8 research outputs found
Causes of unrest at silicic calderas in the East African Rift: new constraints from InSAR and soil-gas chemistry at Aluto volcano, Ethiopia
Get PDFThis work is a contribution to the Natural Environment Research Council (NERC) funded RiftVolc project (NE/L013932/1, Rift volcanism: past, present, and future). W.H., J.B., T.A.M., and D.M.P. are supported by and contribute to the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes, and Tectonics (COMET). Envisat data were provided by ESA. ALOS data were provided through ESA third party mission. W.H. funded by NERC studentship, NE/J5000045/1. Additional funding for fieldwork was provided by University College (University of Oxford), the Geological Remote Sensing Group, the Edinburgh Geological Society, and the Leverhulme Trust. Analytical work at the University of New Mexico was supported by the Volcanic and Geothermal Volatiles Lab at the Center for Stable Isotopes and an NSF grant EAR-1113066 to T.P.F.Restless silicic calderas present major geological hazards, and yet many also host significant untapped geothermal resources. In East Africa this poses a major challenge, although the calderas are largely unmonitored their geothermal resources could provide substantial economic benefits to the region. Understanding what causes unrest at these volcanoes is vital for weighing up the opportunities against the potential risks. Here we bring together new field and remote sensing observations to evaluate causes of ground deformation at Aluto, a restless silicic volcano located in the Main Ethiopian Rift (MER). Interferometric Synthetic Aperture Radar (InSAR) data reveal the temporal and spatial characteristics of a ground deformation episode that took place between 2008 and 2010. Deformation time-series reveal pulses of accelerating uplift that transition to gradual long-term subsidence, and analytical models support inflation source depths of ∼5 km. Gases escaping along the major fault zone of Aluto show high CO2 flux, and a clear magmatic carbon signature (CO2–δ13C of −4.2 to −4.5 ‰). This provides compelling evidence that the magmatic and hydrothermal reservoirs of the complex are physically connected. We suggest that a coupled magmatic-hydrothermal system can explain the uplift-subsidence signals. We hypothesize that magmatic fluid injection and/or intrusion in the cap of the magmatic reservoir drives edifice wide inflation while subsequent deflation is related to magmatic degassing and depressurization of the hydrothermal system. These new constraints on the plumbing of Aluto yield important insights into the behaviour of rift volcanic systems and will be crucial for interpreting future patterns of unrest.Publisher PDFPeer reviewe
Addressing Essential Hydrogeological and Environmental Constraints for Geothermal Development in East Africa
No full textGeothermal energy is vastly under-utilized and represents an exciting means of addressing energy challenges, alleviating poverty, and promoting economic development in the nations of the East African Rift System (EARS). The countries that straddle the rift system are home to a combined population of more than 400 million, a significant proportion of whom do not have access to power or safe drinking water resources. These coexisting water and energy issues have traditionally been tackled as separate challenges. The Combined Power and Freshwater Generation (Combi-Gen) project aims to initiate a disruptive shift in the approach to the twin challenges of energy shortage and water-scarcity through development of a novel thermal chimney driven air-cooled condenser that will capture a substantial portion of the post-flash and reaction turbine geothermal vapour and convert it into potable water, without creating a parasitic power load. In order to enhance the design of such systems, a robust understanding of the geothermal resource and the wider hydrogeological systematics must be obtained. This is essential for assessment of fluid composition, analysis of scaling and corrosive species, flow rate and pressure control, and ultimately optimization of engineering performance. In addition, it is also imperative to gauge the wider hydrological connectivity of geothermal ground waters in order to establish potential impacts on the environment and existing essential water resources
Addressing Essential Hydrogeological and Environmental Constraints for Geothermal Development in East Africa
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Geothermally Sourced Combined Power and Freshwater Generation for Eastern Africa
Get PDFThe Geothermally Sourced Combined Power and Freshwater Generation for Eastern Africa (Combi-Gen) project aims to deliver enhanced power and water resource capabilities to energy-poor and water-scarce nations associated with the East African Rift System (EARS). The Combi-Gen project utilises a robust understanding of geothermal resources and develops a novel thermal chimney driven air-cooled condenser coupled to Trilateral Flash Cycle power generation. This whole systems approach allows for development of a system that produces power and fresh water with no parasitic power load. This paper reports our initial data assessment and modelling results which showcase optimal thermal exchange efficiency parameters and engineering system design
Geothermally Sourced Combined Power and Freshwater Generation for Eastern Africa
No full textThe Geothermally Sourced Combined Power and Freshwater Generation for Eastern Africa (Combi-Gen) project aims to deliver enhanced power and water resource capabilities to energy-poor and water-scarce nations associated with the East African Rift System (EARS). The Combi-Gen project utilises a robust understanding of geothermal resources and develops a novel thermal chimney driven air-cooled condenser coupled to Trilateral Flash Cycle power generation. This whole systems approach allows for development of a system that produces power and fresh water with no parasitic power load. This paper reports our initial data assessment and modelling results which showcase optimal thermal exchange efficiency parameters and engineering system design
