Imaggeo on Mondays: Spectacular splatter – the marvels of a mud volcano

28 Jul

Mud volcanoes, unlike many others, do not extrude lava. Instead, they release glutinous bubbling brown slurry of mineral-rich water and sediment. They range in size from several kilometres across, to less than a metre – the little ones are known as mud pots, reflecting their diminutive nature. The world’s largest, though, is Lusi: a mud volcano in East Java that released an astonishing 180,000 cubic kilometres of fluid each day during the peak of its 2006 eruption. It’s likely to continue erupting for another 26 years!

Much of the gas that bubbles up through these muddy pools is methane, though the exact mix of gasses varies from site to site and is tied to other geological activity in the region, with those close to igneous volcanoes often releasing less methane than those associated with clathrate deposits. Small bubbles of gas can coalesce to form a much larger one, which, on reaching the surface, bursts and sends flecks of clayey fluid asunder, just as they do here:

The sediment-rich spatter from a bubbling mud volcano. (Credit: Tobias Heckmann via imaggeo.egu.eu)

The sediment-rich spatter from a bubbling mud volcano. (Credit: Tobias Heckmann via imaggeo.egu.eu)

By Sara Mynott, EGU Communications Officer

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

 

Geosciences Column: The Toba eruption probably did have a global effect after all

25 Jul

Almost everyone has heard of the Toba super-eruption, which took place on the island of Sumatra roughly 74,000 years ago, but the only evidence of tephra or tuff (volcanic fragments) from the eruption is in Asia, with nothing definite further afield. It has sometimes been thought that this huge eruption may have led to a volcanic winter, a period of at least several years of low temperatures following a large eruption. This is caused by the effect of enormous quantities of volcanic ash entering the atmosphere and reducing the sun’s penetration. Sulphides also help to reduce solar energy penetration and increase the Earth’s albedo (increasing the reflection of solar radiation and leading to cooler temperatures).

In a 2013 study, Anders Svensson and colleagues suggest that a link has now been made between the onset of Greenland Interstadials (GI) 19 and 20 and Antarctic Isotope Maxima (AIM) 19 and 20 for the Toba eruption. Stadials are periods of low temperatures, lasting less than a thousand years, during the warmer periods between ice ages. Conversely, interstadials are warmer periods lasting up to ten thousand years, occurring during an ice age but not lasting long enough to qualify as interglacial periods. The GI periods and AIMs are numbered according to a scale based on Dansgaard-Oeschger events. These are relatively short-lived climate fluctuations, which occurred 25 times during the last glacial period (covering 110,000 to 12,000 years ago) and are used to help date events.

The study’s claim is based on their matching of volcanic acidity spikes at both poles produced by increased sulphur compounds in the atmosphere following the Toba eruption, which have been matched to the existing dates based on Asian tephra records and the bipolar seesaw hypothesis. This hypothesis explains the thousand-year offset between temperature changes over the two poles during the last glacial period as being caused by a seesaw mechanism involving heat redistribution by the Atlantic Meridional Overturning Circulation (AMOC) system, whereby warm water moves north from southern waters, mixes with cooler water in Arctic regions, sinks, and returns south as deep bottom water.

The fluctuations in temperature associated with Dansgaard-Oeschger events over a few decades are reflected in Greenland ice cores but Antarctic ice cores show a picture of slower changes over hundreds to thousands of years, running out of phase with the Greenland records. A direct link was made by Carlo Barbante and colleagues in a 2006 paper. They used methane records from a Northern Greenland ice core and oxygen isotope records from the Antarctic Dronning Maud Land ice core to show direct coupling between warm events in the Antarctic and the duration of cold events in Greenland indicating their probable common origin in a reduction in AMOC.  An increase in freshwater entering the North Atlantic during warming would slow heat transport towards the north. This would lead to cooler surface air temperatures there and warmer temperatures in the southern waters and vice versa – taking several decades to pass from one hemisphere to the other, hence the name bipolar seesaw effect.

