An island of glass - the explosive history of Pantelleria, Italy

By @volcanologist

If you’ve heard of Pantelleria, it may be because you’ve seen A Bigger Splash, or read about it in a travel magazine extolling its yet undiscovered virtues (unless you are Madonna or Georgio Armani who have holiday homes there). If you’re a geologist, you may know the name from Pantellerite, the name given to peralkaline rhyolites, which are so abundant on the island. Or perhaps, the enigmatic mineral Aenigmatite, also known as Cossyrite after Cossyra, the ancient name of Pantelleria. What you may not know is that Pantelleria is an island of glass and has a history of catastrophic, caldera forming eruptions. Our recent work has pieced together the island’s explosive past in a new, comprehensive volcanic history.

The last eruption to occur at Pantelleria was a submarine basaltic eruption that occurred 4 km NW of Pantelleria in 1891. The eruption lasted for 9 days and produced floating scoria bombs which eventually exploded and sank. But this gentle, effusive basaltic activity is not typical of the island’s history, instead the island more commonly erupts trachyte and rhyolite, regularly covering the island in volcanic glass of one form or another. For the last 46,000 years, eruptions have mostly been small (strombolian in scale) with local pumice fall deposits and lavas. Around 46,000 years ago, a large eruption occurred generating a hot,sticky pyroclastic density current which covered the island in a welded, rheomorphic ignimbrite known as the Green Tuff. The Green Tuff blanketed the island, and covered the older deposits. The older rock record was known to include eruptions of at least the same size as the Green Tuff, but as their deposits are best exposed in dramatic sea cliffs it has been difficult to piece together this story of explosive eruptions until now.

Panoramic view of a section of the sea cliffs on Pantelleria showing the complicated and largely inaccessible geology: a succession of laterally discontinuous lavas and pumice deposits can be seen, draped by ignimbrites at the top. White and cream units are either non-welded pumice fall or PDC deposits.

Our study brings together field volcanologists, palaeomagnetists and experts in radiometric dating to put together the complete story of the pre-Green Tuff eruptions. The field volcanologists carried out detailed studies of the rocks left behind by these older eruptions, interpreting the rocks in order to understand the processes that formed them. The palaeomagnetists used palaeomagnetic data as a correlation tool, to help match up some of the deposits where these couldn’t be easily traced in the field. Finally, we used Ar/Ar radiometric dating so that we know when the different eruptions occured.

General vertical stratigraphy of ignimbrite-producing eruptions on Pantelleria

We find that the island’s history is dominated by large ignimbrite-forming eruptions. Ignimbrites are the deposits of pyroclastic density currents; dramatic hot flows of gas, ash and rocks which can travel at speeds up to 450 mph (to learn more about ignimbrites and how we use them to reconstruct PDCs, read this blog). Some of the ignimbrites are related to eruptions which resulted in caldera collapse. This is where the magma reservoir underneath the volcano is evacuated so dramatically during an eruption that the roof of the reservoir collapses - the volcanic edifice disappears into the space created by erupting the magma. Caldera collapse eruptions are thought to be some of the biggest, most violent eruptions that a volcano can produce. We found that Pantelleria had experienced at least five of these catastrophic eruptions. The Green Tuff eruption is commonly thought to have ended with a caldera collapse event, but recent work suggests that this isn’t the case. These large eruptions occur every few thousand years up to a gap of around ~40 kyr - we found that there didn’t appear to be any cyclicity or pattern to the timing of the eruptions.

Sea cliffs at Scauri. The bump on the right is a small local centre, draped by ignimbrites.

We also found that in between these large eruptions the island was far from quiet. Small scale eruptions were producing eruption columns that covered local areas with pumice, or perhaps generated small lava flows. These ancient small eruptions are very similar to the activity that has occured on the island since the Green Tuff. So then, is the island currently in a phase of activity so very different to the island’s volcanic past? Probably not. Studies on the last 46,000 years have suggested a decrease in eruptive activity, particularly in the last 15,000 years. But we cannot assume that no large, catastrophic eruption will occur in the future. Importantly though, there is no current evidence that an eruption is expected imminently.

Nina J. Jordan, Silvio G. Rotolo, Rebecca Williams, Fabio Speranza, William C. McIntosh, Michael J. Branney, Stéphane Scaillet, 2018. Explosive eruptive history of Pantelleria, Italy: Repeated caldera collapse and ignimbrite emplacement at a peralkaline volcano. Journal of Volcanology and Geothermal Research, 349, 47-73. https://doi.org/10.1016/j.jvolgeores.2017.09.013.

A PDF is available at http://www.sciencedirect.com/science/article/pii/S0377027317300781; from the University of Leicester or Hull’s repository; or by emailing Nina Jordan or Rebecca Williams.

Vanadium: the 'beautiful metal' that stores energy

Helena I. Gomes,  and Helen Abigail Baxter.
 
An unheralded metal could become a crucial part of the renewables revolution. Vanadium is used in new batteries which can store large amounts of energy almost indefinitely, perfect for remote wind or solar farms. And what’s more there is loads of the stuff simply lying around in industrial dumps.

Don’t let the dumpster diving put you off – never mind gold or silver, vanadium may just be the most beautiful metal of all. It’s the 22nd most abundant element in the Earth’s crust, though it’s rarely found naturally in its metallic form. Instead, vanadium can be found in more than 100 different minerals.

