GeoLog

Sessions

At the Assembly: Friday highlights

At the Assembly: Friday highlights

The conference is coming to a close and there’s still an abundance of great sessions to attend! Here’s our guide to getting the most out of the conference on its final day. Boost this information with features from EGU Today, the daily newsletter of the General Assembly – pick up a paper copy at the ACV entrance or download it here.

Be sure to attend today’s Jean Dominique Cassini Medal Lecture by Jonathan I. Lunine, who will be discussing habitable environments and life in the Saturn system (ML4, 12:15 in Y1).

It’s your last chance to make the most of the networking opportunities at the General Assembly, so get on down to the poster halls and strike up a conversation. If you’re in the queue for coffee, find out what the person ahead is investigating – you never know when you might start building the next exciting collaboration! Here are some of today’s scientific highlights:

The final Union Symposium (US4) this week is dedicated to planetary interiors and how advances in space observations have furthered our ability to understand what is inside planetary bodies. Talks begin at 08:30 in Y5. Our final Great Debate of the week, which is co-organised with the AGU (American Geophysical Union), will be on open access publishing. The discussion kicks off at 15:30 in Room R1.

Today we also announce the results of the EGU Photo Contest and the Communicate Your Science Video Competition. Head over to the EGU Booth at 12:15 to find out who the winners are.

Following the success of this year’s theme, EGU 2016 will also have a theme: Active Planet. Join us on this adventure in Vienna next year (17–22 April 2016)!

What have you thought of the Assembly this week? Let us know at www.egu2015.eu/feedback and help make EGU 2016 even better.

We hope you’ve had a wonderful week and look forward to seeing you in 2016!

Nibbling round the edges. Credit: Maria Hernandez-Soriano (distributed via imaggeo.egu.eu)

Nibbling round the edges. Credit: Maria Hernandez-Soriano (distributed via imaggeo.egu.eu)

GeoTalk: Explosive testing with Greg Valentine

GeoTalk: Explosive testing with Greg Valentine

Following his session at the EGU General Assembly, Greg Valentine (Buffalo University) spoke to Sara Mynott about how he creates model volcanoes, specifically maar-diatremes, and blows them up to better understand what goes on in an eruption…

So what is a maar-diatreme?

A diatreme is a vent-like structure, mostly made up of broken up bedrock and magma. Initially, you have a dyke that channels magma straight up to the surface, but somewhere along the line the magma interacts with groundwater. This causes explosions below ground, which start to build up zones of debris. Once you get a debris-filled zone, the magma comes up in fingers that probably facilitate further interaction with water.

Tell me a little about your experiments…

We have an experimental site near Buffalo, New York. It’s out in the countryside, so we can be messy and loud.

We dig a trench (20m long, 4m wide and 2m deep) and make craters between 1 and 2 metres in diameter. It’s like landscaping. We have a guy who normally works in gardens, he comes and digs the trench, and we go shopping at quarries and buy different types of sand and gravel to fill it, bringing in truckloads and truckloads of sediment. But first we add some explosives.

What we’re trying to do is relate what we see in a surface eruption to what goes in the subsurface. In the experiments we can completely control that – from what makes up the sediment layers to the amount of energy and where the explosion occurs.

How much explosive energy do you put into your experiments and how does that compare to what you would see naturally?

We’re working with about a million Joules – it’s about half a stick of dynamite, something like that. The natural explosions are maybe 3 to 6 orders of magnitude larger.

Valentine and his team were standing about 75m away from the explosion, but that didn’t stop a couple of stray rocks landing behind them! Here, the plume is about 15 m high and the clumps of sand that are being thrown out are several centimetres across. The scaled depth? Just right. Credit: Graettinger et al. (2014).

How does the depth and energy of the explosion affect what happens in an eruption?

To tackle this we use this thing called scaled depth, which relates the depth of the explosion to the energy involved. This way of characterising underground explosions has been used for over a hundred years, by people who do mining, geotechnical engineering and weapons testing.

