Groundwater flow and volcanic unrest

Abstract

Hydrology around active volcanoes is strongly controlled by the interaction between groundwater, and the fluids, dissolved elements and heat associated with magmatic intrusion. The chemical and mechanical processes associated with magmatic unrest can result in observable changes in the hydrothermal system. Consequently, observations of chemical and physical hydrothermal variations may provide insights into the state of volcanic activity. Additionally, the interaction between hydrological and volcanic systems leads to the presence of high-temperature, pressurised, and often acidic fluids, which add to, and intensify, the volcanic hazard. In the following chapter we present the major components of, and controls on, magmatic hydrothermal systems focusing on the mutual perturbation between the groundwater flow system and the volcanic system. We explore how these conditions can be modified by volcanic unrest and we identify feedbacks between dynamic hydrothermal behaviour and on-going unrest. The interaction between these systems, and therefore the associated monitoring signals, are the result of complex groundwater-volcano coupling within multi-phase flow system in evolving lithologies. Nonetheless, detailed monitoring of hydrothermal and hydrological behaviour can provide insights into unrest and the evolution of hazards at restless volcanoes.

Tracking the recent dynamics of Mt. Vesuvius from joint investigations of ground deformation, seismicity and geofluid circulation

“…9) according to which the observed phenomena are the effect of significant pressure variations in the hydrothermal reservoir. Such variations promote crustal strain changes (deformation and seismicity), which in turn affect fluid circulation 40,41 . Crustal strain and/or sealing due to hydrothermal alteration 39 likely forced the closure of some pathways towards the crater area.…”

Hydrochemical Characterisation of High-Fluoride Groundwater and Development of a Conceptual Groundwater Flow Model Using a Combined Hydrogeological and Hydrochemical Approach on an Active Volcano: Mount Meru, Northern Tanzania

“…The model was developed based on hydrogeochemical processes, ground-water mineralisation, spring settings, and groundwater level in the shallow wells. The model suggests the influence of the volcanic gases in the groundwater chemistry of the two hydrothermal springs (S42 and S43) and the two springs from the discharge area (S18 and STP6), which are flowing from the deepest flow line [33][34][35]. The model shows the increase of groundwater mineralisation with water residence times.…”

“…The strong positive correlation of TDS with Na + , K + , HCO 3 − + CO 3 2− , SO 4 2− , and Cl − indicates that the concentration of these elements progressively increases together with the mineralisation of the groundwater along the groundwater flow path in response to the main hydrogeochemical processes [29]. The strong positive correlation of Cl − with Na + , K + , HCO 3 − + CO 3 2− , and SO 4 2− suggests the evapoconcentration along the flow path, the localised dissolution of evaporitic salts such as halite (NaCl), sylvite (KCl), gypsum (CaSO 4 .2H 2 O), anhydrite (CaSO 4 ), thenardite (Na 2 SO 4 ), and mirabilite (Na 2 SO 4 .10H 2 O) [29,36], and the admixture of volcanic gases (which are containing lots of CO 2 , SO 2 , HCl, HF) as Mount Meru is an active volcano [33][34][35]. The significant moderate positive correlations of F − with Na + and K + indicate that the progressive increase of F − goes parallel with the increase in alkaline elements (suggesting progressive rock-water interaction), whereas the significant weak negative correlations of F − with Ca 2+ and Mg 2+ indicate that the progressive increase of F − goes parallel with the decrease in alkaline earth elements along the groundwater flow paths, through precipitation of carbonate minerals: aragonite, calcite, and dolomite.…”

Delineating a Volcanic Aquifer Using Groundwater-induced Gravity Changes in the Tatun Volcano Group, Taiwan

“…In the following development, we will describe in detail how our gravity measurements were collected and processed, and how two groundwater ow models are constructed to model gravity changes for inferring the aquifer boundaries. Because groundwater ow is important for understanding volcanic unrests (Jasim et al, 2018), this result from this study will bene t the understanding of the aquifer distribution in the TVG for volcanic hazard modeling in northern Taiwan.…”