Colours of vanadium. Steffen Kristensen

Once extracted and dissolved in water, various forms of vanadium turn into bright, bold colours. It’s even named after “Vanadis”, the old Norse name for the Scandinavian goddess of beauty, Freyja.
Vanadium is not only beautiful, but also strong. Adding small percentages of it creates exceptionally light, tough and more resilient steel alloys. Henry Ford was the first to use it on an industrial scale, in the 1908 Model T car chassis, and today the vast majority of vanadium is used in structural steel, mainly to build bridges and buildings.

Vanadium flow batteries

The unique properties of vanadium make it ideal for a new type of batteries that may revolutionise energy systems in the near future – redox flow batteries.

Batteries store energy and generate electricity by a reaction between two different materials – typically solid zinc and manganese. In flow batteries, these materials are liquid and have different electric charges. Both are pumped into a “cell” where the electric current is generated. A tiny membrane separates the two liquids, so they are able to react but don’t come into direct contact.
Vanadium is used in these batteries as it can convert back and forth from its various different states, which can carry different positive charges. As only one material is used, the risk of cross contamination is eliminated. The liquids have an indefinite life, so the replacement costs are low and there are no waste disposal problems. Also, the battery is extended to a potentially infinite lifetime.

Vanadium flow batteries.

In flow batteries, the energy production and capacity are independent. Energy is stored in tanks, whereas the capacity depends only on the amount of liquid stored. This provides a great design flexibility that other batteries do not allow. They are also safer, as the two liquids don’t mix causing a sudden release of energy. Even President Obama is impressed.

The new energy reservoir

Vanadium flow batteries are too big and heavy to replace the lithium batteries found in your phone, however. These batteries are instead used for large stationary long-term energy storage, or to supply remote areas, or provide backup power. They’re the basis for a more efficient, reliable, and cleaner electrical energy market.

Energy storage is one of the main factors limiting the spread of renewables. When solar and wind power is produced at the wrong time of day we need to store it to use it during the evening demand peaks. Studies have shown that vanadium batteries can be a sustainable solution.

When we can create huge stores of energy to access as required, we will be liberated from the need to maintain rapidly-accessible energy generation such as coal or gas. Vanadium batteries can be a reservoir of energy much in the same way as we use actual reservoirs to store rainwater for later use.

Strengthened with vanadium. The Henry Ford / Life magazine

The ability to store electricity would reduce reliance on gas and coal. In turn this would increase fuel security and cut CO₂ emissions, helping to meet agreed emissions targets. No wonder then that the EU considers vanadium a critical metal for strategic energy technologies.

The hunt for vanadium

The metal is mined, and supplies are currently dominated by China, South Africa, Russia and the US. Vanadium has a medium risk of supply shortage and a high political risk.

However, as vanadium can be a byproduct of other sorts of mining, about 70% of the vanadium above ground is unused, left in industrial wastes such as mine tailings, debris or steel slags. In fact, a study I published with colleagues last year estimated that 43% of the annual global production of vanadium could be recovered from alkaline wastes, such as steel slag, red mud, fly ashes from coal energy production, and construction and demolition waste.

But there isn’t yet a firmly established technology to recover this vanadium. Certain bacteria and fungi can extract more vanadium from industrial wastes, and various solutions for turning this into useful metal are under development. But we still need to come up with a better way to reach potential sources of this beautiful metal.


Helena I. Gomes, Postdoctoral researcher in Environmental Sciences, University of Hull and Helen Abigail Baxter, Post Doc Research Assistant, Department of Geography Environment and Earth Sciences, University of Hull

This article was originally published on The Conversation. Read the original article.

Wealth in waste? Using industrial leftovers to offset climate emissions

Helena I. Gomes, Mike Rogerson, and Will Mayes.

More than a billion tonnes of potentially toxic, bleach-like waste is produced and piled in landfills every year, with often devastating effects. And yet most people haven’t even heard of these “alkaline wastes”.

We want to change this. Our research has identified nearly two billion tonnes of alkaline residues that are produced in the world each year, most of which can contaminate groundwater and rivers if not proper managed. We should be doing much more about the problem – these wastes can even be put to good use.

Alkaline waste can be solid or sludgy. It mostly involves slags, ashes or muds formed as a byproduct of steel, aluminium or coal power plants, waste incineration or the construction industry. All these wastes are different, but what they have in common is that they rapidly create bleach-like solutions when they meet rainwater.

Steel slag, a byproduct of the steel industry and an example of an alkaline residue.

Often it’s simply stored in piles or sent to landfill. This isn’t safe. The waste can form toxic dust that blows into the atmosphere, while rain that lands on top can filter through, picking up toxic chemicals and producing caustic “leachates” that can flow out into rivers and groundwater.

Steer well clear

Alkaline leachates have a toxic effect on aquatic life (we wouldn’t want to swim through bleach, either). It raises the water pH and metal concentrations, and consumes oxygen.

Carbonate precipitates in a small stream smothers aquatic habitats.

Once this stuff has been produced it’s hard to stop. Steel mills can be a source of alkaline leachates even 30 years or more after closure. Water with pH higher than 12 (somewhere between soapy water and bleach) has now leaked from one chromite waste tip for more than 100 years.

It’s hard to determine the exact link between contamination and problems for plants and animals, but alkaline waste can clearly cause harm. Studies have found ash from coal plants has killed geese and made tree swallows smaller and less fertile.

Perhaps the most severe case of alkaline waste poisoning happened in 2010, when a dam failed at an aluminium refinery in Ajka, Hungary. This released a million cubic metres of “red mud”, a byproduct of aluminium production with a pH level of around 13 in this case – similar to oven cleaner. The red mud inundated 1,000 acres of agricultural and urban land and was transported more than 120km down the Marcal river to the Danube, “extinguishing” all life in the tributary. The flood drowned ten people and left many more with severe chemical burns.