When volcanic gases, especially sulphurous gases, travel round the world in the atmosphere they form aerosols, which are trapped with air in precipitation at the poles in the form of bubbles. The bubbles are entombed at the depth at which firn (a type of rock-hard snow that looks like wet sugar) is compacted into ice. Succeeding precipitation and compaction over thousands of years provides evidence of atmospheric composition at different times, in trapped air bubbles, which can be analysed in ice cores. But the ages of both ice and gases are offset by 100-1000 years, depending on factors such as thickness of the firn, temperature and the presence of impurities in the ice. Ice cores are a bit like tree rings in that their thickness and other properties reflect climatic conditions at the time and differences can be counted as annual rings for the younger cores, before compaction makes it impossible to distinguish them.

Isotope data for Greenland and Antarctic ice cores over the past 140,000 years. (Credit: Leland McInnes)

Isotope data for Greenland and Antarctic ice cores over the past 140,000 years. (Credit: Leland McInnes)

Oxygen isotope and atmospheric methane signals in ice cores were available to link two separate records (NGRIP and EDML) for the period covering 80-123 thousand years ago.

Different gases can be used to date a particular part of an ice core and, as can be seen above, δ2H in Antarctica and δ18O in Greenland were used for dating purposes. 10Beryllium is found in the atmosphere and its levels change with solar activity and the Earth’s magnetic field. It is only found in the atmosphere for one or two years at a time so it can be used to help synchronise data from different ice cores more closely. A dating method using cosmogenic 10beryllium signals to match both Greenland and Antarctic ice cores to the Laschamp geomagnetic event (a short reversal of the Earth’s magnetic field). This helps pinpoint a particular date at around 41 thousand years ago, and provides a direct link between the ice-core horizons so that the data could be matched and signs of the eruption detected at the known eruption time.  With markers for 41,000 and 80,000 years ago synchronised for the two polar regions, the ice cores were examined for signs of sulphate acidity spikes indicating a major eruption.  The time scales were then combined for datasets from a number of ice cores (NGRIP, EDC, EDML and Vostok) to produce consistent scales for ice and gas records.

From the Greenland (NGRIP) and Antarctic (EDML) ice-core data, evidence of the Toba eruption was synchronised between them for approximately 2000 years around the known eruption time, using a pattern of bipolar volcanic spikes and the Greenland Ice Core Chronology 2005 defined for the NGRIP annual layer count, to compare with Antarctic data. They found evidence of large quantities of atmospheric sulphates (usually linked to volcanic eruptions) in both sets of data in the form of acidity spikes and linked these to the Toba eruption.

In fact, there are four bipolar acidity spikes within a few hundred years of the presumed Toba event, suggesting that there may have been several events, also confirmed by argon dating. Moreover, the authors found that the Toba eruption was linked to up to 4 acidity spikes occurring between 74.1 and 74.5 thousand years ago. These Toba events occurred at a time of rapid climate change from warm interstadial to cold stadial periods in Greenland and the equivalent Antarctic warming within 100 years, which perfectly agrees with the bipolar seesaw hypothesis.

Interestingly, another more recent study, showed that Lake Prespa in southeast Europe reached it’s lowest recorded level, or lowstand, at the time of the Toba eruption. The timing of the lowstand is dated at 73.6 ± 7.7 thousand years ago based on Electron Spin Resonance dating of shells. This short-lived lowstand also coincides with the onset of Greenland Stadial GS-20, with a possible link to the Toba eruption.

This new data and more accurate dating described in these studies, does tend to show that the Toba eruption (or series of eruptions) did, in fact have global impact.

By Gill Ewing, Freelance Science Writer

References:

EPICA Community Members: One-to-One coupling of glacial climate variability in Greenland and Antarctica, Nature, 444, 195-198, doi. 10.1038/nature05301, 2006.