We know that if we have a very small scaled depth, most of the energy goes into the atmosphere. You get a big bang – it’s very dramatic, it’s very fun, you can see the camera shaking when the shockwave hits the camera, but it doesn’t excavate that much of a crater. If you get it too deep, so the scaled depth is really large, nothing comes out. This is because more of the energy is being absorbed by the ground. So there’s this intermediate scaled depth where you get the most crater excavation.

How often do these explosions occur at a particular location or at different depths? Is there any regular pattern at a particular volcano?

We don’t understand enough yet to be able to say that, except that there are probably many – perhaps hundreds – of explosions at a natural maar-diatreme. We suspect that probably more of the explosions happen near the surface because there’s less confining pressure – something that acts against the explosion.

The depth? Too deep. The ground goes up when the shockwave hits it from below, but then it sinks. Look closely – the tennis balls on the surface are used as ballistic markers, but rather than being thrown out in the explosion, they sink as the ground subsides to form a small crater. Credit: Graettinger et al. (2014).

What proportion of the world’s volcanoes are maar-diatremes?

If you just counted each volcano on Earth, not including under the ocean, maar-diatremes would be the second most abundant. They tend to be what we call monogenetic – they have one eruptive episode that may be a few weeks to a few years long and they’re dead.

Usually, they occur in what we call volcanic fields, which, instead of having one central cone, have many small volcanoes over an area. There are many such fields in Europe, including Chaîne des Puys in France and Campi Flegrei in Italy. A volcanic field may have an eruptive period every 1,000 years or so, some more frequent and some less frequent.

What risk do maar-diatremes pose to the human population?

Many of these volcanic fields are inhabited. If an eruption occurred close to Naples, there would be tens to thousands of people affected. Auckland, New Zealand, is almost entirely built on a young volcanic field. It’s dormant right now, but sometime something will happen. Mexico City is another one.

If an explosion were to occur close to the surface in one of these places, what impact would it have?

It could make a crater that is 100-200 metres in diameter and throw blocks – big rocks – 100s of metres from the volcano, probably generate a lot of ash and pyroclastic flows.

What do you love most about your job?

The flexibility to pursue different lines of research wherever they take me.

Finally, what advice would you give a young scientist wanting to get into experimental volcanology the way that you have?

They should make sure they have a good physics and math background, try to get an internship with somebody and just dive in!

 

By Sara Mynott, Press Assistant at the 2015 General Assembly and PhD student at the University of Exeter.

 

References

 Valentine, GA, Graettinger, AH and Sonder, I.: Phreatomagmatic explosive eruption processes informed by field and experimental studies. Geophysical Research Abstracts, Vol. 17, EGU2015-1896, 2015.

Valentine, G. A., Graettinger, A. H., Macorps, É., Ross, P. S., White, J. D., Döhring, E., & Sonder, I.: Experiments with vertically and laterally migrating subsurface explosions with applications to the geology of phreatomagmatic and hydrothermal explosion craters and diatremes. Bulletin of Volcanology, 77(3), 1-17, 2015.

Graettinger, A. H., Valentine, G. A., Sonder, I., Ross, P. S., White, J. D. L., and Taddeucci, J.: Maar‐diatreme geometry and deposits: Subsurface blast experiments with variable explosion depth. Geochemistry, Geophysics, Geosystems, 15(3), 740-764, 2014.

Valentine, G. A., Graettinger, A.H. and Sonder, I.: Explosion depths phreatomagmatic eruptions. Geophysical Research Letters, 41 (9), 3045-3051, 2014.

At the Assembly: Thursday highlights

At the Assembly: Thursday highlights

Welcome to the fourth day of General Assembly excitement! Once again the day is packed with great events for you to attend and here are just some of the sessions on offer. You can find out more about what’s on in EGU Today, the daily newsletter of the General Assembly – grab a copy on your way in or download it here.

The first Union-wide session of the day focuses on geophysics and resilience and what is at stake (US3). The talks at this session will critically analyse large-scale projects that have been developed in order to increase resilience to geophysical extremes in Europe and elsewhere. Discover more from 13:30­–17:00 in B14.