Can we make it stop?

We can treat alkaline leachates through aeration or by adding acid to neutralise it but this is expensive. We need sustainable alternatives. One promising proposal involves constructing wetlands in and around polluted sites, where the marshy ground, the plants and the associated microorganisms restrict the contamination.

Many attempts have been made to find ways of reusing these wastes but none of them are practical enough to stop landfill disposal. Alkaline wastes have been used in road construction, concrete, cement and plasterboard, for example.

Adding these wastes to the soil can reduce acidity, so usage as phosphate fertiliser is also common, while labs are testing whether it can be used in wastewater treatment.

All right junk in all the right places?

It can even help the fight against climate change. Chemicals in the wastes such as calcium and magnesium react with carbon dioxide and remove it from the atmosphere, storing it as a stable mineral. This form of carbon sequestration essentially mimics natural weathering processes and could be a safe and permanent storage option since only acid or extreme temperatures of 900°C or more can release this CO₂. It could even help offset some of the emissions from the energy-intensive industries that create alkaline wastes in the first place.

In fact, if all materials that contain silica (cement, construction and demolition wastes, slag, ash and combustion products) were used for sequestration they could take 697-1,218 megatonnes of CO₂ out of the atmosphere each year.

Steel slags alone could capture 170 megatonnes per year, while the red mud stored worldwide could capture 572 megatonnes. If all the red mud produced in a year was carbonated, 3–4% of the aluminium industry’s global CO₂ emissions could be captured.

Red mud has already sequestered 100 megatonnes of CO₂ worldwide from the late 19th century to 2008 – without the industry even trying. Boosting this number could allow for some real downward pressure on its emissions.

Maybe it’s time to get clever

Recent studies have shown alkaline wastes also contain large quantities of metals we would like to recover for recycling. Some are critical in terms of supply, or essential to new green technologies. For example vanadium, used in offshore wind turbines, lithium and cobalt for vehicle fuel cells, and rare earth elements crucial for solar power systems.

The obvious solution: try to unify the needs of resource recovery and remediation, by developing treatment methods for alkaline leachates that recover critical elements soluble at high pH, suppress dust production, increase carbon sequestration and treat the pollution caused.

With thanks to our study co-authors Douglas Stewart, professor of geo-environmental engineering, and Ian Burke, associate professor of environmental geochemistry, both at the University of Leeds.

To learn more about the Alkaline Remediation project, visit the website: https://alkalineremediation.wordpress.com/ 
 

Helena I. Gomes, Postdoctoral researcher in Environmental Sciences, University of Hull; Mike Rogerson, Senior Lecturer in Earth System Science, University of Hull, and Will Mayes, Senior Lecturer in Environmental Science, University of Hull

 
This article was originally published on The Conversation. Read the original article.

Green building as urban sustainability strategy

by Julia Affolderbach
 
The building sector has been identified as the single largest contributor to human-related greenhouse gas emissions. At the same time, the sector is also seen to hold the greatest potential to lower emissions based on the relatively low levels of retrofitting existing or constructing new buildings, the availability of technologies, and the need to transition towards greener energy supply and demand (see for example related earlier blogs on sustainable building and green homes). The GreenRegio research project focuses on the potential of reducing greenhouse emissions through changes in the building sector (i.e. implementing more sustainable building practices) as urban climate change mitigation strategy. Based on case studies in four city regions – Freiburg, Luxembourg, Vancouver and Brisbane – one of the main objectives of the project is to identify the reasons behind innovations in green building.

Information sign on a 'Green Building Audio Tour' offered by the City of Vancouver in its award-winning Southeast False Creek neighbourhood.

One perspective we have adopted as part of our research is to understand green building through urban sustainability policies that seek to respond to climate change but also include aspects of city branding and marketing as part of broader, global and competitive sustainability discourses. Using the City of Vancouver’s “Greenest City 2020 Action Plan” (GCAP) and based on document analysis and interviews, we seek to assess the role of the GCAP as part of the city’s sustainability transition, and how green visioning and marketing can contribute or divert from the Plan’s objectives.

Greenest city Vancouver? Vancouver's beautiful natural setting between mountains and ocean is used as one of the main arguments to explain the strong environmental commitment within the local community.

Vancouver’s Greenest City 2020 Action Plan is a politically motivated strategy with the ambitious goal to turn Vancouver into a world leading green city. It consists of 10 goals that are further defined through identified mid-term (2020) and long-term (2050) targets to be monitored through measurable indicators specific to each of the targets. The GCAP illustrates how green policies are used to both draw on and speak to local constituencies, as well as a global audience by framing the ‘green city’ both as a local process and globally competitive positioning.

The competitive nature of the policy and the ambition to present the city as global leader in sustainability is already evident in the development of the GCAP. The development of the strategy was led by a ‘blue ribbon task force’, the Greenest City Action Team (GCAT), consisting of leading and well-known academics, civic and environmental leaders and industry representatives, which commenced work in Feb. 2009 and delivered its recommendations later that year. The GCAT identified ten sustainability goals based mainly on an evaluation of best policies and best practices used in leading green cities around the world which are grouped into three areas: zero carbon, zero waste and healthy ecosystems. Nine of the goals were chosen based on what other cities were doing internationally while the tenth goal, local food, was at the time identified as unique to Vancouver. Interestingly, the goal to ‘out-green’ other cities was identified as a clear motivation in our interviews with respondents who are or had been involved in the implementation of the GCAP.