Svensson, A., Bigler, M., Blunier, T., Clausen, H.B., Dahl-Jensen, D., Fischer, H., Fujita, S., Goto-Azuma, K., Johnsen, S.J., Kawamura, K., Kipfstuhl, S., Kohno, M., Perrenin, F., Popp, T., Rasmussen, S.O., Schwander, J., Seierstad, I., Severi, M., Steffensen, J.P., Udisti, R., Uemura, R., Vallelonga, P., Vinther, B.M., Wegner, A., Wilhelms, F. Winstrup, M.: Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 KaBP), Clim. Past, 9, 749-766, doi. 10.5194/cp-9-749-2013, 2013.

Wagner, B., Leng, M.J., Wilke, T., Böhhm, A., Panagiotopoulos, K., Vogel, H., Lacey, J.H., Zanchetta, G., Sulpizio, R.: Distinct lake level lowstand in Lake Prespa (SE Europe) at the time of the 74 (75) ka Toba eruption, Clim. Past, 10,  261-267, doi.10.5194/cp-10-261-2014, 2014.

Open geoscience

23 Jul

Not so long ago I was in a meeting with EGU’s young scientist representatives, who had gathered online to discuss the issues facing those early in their academic careers. One member of this dedicated team put forward a compelling notion: that the future of open access is in the hands of today’s early-career researchers. This post aims to answer the question that followed: “how could EGU’s team of eager early-career researchers help their peers grab hold of the open opportunities out there?” by offering up a few routes to open science…

A lot of hard work, carefully created figures and data don’t make it to your publications, but they are still a useful part of the scientific process and can help other scientists if they can see what you found. A great way to share this sort of information is on Figshare – and it’s citable too.

The same goes for conference presentations – don’t let them gather dust on your desktop. The aim of a conference is to share your work more widely, so, when you’re done, put your slides up on sites like SlideShare to share it beyond the conference. Keep your contact details in the presentation and you could find yourself with new collaborators.

Open the doors to more collaborative geoscience. (Credit: Oxyman)

Open the doors to more collaborative geoscience. (Credit: Oxyman)

Posters can be made open too. After our annual General Assembly, we invite authors to upload their posters and presentations, but there’s no need to restrict your openness to the EGU conference. F1000 posters is an open access repository for posters in biology, so if your work bridges the biogeosciences, be sure to submit it there. If you’re in another field, try Figshare (despite the name, it’s not just for figures!).

The EGU offers a number of open access journals for the Earth, planetary and space sciences, but there are many more journals where you can publish your work, if the scope of EGU journals doesn’t quite cover your field. The American Geosciences Institute hosts a comprehensive list of open geo journals on their website, and the Directory of Open Access Journals is exactly what it says on the tin – a hub of high quality open access publications. The stringent criteria required to enter their database means that predatory open access journals are filtered out.

But what about impact? Going open doesn’t mean lower impact, in fact, with your paper being openly available to all, it’s more likely to be seen and cited, so the impact at the article level could well be higher than if it was in a subscription-based publication. You can track the impact of your research outputs using ImpactStory, or by using the Altmetric bookmarklet to keep tabs on more than just citations, from where it’s featured in news articles and blog posts to where it’s been mentioned on social media and more.

Don’t let your work gather dust. (Credit: How Matters)

Don’t let your work gather dust, share it. (Credit: How Matters)

The European Research Council considers that providing free online access to publications is the most effective way of ensuring that the fruits of the research it funds can be accessed, read and used as the basis for further research. Many funders are also moving in this direction, providing further incentive to publish open access papers.

When your manuscript is ready, submit it to a preprint server (e.g., arxiv.org, peerj.com, or biorxiv.org). EGU papers have an open review process, which helps ensure the assessment of a submitted manuscript is thorough and fair, but it also means that the science is out in the open sooner – the merit of a preprint. This helps establish precedence, highlighting that you were working on something first, and can remove barriers to scientific progress (we all know peer review can take a while!). Some establishments aren’t a fan of this though; so before you put a preprint online, check Sherpa/Romeo to make sure your institute, funding body and the journal(s) you’re interested in are on board with the benefits of preprints.

