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Research seminars

Both external and internal speakers are invited to the School of Geography, Geology and the Environment to present the latest results of their research. All seminars will be accessible on Microsoft Teams until further notice. On joining the meeting please ensure that your microphone and camera are off, if you wish to ask a question please use the raise hand function or send your questions in advance. Everyone is invited, so please join us!

The Spatial Demography of Depopulation: The U.S. Example

Wednesday 13 January 2021, 1.00pm

Professor Rachel Franklin, Newcastle University

Although the United States continues to experience robust population growth overall, increases have for years been unevenly distributed across regions, counties, cities, and neighbourhoods. Those areas with ongoing population loss face a range of challenges, from demographic to economic to health-related.

In this talk we propose a typology of population loss for counties in the United States that can serve to assist policymakers and researchers in identifying vulnerable locations and populations. Our primary proposition is that context matters: along with amount of loss, our classification incorporates measures of both temporal and spatial context. Together these elements differentiate between, for example, counties in growing regions that are experiencing only recent population loss and those for which decline has been persistent over time. We employ contemporary (2000–2010) and historical (1950–2000) county-level population data for the United States to quantify and characterize the areal extent of population decline and to explore demographic characteristics for different types of areas identified in the analysis.

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Investigating mantle geochemistry and volatile cycles by combining geochemistry with geodynamical models of mantle convection

Friday 15 January 2021, 1.00pm

Dr Rosie Jones, University of Oxford

Noble gas compositions (e.g., 3He/4He, [40Ar]) obtained from mid-ocean ridge and ocean island basalts (MORB and OIB) have been used as fundamental lines of evidence for a long-lived, volatile rich reservoir in the deep mantle. However, this is at odds with multiple lines of evidence from geochemistry (e.g., radiogenic isotope systems such as U-Th-Pb, Lu-Hf, and Sm-Nd) and geophysics (e.g., seismic tomography) suggesting that the lower mantle contains recycled crustal material. In this study, a combined geochemical-geodynamical approach is used to investigate: (1) the dichotomy between primordial and recycled components in the mantle; and (2) how the noble gas compositions of the MORB and OIB mantle sources, as well as the crust and atmosphere, are generated.

These questions are addressed by integrating U-Th-He and K-Ar isotope systematics into a geodynamic model of mantle convection, which incorporates Earth-like phase and viscosity structure. Such models have previously been shown to reproduce mantle geochemical distributions (e.g., DMM, HIMU and EMI compositions) for multiple isotope systems (U-Th-Pb, Rb-Sr, Sm-Nd, Re-Os, and Lu-Hf) (Brandenburg et al., 2008; Jones et al., 2019). Several hypotheses are tested in this latest modelling study, including: the subduction and storage of dense eclogite in the deep mantle; the outgassing of 3He from the Earth’s core; the early subduction of extra-terrestrial material; and the recycling of seawater-derived Ar. Model sensitivities are explored and the model results are compared to observed noble gas concentrations and isotopic compositions obtained for MORB, OIB, and the atmosphere.

References:

Jones, R.E., van Keken, P.E., Hauri, E.H., Tucker, J.M., Vervoort, J. and Ballentine, C.J., 2019. Origins of the terrestrial Hf-Nd mantle array: evidence from a combined geodynamical-geochemical approach. Earth and Planetary Science Letters, 518, pp.26-39.

Brandenburg, J.P., Hauri, E.H., van Keken, P.E. and Ballentine, C.J., 2008. A multiple-system study of the geochemical evolution of the mantle with force-balanced plates and thermochemical effects. Earth and Planetary Science Letters, 276(1-2), pp.1-13.

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Footprints are not feet: Interpreting dinosaur footprints mechanistically

Thursday 21 January 2021, 1.00pm

Dr Peter Falkingham, Liverpool John Moores University

Fossil footprints offer a view on extinct life complimentary to that presented by bones and skeletons. Made during an animal’s life, footprints can record behaviour, soft tissue, and biomechanics in a way that the remains of a dead animal cannot. But the physical formation of a footprint – the dynamic interaction of a deforming foot and compliant substrate – do not result in a 1-1 relationship between footprints and feet. Exploring how footprints form can help us reverse engineer track formation and learn more about extinct animals.

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How (and why) does the environmental state fail?

Wednesday 27 January 2021, 4.00pm

Dr Jessica Dempsey, University of British Columbia and Dr Rosemary Collard, Simon Fraser University, Canada

Nature’s devaluation – its treatment as cheap, or disposable – is a key strategy of capitalist accumulation. This point is by now axiomatic within critical environmental scholarship. But how exactly is nature devalued? What institutions and mechanisms deliver cheap natures? And especially, how is cheap nature maintained within increasingly “environmental states” – that is, states with ostensibly protective environmental laws and regulations? Towards an answer, we look to woodland caribou in Canada, a species undergoing runaway defaunation in an era of expanding formal protections. Scientists are clear that woodland caribou declines stem from proliferating industrial development: mines, forestry, and oil and gas activities and infrastructures. All these developments must be approved by the state, which is also responsible for protecting and recovering caribou, a designated species at risk in Canada. So how does this environmental state keep caribou cheap? Partial answers can be found in state and financial records. A forensic analysis of coal mining approvals and financial flows in endangered Central Mountain Caribou habitat in British Columbia reveals three ways the state devalues caribou in service of capital accumulation. First, the state subsidizes developments like mining that destroy caribou habitat. Second, the state allows companies to “idle” their mines when coal prices drop, prolonging the period of caribou habitat disturbance. And finally, the state justifies its approval of these mines based on promised social benefits, like taxes, but these benefits are rarely delivered. In these ways, the state delivers cheap caribou and facilitates capital accumulation for the (few) beneficiaries of caribou decline: namely, company owners and shareholders located in Australia, the US, and Japan. We put our empirical findings in conversation with scholars of settler colonialism and environmental justice to explain why the state would approve caribou-declining projects with so few economic benefits.