At the same time, the GCAP incorporated views and interests of residents and the general public, both through public engagement and participation during the development of the strategy and the implementation of the objectives. Targets involving green jobs, transportation infrastructure and increased citizen involvement resonate with local people  and emphasize municipal empowerment, while at the same time they seek to address a global audience through a language of superlatives.

A model laneway house developed to illustrate low-carbon building solutions as well as urban densification. Laneway houses are small homes that are added to pre-existing lots (usually in the backyard and opening to the back lane) that help increase density in low-density neighbourhoods without changing the existing building structure.

The focus on global positioning and leadership can be criticized for using local sustainability issues in urban marketing and branding strategies in order to advertise the city as attractive place for tourists, workers, and businesses alike. At the same time, the pursuit of global leadership can offer a number of positive effects beyond green washing. For example, our interview partners described how the ambitious goals set within the GCAP have provided precedent cases that have been used by other municipalities to implement new regulations. One other benefit relates to the provision and sharing of specific know-how, data, experience and establishment of collateral knowledge networks and opportunities for co-learning. To illustrate the point, the City of Vancouver offered a two-day workshop in May 2015 to share its experience and give practical advice to other cities on how to set up a sustainability centre based on Vancouver’s CityStudio. CityStudio is a city-led innovation hub that brings together city staff, university students, and community members to create, design, and implement community projects of all kind in support of the GCAP. The ‘art of cities’ workshop brought together teams from 8 Canadian cities that are working on building up similar initiatives to engage students and citizens in solutions to sustainability issues in their local communities.

Vancouver CityStudio's Keys to the Streets project that seeks to promote the use of public space and increase the sense of community. (Photo: Inside Vancouver)

GreenRegio is a 3-year research project funded by the National Research Fund Luxembourg and the German Research Foundation. Further information on the project and research findings from Freiburg, Luxembourg, Brisbane, and Vancouver are available on the project website.

Freecycle - blurring the analyses of consumption

Guest blog by Sally Eden

Ever eBayed, Freecycled or Shpocked something that you owned but no longer needed? Millions of us have and the fact that the names of these websites/groups are now verbs indicates how common digital practices of selling or exchanging used goods online have become between consumers. I have been giving away and receiving consumer items for free through two of my local Freecycle groups for some years in my spare time. But after twenty years, on and off, of analysing sustainable consumption professionally, I grew more intrigued by whether there was more to Freecycling than avoiding landfill by passing stuff on to others, instead of taking it to the dump (as some Freecyclers like to describe what they do) and wrote a paper about it, which has now been published in the Journal of Consumer Culture.

Why analyse Freecycle? First, Freecyclers do a lot of ‘moral ordering’ in support of sustainable and ethical consumption. That is, their online posts re-value items, changing them from something unwanted by the owner to something useful for someone else. Someone might offer broken paving slabs for crazy paving, used bricks to make someone else a BBQ or even an old washing machine door taken not as a replacement part, but to make a dome-like window in a garden fence so that the new owner’s dog could peek out and see the world, a free alternative to the ‘PetPeek’ window sold online - thanks to Richard Lamin for telling me about that! Freecycling practices thus reimagine and reproduce both products and consumers in sometimes surprising ways.

Freecycling also exposes the problems with three common ‘binaries’ (that is, two-fold oppositions or assumptions) that underlie many analyses of consumption. First is the assumption that consumption is separate from production, whereas in Freecycling, the consumer also offers and describes items online, becoming a sort of producer and retailer. This is even more obvious when spare plants or food from an allotment glut is offered. George Ritzer and others have written about the blurring of consumption with production as ‘prosumption’ – to emphasise that these different practices cannot be easily teased apart – and examples also include a consumer reviewing a book that they have read on a retailer’s website that helps the retailer to sell more books or a consumer who blogs about cosmetic products on YouTube supported by commercial adverts.

Second, Freecycling merges digital and material practices. Often we hear about the rise of online consumption crushing the High Street and other ‘brick and mortar’ stores, but in reality these different spaces are linked. Freecycling uses online systems to connect offerer and receiver, but they usually meet in person to exchange the physical item, similar to the way that some stores now offer ‘Click and Collect’ mode for buying online but collecting in person. In other cases, people ‘window shop’ in bricks-and-mortar stores to choose an item by looking and perhaps trying it on, but ‘Windows shop’ online to compare prices and finally buy it – in some cases, Freecycling offers people the opportunity to try out a product (a breadmaker, a children’s slide) for free but perhaps in a well-used and rather battered form, before deciding to buy themselves one in mint condition.  

Third, Freecycling blurs what is often referred to as ‘alternative’ consumption with the mainstream. Some Freecyclers may feel that they are challenging the wastefulness and built-in obsolescence of mainstream consumer society, but others use Freecycle to ask precisely for desirable consumer items or, when offering them, use hotlinks to chainstore retailers to show what the product looks like when new (and often its original cost) as part of making it look attractive to potential collectors. Freecyclers still draw on the mainstream repertoire of modern consumption, even while aiming to counter the problems they perceive it produces.

For all these reasons, Freecycling shows us how consumption is more blurred, less analytically clean and more circular than is often appreciated. Consumption blurs into production, digital into material, alternative into mainstream, with diverse practices continually being reinvented as well. And it is fun. Now, who would like the tricycle that my son has now grown out of? And who is offering a bike that he might like? 

Eden, S., 2015. Blurring the boundaries: Prosumption, circularity and online sustainable consumption through Freecycle. Journal of Consumer Culture. 0(0) 1-21. DOI: 10.1177/1469540515586871

Reconstructing Bronze Age environments at Hobbister, Orkney

by Michelle Farrell (@DrM_Farrell)

Last Monday (2^nd February) it was World Wetlands Day, and consequently my Twitter feed was full of stunning photographs of different types of wetland. Much was made of their role in alleviating flooding by acting as giant natural sponges which soak up water, as well as their biodiversity value and ability to store vast amounts of carbon. But despite all the wetland appreciation that I witnessed on Monday, there was very little mention of their importance to archaeologists and palaeoecologists.