Models are near ubiquitous in the geosciences and their importance in assessing the impact of climate change goes without saying. But what if you couldn’t replicate the results of, say, an important climate model? You would need to go back to the model’s code and see where your calculations and the ones before differed. Sharing code is compulsory for journals like Geoscientific Model Development, but many don’t stipulate the need to share it. You can go one step further to help your community by sharing your code on GitHub, whether it’s compulsory for your latest article or not.

Free the work from your desktop folders. (Credit: opensource.com)

Free the work from your desktop folders. (Credit: opensource.com)

With all these opportunities to go open, wouldn’t it be great if you had an opportunity to keep track of all your outputs? There’s an answer for that too – ORCID. ORCID is a unique researcher identifier that links all your research outputs, from manuscripts and conference abstracts to grant submissions and research figures, ensuring you get credit for the work you do.

For something less formal, but perhaps more open in that you can go beyond the academic community, try blogging about your research – we readily welcome guest posts here on GeoLog, but there are many places you can set your science free. Try The Conversation, SciLogs, pitching your idea to another geoscience blogger or better yet, establishing your own blog to write on. You can also go further to promote your research and facts about your field on social media – a great way to form connections with other academics and put your work in the public eye.

These are just a few thoughts on open geoscience, but there are likely more ways go open than could ever be summarised in a single post. Take this is a starting point, seek out more options for yourself, and, if you already have a few tips on how to make geoscience more open, spread the word.

By Sara Mynott, EGU Communications Officer

If you have any thoughts on other ways geoscientists can move towards open science, please add your thoughts to the comment thread below. 

Imaggeo on Mondays: Entering a frozen world

21 Jul

Dmitry Vlasov, a PhD Student and junior scientist from Lomonosov Moscow State University, brings us this week’s Imaggeo on Mondays. He shares his experience of taking part in a student scientific society expedition to Lake Baikal.

This picture shows icy shores of Lake Baikal – a UNESCO World Heritage Site and the world’s largest natural freshwater reservoir (containing about one fifth of Earth’s unfrozen surface freshwater). It is also the deepest lake on our planet (1,642 m).

The icy shores of Lake Baikal. (Credit: Dmitry Vlasov, via imaggeo.egu.eu)

The icy shores of Lake Baikal. (Credit: Dmitry Vlasov, via imaggeo.egu.eu)

The aim of the expedition was to do an eco-geochemical assessment of the environment in and around Ulan-Ude (the capital of Republic of Buryatia). Snow samples were collected all around the city to determine their chemical composition and the concentrations of different chemical elements present in the snowpack. We also studied the isotopic composition of snow to help find the sites where air masses form.

Weather-wise, we were lucky – according to locals this winter was a warm and snowy one. The temperature was (only!) -25 to -33 degrees Celsius. Times were tough when strong, cold and piercing winds froze our hands and faces.

To find out the impact of transport and industry on the snow’s chemical composition within the city, we took background snow samples at different distances and in and around it. One such area was set to the northeast of the city, close to the Turka and Goryachinsk settlements across the notch from Ulan-Ude. This photo was taken in that exact spot. It took about 2.5 hours to make the 170 km journey from Ulan-Ude by car, but we didn’t regret it. The scenery was amazing! The cover of ice over the lake sparkled bright blue, despite being exceptionally transparent. Because of the water’s choppy nature, ice on the Lake Baikal often cracks and billows to form a chain of miniature ice mountains, alternated with relatively smooth ice plains. I’d never seen anything like this before.

All the participants were very excited about expedition – it showed the students different sides of scientific life: work in rather hard weather conditions, analytical lab studies, route planning and of course the breathtaking beauty and outstanding power of nature.

By Dmitry Vlasov, PhD Student and junior scientist, Lomonosov Moscow State University

Acknowledgement:

The expedition was carried out with the financial support of the Russian Geographical Society and the Russian Foundation for Basic Research (project № 13-05-41191 and project RGS “Complex Expedition Selenga-Baikal”).

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

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