Study of the physical-chemical anomalies over the main crater of Tagoro submarine volcano, El Hierro Island

Abstract

Five years after the eruption of Tagoro submarine volcano, the representative residual hydrothermalism following an eruption event, persists in the main crater, playing an important role in the supply of heat and CO2 to the ocean. The discharges of CO2 together with reduced species as Fe(II), disturb the seawater physical-chemical properties in the surrounding areas of the volcano, creating a highly corrosive environment. The seawater interactions result in a wide range of ORP and pH, related with increases of temperature, often accompanied by decreases in salinity, oxygen reduction and turbidity rise parameters, being able to establish strong relationships and proportional responses. Although a great diversity of hydrothermal activity associated to volcanic structures exist around the deep ocean, there is not too much knowledge about the quantification, evolution and temporal continuity of these physical-chemical anomalies from diffuse lowtemperature hydrothermal vents. The present results highlight that the degasification stage over the main crater of Tagoro submarine volcano still remain active. The three time series carried out, have registered interrupted physical-chemical anomalies, maybe associated with different degassing process rates from the low-temperature diffuse vent. Maximum anomalies detected are 1.1971±0.3821 ºC for potential temperature, -0.1399 ± 0.0330 for salinity, -0.4673±0.0799 units for pH, 7.7155±0.1210 NTUs for turbidity and -9.0769±0.8251 μmol kg-1 for the dissolve oxygen. Variability patterns confirm the existence of a high lineal positive correlation between potential temperature and salinity which match inversely with a high significant descending of pH and oxygen, for all time series registered. Simultaneously, current velocities direction and pattern, confirmed the absence of its influence to the anomalies observed over the main crater.