Wetlands have a whole archaeological sub-discipline devoted to them. Wetland archaeologists are drawn to these damp, muddy environments because the waterlogged, anaerobic conditions inhibit microbial activity and often result in exceptional preservation of artefacts made from organic materials such as plant fibres, hair, wood and leather. These artefacts rarely survive on dryland sites, meaning that wetlands often preserve an additional level of detail relating to the everyday lives of our ancestors. Wetland archaeological sites also preserve plant and insect remains, which give us insights into the function and economy of the sites. Additionally, wetlands contain an archive of information relating to their own environmental history. Past changes in vegetation can be reconstructed from pollen grains, and the remains of single-celled organisms called testate amoebae provide information about past climates.

Wetlands were also important to people in the past. Across north-west Europe, deposits of precious metalwork were made in both wetland and dryland environments during the Bronze and Iron Ages. Artefacts deposited on dryland tend to be interpreted as valuables that were either lost or hidden with the intention of retrieving them in the future. Given that it would have been difficult to retrieve items from wetlands once they had been deposited, these objects are commonly thought to be votive offerings. In the past wetlands may have been viewed as wilderness and as being resistant to domestication, and it may be that these deposits represent an attempt to appease supernatural powers associated with these environments during times of perceptible environmental change. There is considerable palaeoenvironmental evidence for a shift to a wetter climate during the Bronze Age, particularly in upland regions of Britain. Deposition of valuable metalwork was perhaps an attempt to domesticate and control the changing landscape during this period of wetter climatic conditions.

To date, evaluation of this hypothesis has been hampered by a lack of palaeoenvironmental data relating to the findspots of votive deposits - and in many cases, the exact locations of the finds are not recorded. In Orkney in 2006, when I had just begun my PhD research with the aim of reconstructing Bronze Age vegetation and environmental conditions in the islands, peat cutters at Hobbister in Orphir uncovered a beautiful example of a late Bronze Age socketed axehead. Was it a votive deposit, and was there any palaeoenvironmental evidence for changing conditions at the time of deposition? An archaeological survey of the site had revealed various structures interpreted as the remains of a prehistoric field system, as well as several probable Bronze Age burial mounds. The discovery of a potential Bronze Age landscape buried by peat meant that the site would be useful for my PhD research, even if it turned out that I wasn’t able to say much about possible reasons for the axehead deposit.

 

Blanket bog at Hobbister, Orkney

Commercial peat extraction at Hobbister, Orkney

I analysed two peat cores from the site – one from the deepest area of deposits to ensure the fullest possible record was recovered, and one from as close as possible to where the axe was found. Analysis of the peats revealed evidence for a mixed economy based on arable cultivation and livestock rearing. The field system probably formed part of an ‘infield-outfield’ system, where fields nearest to a settlement (‘infields’) were cultivated more or less continuously by adding fertiliser in the form of dung, turf and seaweed, while those beyond (‘outfields’) were only cultivated on a temporary basis, being manured only through the folding of livestock in the summer prior to cultivation. Beyond the outfields would have been common pasture for livestock grazing. At Hobbister the pollen evidence indicates that this would have largely consisted of heathland, and there is evidence from charcoal contained within the peat that this was managed by burning to improve the quality of the grazing by encouraging dense growth of new shoots of heather, which contain more nutrients than old-growth heather, and by allowing grasses to grow in the gaps created by fire.

The remains of plants preserved in the peat at Hobbister suggest that the surface of the bog became slightly wetter during the later Bronze Age, at around 1200-800 BC. If the bog became wetter at this time, it is likely that the surrounding area did too. The suitability of land for farming would have been highly dependent on local hydrology, and increased wetness may have rendered the soil incapable of supporting cereal crops. Although the pollen evidence suggests that cereal cultivation at Hobbister continued at least until the Iron Age, local people would have been extremely aware of the gradual encroachment of peat onto formerly more productive land, and it is distinctly possible that they tried to halt these changes through votive deposition.

Distinctions have been drawn between votive deposits made in different types of wetland, with the suggestion that rivers, with their opposing banks, may have been viewed as boundaries dividing communities, and that deposition here might have been a display of power and prestige to other social groups. Bogs, on the other hand, may have been the focus for ritual acts aimed at reinforcing social cohesion within communities (Fontijn 2002; Mullin 2012). Orkney has no major river systems, but the highly indented coastline may have played a similar role in dividing communities here. Hence the deposition of the Hobbister axe could be seen as an attempt by local people to maintain community integrity during a time of perceptible environmental change.

In summary, wetlands are awesome - they preserve so much information about our past that simply doesn't survive on dryland archaeological sites. Next year on World Wetlands Day, we palaeoecologists and archaeologists need to get in on the act and promote the value of wetlands for understanding our heritage!