Thursday also sees another interesting Great Debate take place: Negotiating climate policy – resigning to resilience? (GDB3, from 15:30–17:00 in Y1). With nations striving to negotiate a new global climate change agreement in late 2015 in Paris, there are two possible avenues that humanity can choose: pursue negotiations and achieve a solution that combats global warming, or put more effort on adaptation and resilience building. During the debate the panel will discuss emission scenarios and related climate consequences. Tune into to the session on Twitter using the #EGU15GDB hashtag or online at http://www.egu2015.eu/webstreaming.html.

Today’s interdisciplinary highlights include sessions on…

Take the opportunity to expand your skills in one of today’s short courses and splinter meetings:

There’s also a number of medal lectures on throughout the day – here’s a sample of what’s on offer:

What have you thought of the Assembly so far? Let us know at www.egu2015.eu/feedback, and share your views on what future EGU meetings should be like!

If you need a change of pace, stop by the Imaggeo Photo Exhibition beside the EGU Booth (basement, Blue Level). You can vote for your favourite finalists there and – while you’re in the area – take the opportunity to meet your Division’s representatives in today’s Meet EGU appointments. While on the subject of competitions, make sure to ‘like’ your favourite Communicate Your Science Video Competition film on the EGU YouTube channel.

Have a lovely day!

Credit: David Bernard (distributed via imaggeo.egu.eu)

Credit: David Bernard (distributed via imaggeo.egu.eu)

At the Assembly: Wednesday highlights

At the Assembly: Wednesday highlights

We’re halfway through the General Assembly already! Once again there is lots on offer at EGU 2015 and this is just a taster – be sure to complement this information with EGU Today, the daily newsletter of the General Assembly, available both in paper and for download here.

Today features more Union-wide events which celebrate the conference theme: A Voyage through Scales. First up is a symposium on the geocomplexity of scales (US1): a series of talks which will explore the variability of geosystems over a huge range of scales both in space and time. This is followed by a Lecture of general scientific interest (GL2) in the afternoon on archives of the continental crust by Chris Hawkesworth, which you can join in Y1 from 13:30 onwards. You can follow the sessions on Twitter with #EGU15US and #EGU15GL, and, if you’re not attending, tune in with the conference live stream.

The educational and outreach symposia (EOS) feature sessions on geoscience education, science communication, public engagement and related topics. This year there are a large number of EOS sessions on offer: today you could head over to the geoethics for society: general aspects and case studies in geosciences session, from 13:30–17:00 in Room R12, where talks will focus on the ethical and social implications in geoscience. Make sure to check the EOS programme to see if anything else catches your fancy.

Another promising event set for today is the EGU Award Ceremony, where the achievements of many outstanding scientists will be recognised in an excellent evening event from 17:30–19:00 in Room Y1. Here are some of the lectures being given by these award-winning scientists:

Today also sees the Penck Lecture of the Geomorphology Division take place. Ann V. Rowan will be talking about what can mountain glaciers tell us about climate change: quantifying past and future discharge variations in the Southern Alps and Himalaya (KL2) from 12:15–13:15 in G2.

Now on to short courses! Today offers the opportunity to learn how to write the perfect paper in geomorphology (SC47/GM11.2, 17:30–19:00 in G2), learn the basics of climate modelling (SC43, 19:00–20:00 in B12) and increase your chances of securing funding for your next project by attending this two part workshop: How to write a successful ERC Starting Grant proposal (SC19/TS10.1, 15:30–17:00 / Room B4), followed by the broader, finding funding: how to apply for a research grant (SC39, 17:30–19:00 / Room B13).

And check out some of today’s stimulating scientific sessions:

Finally, remember to take the opportunity to meet your division’s representatives in the day’s Meet EGU sessions and, if you’ve had enough of the formalities, head on over to GeoCinema, where you’ll find some great Earth science films, including the finalists of EGU’s Communicate Your Science Video Competition. Make sure to vote on your favourite entries by ‘liking’ the videos on the EGU YouTube channel.

Have an excellent day!

Follow

Get every new post on this blog delivered to your Inbox.

Join other followers: