Carbon dioxide is the most abundant, non-condensable gas in volcanic systems, released into the atmosphere through either diffuse or advective fluid flow. The emission of substantial amounts of CO2 at Earth’s surface is not only controlled by volcanic plumes during periods of eruptive activity or fumaroles, but also by soil degassing along permeable structures in the subsurface. Monitoring of these processes is of utmost importance for volcanic hazard analyses, and is also relevant for managing geothermal resources. Fluid-bearing faults are key elements of economic value for geothermal power generation. Here, we describe for the first time how sensitively and quickly natural gas emissions react to changes within a deep hydrothermal system due to geothermal fluid reinjection.
For this purpose, we deployed an automated, multi-chamber CO2 flux monitoring system within the damage zone of a deep-rooted major normal fault in the Los Humeros Volcanic Complex (LHVC) in Mexico and recorded data over a period of five months. After removing the atmospheric effects on variations in CO2 flux, we calculated correlation coefficients between residual CO2 emissions and reinjection rates, identifying an inverse correlation of ρ = -0.51 to -0.66. Our results indicate that gas emissions respond to changes in reinjection rates within 24 hours, proving an active hydraulic communication between the hydrothermal system and Earth’s surface. This finding is a promising indication not only for geothermal reservoir monitoring but also for advanced long-term volcanic risk analysis. Response times allow for estimation of fluid migration velocities, which is a key constraint for conceptual and numerical modelling of fluid flow in fracture-dominated systems.
Objectives: (1) To establish a framework for monitoring global climate change by detecting changes in permafrost ground temperatures in the mountains of Europe. (2) To develop methods of mapping and modelling the distribution of thermally sensitive mountain permafrost, and predicting climatically-induced changes in this distribution. (3) To provide new, process-based methods for assessing environmental and geotechnical hazards associated with mountain permafrost degradation. Background and Work Content: European mountains are characterised by the presence of permafrost (permanently frozen ground) at higher altitudes which is only a few degrees below zero, and therefore forms terrain that is highly sensitive to climate warming. Climate modelling suggests that the amplitude of global warming due to greenhouse forcing will increase with increasing latitude and altitude, so that the mountains of Europe offer an ideal location for monitoring future climate change and its environmental impacts. Atmospheric warming will lead to a rise in permafrost temperatures and near-surface thawing, with potentially grave consequences to engineering structures and mountain slope stability. The PACE programme will initiate a European permafrost Monitoring Network on a latitudinal transect across the mountains of Europe. The objectives of this project will be achieved through six integrated work packages. WP1 Permafrost temperature monitoring. This will involve drilling new boreholes to depths of 8-80 m, and automatic logging of ground temperatures. The European Permafrost Monitoring Network will provide early warning of climate change. WP2 Mapping of permafrost distribution, depth and characteristics based on geophysical techniques will provide refined geophysical field techniques for permafrost assessment and mapping that will be incorporated in WP6, together with new data on permafrost distribution and character. WP4 Energy balance measurements and permafrost distribution modelling. Field measurements taken at microclimatological monitoring stations, together with digital elevation models will allow improved modelling of permafrost distribution patterns. WP5 Thermally controlled geotechnical centrifuge modelling of permafrost degradation processes. Physical modelling of permafrost degradation processes will include thaw subsidence impact on foundations and slope instability processes resulting from permafrost thaw. WP6 Process-Based Mountain Permafrost Instability Hazard Predition in the Context of Global Warming: Technical Guidelines. Integration of the previous five work packages will be undertaken in the context of geotechnical and environmental hazard prediction, to provide new practical guidelines designed to facilitate risk assessment and project planning in the mountains of Europe. Prime Contractor: University of Wales, Cardiff, Department of Earth Science; Cardiff/UK.