this shutdown ends.

What about national parks? Log on to the National Park Service website and the message on the right appears - all national parks are closed, this includes valuable tourist destinations such as Yellowstone National Park (to my knowledge anyway!). The wonderful natural attractions which support so many jobs and attract many tourists will not be able to be visited. I am certainly glad that I got my visit in earlier in the summer! It is not also the national parks which are affected but the Volcanic Observatory's as well. The following is taken from the USGS Hawaiian Volcano Observatory website:

Reading between the lines, what does this statement mean? Well first things first, volcano monitoring will continue so air traffic updates will continue keeping aircraft safe and people in case of an event or a change in hazard status (no need to worry on that point then!). An increased workload for employees will likely however be an undesired effect. Volcanic monitoring instruments often need frequent calibration, checking or repair to keep them sending reliable information to observatory's, as such the shorter the shutdown the better. However, the longer it continues the number of instruments in operation will decline but also the reliability of the data which will not only be bad for science (i.e. less science will be done with a reduction in instruments and quality of data) but bad for volcano monitoring. Of course after the shutdown ends, whenever that might be, it will take longer to repair or check equipment and generally get up and running again. I certainly detect a bitter undertone in the statement directed at the US government as it will likely create a large backlog of work. 

Here's to hoping the shutdown ends soon for more reasons than just volcanological!

Another year, and another return to the Pizzi Deneri observatory for more Sulphur Dioxide gas measurements. One of the things which never ceases to amaze me whilst around the summit of Mt. Etna is the large numbers of ladybirds (ladybugs/cocchinella?) that are littered across the landscape. This particular group (photo on right) was found on the bottom of a rock, quite incredible!

This time the weather was a little better overall than last year. However, when remote sensing things are a little bit more complex when looking for the 'perfect' measurement weather. This year, we were lucky, not too many optically thick clouds which cover the summit and in general a good plume location and direction. Below is a photo taken from La Montagnola of the South East Craters. Unfortunately Etna decided not to wake up fully during my visit, oh well, that just means I may get to go back sooner! Must keep an eye on those webcams!

A little side project of mine over the past few weeks has been experimenting with the optical properties of very cheap web cameras, this one in particular costing around £6, roughly $10. The average web camera has what is called a CMOS sensor installed which allows detection of light in the wavelengths roughly between 400 and 1000 nm. In practice this means the 'Visible Spectrum' between roughly 400-700 nm and part of the near-infrared spectrum as well. However, installed in most of these cameras is an infrared filter (the slight reddish tint on the picture of the lens). It is relatively simple to remove this filter, unfortunately on this particular camera it is not possible to remove it intact but I didn't want it leftover anyway! 

After removing this filter, I reassembled the webcam and went to the park just by the geography department. Here I took a 'Full Spectrum' image (left below) and one with a visible light filter (in one specific wavelength - right below). I am sure you can agree the results are very cool! There are a number of things you can use for cheap visible light filters, you may even have one of them lying around the house or in a dusty cupboard somewhere. A very simple option is to use a black bin liner or an exposed camera negative which is as dark as possible.


Why not try it yourself, it is very easy to do and takes no time at all. There are many applications of this sort of photography including night vision (generally using a separate infrared light source), looking at absorption of greenhouse gases and general coolness!

For all the eagle eyed people who read my blog you may have noticed that I have recently added a page to my blog called "Codes". I have now started adding files to this page and also to vhub - which, for those of you who don't know is short for  the Volcano Hub (I assume so anyway!). It is an insanely awesome resource for an immensely broad array of random and useful volcanic material.

All of the code currently listed is described fully in the two separate areas, so I won't bore you with details here!

Here are the links to my files on vhub:
Stokes Rise calculations 
Normalising datasets in Matlab
Magma Density 
Magma Viscosity 

Any questions/comments on these please don't hesitate to contact me.