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Shock metamorphism in rock-forming minerals: an overview

Thursday 28 January 2021, 1.00pm

Dr Lidia Pittarello, Museum of Natural History of Vienna, Austria

Impact events (i.e., collisions between planetary bodies) contributed shaping the Earth and, generally, the Solar System. The effects of hypervelocity impacts are recorded in minerals as permanent modifications, induced by the extremely high pressure, temperature, and strain rate. The process inducing these modifications is called shock metamorphism. The identification of shock effects and their correlation with the metamorphic conditions experienced by the investigated material help reconstructing the evolution of the Solar System. In this seminar, shock effects in the most common minerals in terrestrial rocks and meteorites, as well as the methods used for their characterization, will be illustrated

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Historic trends in ocean acidification on coral reefs; relationships to open ocean pH and what they mean for trends in reef biogeochemistry

Thursday 4 February 2021, 1.00pm

Professor Gavin Foster, National Oceanography Centre, University of Southampton

Around a third of all anthropogenic CO₂ emissions have been absorbed by the ocean. This has led to a decrease in ocean pH by approximately 0.1 pH units, and around a 30% decline in dissolved carbonate ion. The latter in particular is thought to have a negative impact on coral calcification by lowering the saturation state of aragonite. However, due to a number of biogeochemical processes (e.g. calcification, organic carbon production) the carbonate system on the reef is not the same as the open ocean, with reef pH determined instead largely by the balance between net ecosystem calcification (NCC) and net ecosystem productivity (NPP). This, coupled with a general lack of environmental monitoring on reefs stretching back beyond the last decade, makes the impact of ocean acidification on tropical corals difficult to assess.

Here we will use a recently developed analytical technique (laser ablation multicollector inductively coupled plasma mass spectrometry) to examine the boron isotopic composition (d11B) and boron content (B/Ca) of coral skeletons recovered from several regions around the globe (Bermuda, Hawaii). These regions were chosen as they are places where decade-long open-ocean carbonate system monitoring (e.g. at BATS and HOTS) as well as local reef monitoring have been performed. We focus here on whether the very high-spatial resolution available with the laser ablation technique (equating to weekly or better temporal resolution) enables seasonally resolved reconstructions of reef pH. By overlapping with intervals of local monitoring we are able to assess the role of coral vital effects relating to biomineralisation vs. variations in reef biogeochemistry in driving the observed pH trends. Unpicking the relative importance of these processes in driving the observed variations in d11B and B/Ca is a challenge, but is essential if the geochemistry of coral skeletons is to be used to reliably reconstruct the carbonate system on reefs beyond the reach of our insufficient instrumental record.

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Why farm? Reconciling the conflicting demands on farmers and farmland

Wednesday 10 February 2021, 1.00pm

Dr Jonathan Storkey (Rothamsted Research) and Professor Richard Pywell (UK Centre for Ecology & Hydrology)

Up until the end of the last century, agricultural policy was dominated by the drive to produce more food, reflected in a tripling of wheat yields since the 1960’s. The unintended consequences associated with this intensification of agricultural production has led to a shift in policy over recent decades towards incentivising environmental management on farmland. The current UK government has committed to environmental enhancement of farmland in its 25 Year Environment Plan, currently being delivered by the Agriculture Bill passing through parliament that aims to reward farmers for delivering public goods. These societal and policy changes put potentially conflicting demands on farms and farmers who, as well as continuing to produce food, now also need to consider how to manage their land to (for example) enhance biodiversity, sequester carbon and reduce greenhouse gas emissions. Reconciling these demands on land will be context specific and depend on soil type, landscape factors, climate and socio-economic factors. New approaches to capturing these interactions using the concept of landscape and farm archetypes will be discussed along with examples of new insights into their contrasting potential to deliver ecosystem services and natural capital.

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The damaging power of absence: The cumulative effects of pore fabric parameters in controlling rock failure

Thursday 18 February 2021, 1.00pm

Dr Cat Greenfield, University of Leicester

The strength of porous rocks in the subsurface is critically important across the geosciences, with implications for fluid flow, mineralisation, seismicity, and the deep biosphere. Most studies of porous rock strength consider the scalar quantity of porosity; the ratio of the void volume to the total volume. Rock strength shows a broadly inverse relationship with total porosity: as porosity increases, rock strength generally decreases. This simplified relationship neglects the effects of pore fabrics, which can vary as a function of the shape, size and distribution of pores within the rock. As with other rock fabrics (e.g., foliations) pore fabrics can be strongly anisotropic in nature, giving the potential for a directional dependence in rock properties.

Dr Luc Doucet, Curtin University, Perth Australia

The Earth’s mantle is currently divided into the African and Pacific domains, separated by the circum-Pacific subduction girdle and each domain features a large low shear-wave velocity provinces (LLSVPs) in the lower mantle. However, it remains controversial as to whether the LLSVPs have been stationary through time or dynamic, changing in response to changes in global subduction geometry. Here we compile radiogenic isotope data on plume-induced basalts from ocean islands and oceanic plateaus above the two LLSVPs which show distinct Pb, Nd and Sr isotopic compositions for the two mantle domains. The African domain shows enrichment by subducted continental material during the assembly and breakup of the supercontinent Pangaea, whereas no such feature is found in the Pacific domain. This deep-mantle geochemical dichotomy reflects the different evolutionary histories of the two domains during the Rodinia and Pangaea supercontinent cycles and thus supports a dynamic relationship between plate tectonics and deep mantle structures.

Dr Richard Clark-Wilson, Centre for Quaternary Research, Royal Holloway University of London

Details to be confirmed.

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