References:
Fontijn, D.R. (2002) Sacrificial landscapes: cultural biographies of persons, objects and ‘natural’ places in the Bronze Age of the southern Netherlands, c. 2300-600 BC. Analecta Praehistorica Leidensia 33/34: 1-392 (download for free here)

Mullin, D. (2012) The river has never divided us: Bronze Age metalwork deposition in western Britain. Oxford Journal of Archaeology 31: 47-57

This post is based on my recent paper, available here:

Farrell, M. (in press 2014) Later prehistoric vegetation dynamics and Bronze Age agriculture at Hobbister, Orkney, Scotland. Vegetation History and Archaeobotany. doi: 10.1007/s00334-014-0507-6

International Student Mobility: The Role of Social Networks

By Suzanne Beech (@suzanneebeech)

I have a new paper online early with Social and Cultural Geography, it is the second to come out of my PhD thesis on international higher education and the factors which influence students in their decision to study abroad. This paper focuses on one of the biggest factors effecting student mobility (and many other forms of mobility as well) - the role of social networks of friendship and kinship. It looks at the experience of 38 international students studying at three UK universities who were either interviewed or took part in a small focus group between March 2011 and February 2012. Each of the students that took part was enrolled on a diploma seeking programme of study (i.e. their period of time overseas was for the duration of their degree, rather than related to a temporary exchange or sojourn abroad). They came from 23 different countries and were studying both at undergraduate and postgraduate level. While I did not explicitly ask them about their socio-economic background it is likely that, given higher education mobility is often a very expensive pursuit, they came from relatively well-off backgrounds.  What was common to every one of the students that took part was the centrality of their friends and family in making their decision, their social networks were key to their mobility.

1.        What is a social network?

Social networks in this context are not limited to online social networks like Facebook and Twitter. The social networks in which my research is interested are much broader than this. At the most basic level they represent the multiple people (or actors) that a person communicates and interacts with in their day-to-day lives sharing resources and information in the process. Your social network is therefore anyone who you know well enough to engage in conversation, even if that conversation takes place along very limited lines. Any one person can, therefore, have hundreds of people in their social networks and can be part of numerous (sometimes overlapping) social networks e.g. your family could be one social network, your work colleagues another, the people in your tutorial group another and so on. International students, like everyone else, are part of complex networks of individuals all sharing information with one another. John Urry (2007; 2003) has written about how these networks shape mobility by creating connections between people through which they are able to share their experiences of being mobile. Members of a network are therefore able to tell others of the benefits of engaging in mobility and how to become more mobile themselves. It is therefore through networks that mobility often takes place.

2.       How do social networks influence mobility amongst international students?

My research shows that social networks operate in two ways in relation to international students. First, they can offer explicit advice and encouragement. This is perhaps less common than you may think, certainly most students did not admit to seeking out advice and encouragement – perhaps because international student mobility is often considered (at least socially) an individual activity where you go out and forge your own lifecourse – but there was evidence of some students actively turning to others for advice. Aimee from Canada for example spoke to people in her field about the value of an overseas degree, Subash and Sachin (from India) both turned to Facebook to find people who had also studied their course in the UK and Lily (from Malaysia) talked about the importance of being able to discuss her course with current students when on an open day.

    

More common, however, was the concept that social networks were about sharing the lived experiences of overseas mobility. In this context their social networks did not so much offer them advice and encouragement instead they began to normalise the process of going overseas. Asan (from Nepal) discussed how in his school it was normal for almost everyone to study abroad, suggesting a huge “95 per cent” went overseas (this is possibly an exaggeration, but whether literal or not it is clear that lots of people chose to do so). Marianna (from Greece) wanted to have the same experiences that a friend had when she studied in the UK. Hazel (from the USA) watched friends go backpacking in Europe and wanted to have a similar experience. As Urry (2007) suggests, they had built a greater awareness of travel which had normalised engaging in long term mobility, leading to point 3…

3.     Social networks establish cultures of mobility.

What is interesting is that these networks become self-perpetuating to an extent. More people study overseas and share their experience (either explicitly or implicitly) with their social networks. This then introduces more people to the idea of studying abroad, some of whom will explore the option and choose to study outside of their home country, who will then share their experience with their social networks and so on, and so on, and so on, and so on, and so on, and so on. It effectively establishes a culture of mobility amongst international students which normalises the process of studying overseas.

There was evidence of the importance of social networks amongst every student who took part in the interviews and focus groups for my research. This suggests that these relationships are critical to mobility. It did not seem to matter where the students came from, or their level of study, social networks were somehow active in all of their decisions’ to study overseas. They had created cultures of mobility for these students which had normalised the process of studying overseas.

My paper on International Student Mobility: The Role of Social Networks is currently online early with Social and Cultural Geography and is available for download here.

References

Urry, J. (2003). Social networks, travel and talk. British Journal of Sociology, 54, 155–175.

Urry, J. (2007). Mobilities. Polity Press: Cambridge.

Kinematic indicators in the Green Tuff Ignimbrite: can they tell us about the timing of caldera collapse?

By Dr Rebecca Williams (@volcanologist) & Jodie Dyble

In the summer of 2014 I have had a Nuffield Foundation student, Jodie, working with me towards a Gold CREST Award, which we blogged about the other week. Here, I’m going to talk a bit about the research she did.

Jodie looked at the Green Tuff Ignimbrite on the island of Pantelleria, Italy. The Green Tuff Ignimbrite is a rheomorphic ignimbrite which was emplaced during an eruption about 45 thousand years ago. An ignimbrite is the deposit from a pyroclastic density current. Rheomorphic means that the deposit was still hot when it was formed, so that the shards of ash welded together and was able to be deformed ductiley. Rheomorphic ignimbrites are common on places like Gran Canaria, in the Canary Islands (where the classic work of Schmincke & Swanson 1967 was done) and the Snake River Plain in the western US. You can get two types of rheomorphism, that which occurs during deposition of the ignimbrite (e.g. the overriding current exerts a shear on the underlying deposit) and rheomorphism which occurs after the deposit has been fully formed (e.g. the deposit starts slumping under gravity). I’m avoiding using primary vs secondary here, as actually the historical meaning of those words and their relative timings can be difficult to disentangle. For a very good, concise overview take a read of (Andrews & Branney 2005). Either way, rheomorphic structures within the deposit like lineations, folds, tension gashes and rotated crystals or clasts, can tell us about this sense of movement. Volcanologists interpret these kinematic indicators in the same way a structural geologist would interpret verging folds, or rotated porphyroclasts in a mylonite (e.g. Passchier & Simpson 1986). You can even determine the direction a pyroclastic density current flowed if you map out these kinematic indicators across the ignimbrite (e.g. Andrews & Branney, 2011).

