Analysis of Volcanic Thermohaline Fluctuations of Tagoro Submarine Volcano (El Hierro Island, Canary Islands, Spain)

Abstract

Temperature and conductivity fluctuations caused by the hydrothermal emissions released during the degasification stage of the Tagoro submarine volcano (Canary Islands, Spain) have been analysed as a robust proxy for characterising and forecasting the activity of the system. A total of 21 conductivity-temperature-depth time series were gathered on a regular high-resolution grid over the main crater of Tagoro volcano. Temperature and conductivity time series, as manifestations of stochastic events, were investigated in terms of variance and analysed by the Generalised Moments Method (GMM). GMM provides the statistical moments, the structure functions of a process whose shape is an indicator of the underlying stochastic mechanisms and the state of activity of the submarine volcano. Our findings confirm an active hydrothermal process in the submarine volcano with a sub-normal behaviour resulting from anti-persistent fluctuations in time. Its hydrothermal emissions are classified as multifractal processes whose structure functions present a crossover between two time scales. In the shorter time scale, findings point to the multiplicative action of two random processes, hydrothermal vents, which carries those fluctuations driving the circulation over the crater, and the overlying aquatic environment. Given that both temperature and conductivity fluctuations are nonstationary, Tagoro submarine volcano can be characterised as an open system exchanging energy to its surroundings.

Identifying Probable Submarine Hydrothermal Spots in North Santorini Caldera Using the Generalized Moments Method

“…The CTD data have been sorted and analyzed using the Generalized Moments Method (GMM), a relatively recently developed mathematical method with various applications in finance time series [28][29][30] and environmental cases [29,31,32]. Our group has successfully used the same modeling method previously to identify the underlying stochastic processes driving the activity of other volcanoes, such as the Kolumbo volcano [33] and Nisyros volcano [34,35], followed by others, e.g., in the case of the shallow underwater volcano El Hierro [36,37]. Previous studies yielded exciting aspects of the underlying dynamics of hydrothermal vent fields during rest and unrest periods.…”

Editorial for Special Issue “Present and Past Submarine Volcanic Activity (1)”

“…Two studies, Olivè Abellò et al [2] and Dura et al [3], applied stochastic calculus tools on temporal series of seawater conductivity and temperature measurements carried out in the water column characterized by the presence of vent of fluids from the seafloor. Fluctuations of the conductivity and temperature properties provide meaningful information about the state of activity of the hydrothermal systems.…”

“…The described statistical technique could be usefully tested in other volcanic contexts in order to determine a large case history of time series of conductivity and temperature fluctuation in different volcanic contexts and phase of activity. In particular, Abello et al [2] showed the results of sampling points located on the main crater of the Tangoro submarine volcano. This latter, placed close to the El Hierro island in the Canarian Archipelago (Spain), was subjected to recent volcanic activity, and its post-eruptive activity is actually strictly monitored.…”