Schematic diagram of the development of rheomorphic structures in a syndepositional shear zone during the deposition of an ignimbrite. Taken from Andrews & Branney, 2005.

The Green Tuff eruption was said to have been a caldera forming eruption, but the details of this have been debated. Two different calderas have been proposed: the Cinque Denti caldera (Mahood & Hildreth 1986) and the Monastero caldera (Cornette et al. 1983; Civetta et al. 1988). These share the same scarps to the east, west and south but while the Cinque Denti caldera has exposed scarps in the north (the Costa di Zinedi scarp, the Kattibucale scarp and the Cinque Denti scarp), the Monastero caldera has a buried northern scarp. During my PhD on the Green Tuff (Williams 2010; Williams et al. 2014) I found that the Costa di Zinedi scarps, the Kattibucale scarps and the Cinque Denti scarps were extensively draped by the Green Tuff, right down to the bottom of the exposed caldera walls.

The map shows the two different proposed calderas for the Green Tuff eruption. Panoramics and sketches show the draping Green Tuff down the three disputed scarps. Localities used in this study are highlighted. From Williams, 2010.

What Jodie set out to determine this summer was when that draping occurred. My work on the chemical stratigraphy of the Green Tuff already determined that those drapes represented the earliest part of the eruption. So, did caldera collapse happen after the deposition of the Green Tuff and did those drapes represent the rheomorphic slumping of the deposit down a newly formed caldera wall? Or, did the caldera wall exist before the emplacement of the Green Tuff, and those drapes represent a deposit formed by an overriding current? In the field, macro indicators (such as large scale folds) suggested that the deposit slumped down the caldera wall. We went in search of micro kinematic indicators to see if they would tell the same story.

 Some of the micro-kinematic indicators seen in the thin sections from the Green Tuff Ignimbrite, including verging folds and rotated clasts (δ and σ–objects). From Dyble & Williams, 2015.

What Jodie found was compelling evidence for upslope flow in the thin sections that she analysed. Thus, those deposits were formed by the Green Tuff pyroclastic density current flowing up the caldera scarps, depositing and shearing the underlying deposit as it went. Which means that those caldera scarps must have existed before the Green Tuff ignimbrite did, so we support the idea that those scarps had nothing to do with the Green Tuff eruption. We think that’s pretty neat and we’re presenting the work at the Volcanic and Magmatic Studies Group annual conference, which in January 2015 will be held in Norwich. Jodie has already made the poster we’ll be presenting as part of the assessment required to achieve a Gold CREST Award, so we’ve decided to publish that online before the conference. I’d like to thank Jodie for some stellar research this summer, despite only having done 1 year of Sixth Form (AS level) geology (she’s 17!), and answering some questions I’ve been pondering for about 6 years. Hopefully, this data will go into a couple of papers I’m working on too!

Andrews, G. & Branney, M., 2005. Folds, fabrics, and kinematic criteria in rheomorphic ignimbrites of the Snake River Plain, Idaho: Insights into emplacement and flow. In J. Pederson & C. . Dehler, eds. Interior Western United States: Field Guide 6. Bouldor, Colorado: Geological Society of America, pp. 311–327.

Andrews, G.D.M. & Branney, M.J., 2011. Emplacement and rheomorphic deformation of a large, lava-like rhyolitic ignimbrite: Grey’s Landing, southern Idaho. Geological Society of America Bulletin, 123(3-4), pp.725–743.

Civetta, L. et al., 1988. The eruptive history of Pantelleria (Sicily Channel) in the last 50 ka. Bulletin of Volcanology, 50, pp.47–57.

Cornette, Y. et al., 1983. Recent volcanic history of pantelleria: A new interpretation. Journal of Volcanology and Geothermal Research, 17(1-4), pp.361–373.

Dyble, J.A., Williams, R., 2015. Micro kinematic indicators in the Green Tuff Ignimbrite: can they tell us about caldera collapse? VMSG Meeting, Norwich, 5th-7th January 2015. http://dx.doi.org/10.6084/m9.figshare.1160476

Mahood, G. & Hildreth, W., 1986. Geology of the peralkaline volcano at Pantelleria, Strait of Sicily. Bulletin of Volcanology, 48, pp.143–172.

Passchier, C. & Simpson, C., 1986. Porphyroclast systems as kinematic indicators. Journal of Structural Geology, 8(8), pp.831–843.

Schmincke, H. & Swanson, D., 1967. Laminar viscous flowage structures in ash-flow tuffs from Gran Canaria, Canary Islands. The Journal of Geology, 75(6), pp.641–644.

Williams, R., 2010. Emplacement of radial pyroclastic density currents over irregular topography: The chemically-zoned, low aspect-ratio Green Tuff ignimbrite, Pantelleria, Italy. University of Leicester. http://dx.doi.org/10.6084/m9.figshare.789054
Williams, R., Branney, M.J. & Barry, T.L., 2014. Temporal and spatial evolution of a waxing then waning catastrophic density current revealed by chemical mapping. Geology, 42(2), pp.107–110.

Why Place Matters: Imaginative Geography and International Student Mobility (My Area Paper)

By Suzanne E. Beech (@suzanneebeech)

A little background…

Over the last ten years (or so) lots of research has looked into why students choose to come to the UK (or go elsewhere), including my own. This isn’t surprising as international students represent a key part of our student body in the UK. In fact during 2012/13 just under 20% of the students studying in UK institutions were non-UK domiciled (i.e. they did not hold a UK passport) (check out the HESA website for more information). International students are important for lots of different reasons but often research has tended to focus on the economic benefits. This isn’t surprising either, in the UK international students from outside of the EU can pay over £30,000 a year in fees (depending on where they study) and can therefore be an important financial support for some universities. However, this is only part of the picture as they can also make significant contributions to the wider economy, in 2012 the University of Exeter, together with Oxford Economics published a report which suggested that the 5,000 international students at the University of Exeter supported some 3,280 jobs throughout the South West of England (see here).

However, it is important to recognise that international students are not only important financially, they are also important culturally. We live in a world where the job market is no longer local, it’s global – so it’s really important that students leave university with an understanding of how to communicate with people from a range of different social and cultural backgrounds, international students provide a way of bridging some of these cross-cultural divides (in an ideal world). All of this means that universities (and you) have a vested interest in supporting the international student community here in Hull or wherever you are!

Imaginative Geographies and International Students

My work has tended to look at the motivations for overseas study and I have recently published a paper in Area on how international students use different imaginative geographies to decide where to study. In a nutshell these imaginative geographies come out of the perceived power relations between two nations. The term was originally proposed by Edward Said in his seminal work of 1978 Orientalism (well worth a read) in which he demonstrated how the West created an imagined, exotic East and how these perceptions spread through literature and art, as well as stories from those who had travelled to these foreign destinations and so on. We still have imaginative geographies today, and they don’t just have to be in terms of the West looking on the East, but rather anything that compares the familiar (‘Ours’) with the unfamiliar (‘Theirs’ or ‘the Other’). Think about it - we are constantly bombarded with information about the ‘Other’ – friends’ holiday photos on Facebook, television programmes which allow us to ‘experience’ somewhere else, books, travel brochures, the incredible wealth of information we can find on the Internet – all without even leaving your home.

So what (imaginative) geographies do we like to send out to our potential international students? The British Council and Education UK are responsible for promoting the UK to prospective international students and on the 28^th September 2012 they published this YouTube video entitled ‘The Adventure of a Lifetime’. 

It follows a typical, female international student who is 'hard-working', 'friendly', 'intelligent' and 'fun-loving' from her arrival in the UK until graduation and all of the experiences she has along the way. It portrays the UK as exciting and diverse, a place where you will get a top-class education, but also have fun along the way. In my opinion one of the most interesting things about the video is the lack of differentiation between different regions in the UK. The British Council is usually good at this, but that doesn’t seem to be the case here. The video also does something else that is very important in terms of international students’ imaginative geographies – it reiterates the ideals of academic imperialism. The UK is the place to study.

There are lots of different aspects to imaginative geography, but three in particular matter when it comes to international students:  ideas of power and postcolonialism (academic imperialism comes in here); the importance of community and shared imaginative geographies; and the evidence that imaginative geographies are not necessarily accurate they are, after all, ‘imagined’. To give you an example I will introduce you to one of my research participants, Rafiah (not her real name). She came from Trinidad and Tobago and had chosen to study in Nottingham, she was about 20 when we first met. Rafiah commented that coming from Trinidad and Tobago the UK  had seemed almost “magical”, she felt that people at home sometimes had a bit of an “inferiority complex” and that there is often a real desire to study and live somewhere else. This did not mean that Rafiah did not like her home country, but rather that her schooling, education, upbringing, and so on had encouraged her to think of studying overseas as an important alternative to studying at home. This was something that was common in her home-country, she told me that when people got the opportunity to study overseas they almost always decided to pursue it. So, here we can see how this is reflecting in part those (post)colonial ideals (the UK is better than home) and also how this is also a shared or community process (everyone who can does it). 

However this is really only part of the story, what also matters is whether all those years of dreaming lived up to the reality. Well, Rafiah was more than a little surprised when she arrived in Nottingham – the city was not as she thought it would be. This is not unusual, many international students won’t have visited their universities before they arrive and they can be shocked when they get here. Rafiah had visited London, but she had never been to Nottingham before, and she was taken aback at how different it was to the hustle and bustle that she had experienced in the capital. In fact she had believed that Nottingham would be very like London in some ways, she was a bit disappointed almost that it was a “quiet little place”. This is just one person out of the many that I spoke to, all of them had similar stories to tell – dreaming and imagining their experience was a key part of becoming an international student.

So why does this matter for us? Well, as I mentioned at the beginning, international students are a really important part of our student body. They are a financial asset to the UK’s universities but equally they are a cultural asset as well. It’s important to understand how and why they choose to study overseas and to consider what makes us an attractive destination. So where should our research go from here? I’m currently considering some new research directions, away from international students themselves and towards those who do the recruiting. Understanding how universities and the UK promote themselves will provide greater insights into how they mobilise imaginative geography when selling the ‘place’ of the university. And what about you? Well, research has suggested that contact between international and local or host students is often limited – if you are studying or working ‘at home’ why not try to make some extra efforts to befriend someone from overseas and get to know a bit more of their story.


You can find a link to my paper here:

Beech, S.E. (2014) "Why Place Matters: Imaginative Geography and International Student Mobility" Area, 46(2):170-177.