Time filter

Source Type

Santa Cruz de Tenerife, Spain

Witter J.B.,University of Hawaii at Manoa | Hernandez P.,Instituto Tecnologico Y Of Energias Renovables | Hernandez P.,Instituto Volcanologico Of Canarias | Harris A.J.L.,CNRS Magmas and Volcanoes Laboratory | And 2 more authors.
Pure and Applied Geophysics | Year: 2012

We apply a measurement technique that utilizes thermal video of vapor-dominated volcanic plumes to estimate the H 2O gas flux at three degassing volcanoes. Results are compared with H 2O flux measurements obtained using other methods to verify the thermal camera-derived values. Our estimation of the H 2O emission rate is based on the mass and energy conservation equations. H 2O flux is quantified by extracting the temperature and width of the gas plume from the thermal images, calculating the transit velocity of the gas plume from the thermal video, and combining these results with atmospheric parameters measured on-site. These data are then input into the equations for conservation of mass and energy. Selected volcanoes for this study were Villarrica in Chile, Stromboli in Italy, and Santa Ana in El Salvador. H 2O fluxes estimated from the thermal imagery were 38-250 kg s -1 at Villarrica, 4. 5-14 kg s -1 for Stromboli's Central Crater, and 168-219 kg s -1 at Santa Ana. These compare with H 2O flux values estimated by other methods of 73-220, 3-70 and 266 kg s -1, at the three volcanoes, respectively. The good agreement between thermal image-derived results and those estimated by other methods seem to validate this method. © 2012 Springer Basel AG.

Hernandez P.A.,Instituto Volcanologico Of Canarias | Hernandez P.A.,Instituto Tecnologico Y Of Energias Renovables Iter | Melian G.,Instituto Volcanologico Of Canarias | Melian G.,Instituto Tecnologico Y Of Energias Renovables Iter | And 12 more authors.
Surveys in Geophysics | Year: 2015

Active subaerial volcanoes often discharge large amounts of CO2 and H2S to the atmosphere, not only during eruptions but also during periods of quiescence. These gases are discharged through focused (plumes, fumaroles, etc.) and diffuse emissions. Several studies have been carried out to estimate the global contribution of CO2 and H2S emitted to the atmosphere by subaerial volcanism, but additional volcanic degassing studies will help to improve the current estimates of both CO2 and H2S discharges. In October 2008, a wide-scale survey was carried out at Mt. Etna volcano, one the world’s most actively degassing volcanoes on Earth, for the assessment of the total budget of volcanic/hydrothermal discharges of CO2 and H2S, both from plume and diffuse emissions. Surface CO2 and H2S effluxes were measured by means of the accumulation chamber method at 4075 sites, covering an area of about 972.5 km2. Concurrently, plume SO2 emission at Mt. Etna was remotely measured by a car-borne Differential Optical Absorption Spectrometry (DOAS) instrument. Crater emissions of H2O, CO2 and H2S were estimated by multiplying the plume SO2 emission times the H2O/SO2, CO2/SO2 and H2S/SO2 gas plume mass ratios measured in situ using a portable multisensor. The total output of diffuse CO2 emission from Mt. Etna was estimated to be 20,000 ± 400 t day−1 with 4520 t day−1 of deep-seated CO2. Diffuse H2S output was estimated to be 400 ± 20 kg day−1, covering an area of 9.1 km2 around the summit craters of the volcano. Diffuse H2S emission on the volcano flanks was either negligible or null, probably due to scrubbing of this gas before reaching the surface. During this study, the average crater SO2 emission rate was ~2100 t day−1. Based on measured SO2 emission rates, the estimated H2O, CO2 and H2S emission rates from Etna’s crater degassing were 220,000 ± 100,000, 35,000 ± 16,000 and 510 ± 240 t day−1, respectively. These high values are explained in terms of intense volcanic activity at the time of this survey. The diffuse/plume CO2 emission mass ratio at Mt. Etna was ~0.57, that is typical of erupting volcanoes (mass ratio <1). The average CO2/SO2 molar ratio measured in the plume was 11.5, which is typical of magmatic degassing at great depth beneath the volcano, and the CO2/H2S mass ratio in total diffuse gas emissions was much higher (~11,000) than in plume gas emissions (~68). These results will provide important implications for estimates of volcanic total carbon and sulfur budget from subaerial volcanoes. © 2015, Springer Science+Business Media Dordrecht.

Garcia-Yeguas A.,University of Cadiz | Garcia-Yeguas A.,University of Granada | Garcia-Yeguas A.,Instituto Volcanologico Of Canarias | Ibanez J.M.,University of Granada | And 6 more authors.
Geophysical Journal International | Year: 2014

We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the traveltime data of more than 13 000 local earthquakes recorded by the Instituto Geográfico Nacional (IGN, Spain) in the period from 2011 July to 2012 September. The velocity models were performed using the LOTOS code for iterative passive source tomography. The results of inversion were thoroughly verified using different resolution and robustness tests. The results reveal that the majority of the onshore area of El Hierro is associated with a high-velocity anomaly observed down to 10-12-km depth. This anomaly is interpreted as the accumulation of solid igneous rocks erupted during the last 1 Myr and intrusive magmatic bodies. Below this high-velocity pattern, we observe a low-velocity anomaly, interpreted as a batch of magma coming from the mantle located beneath El Hierro. The boundary between the low- and high-velocity anomalies is marked by a prominent seismicity cluster, thought to represent anomalous stresses due to the interaction of the batch of magma with crust material. The areas of recent eruptions, Orchilla and La Restinga, are associated with low-velocity anomalies surrounding the main high-velocity block. These eruptions took place around the island where the crust is much weaker than the onshore area and where the melted material cannot penetrate.These results put constraints on the geological model that could explain the origin of the volcanism in oceanic islands, such as in the Canaries, which is not yet clearly understood. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.

Hernandez P.A.,ITER | Hernandez P.A.,Instituto Volcanologico Of Canarias | Calvari S.,Italian National Institute of Geophysics and Volcanology | Ramos A.,Instituto Volcanologico Of Canarias | And 21 more authors.
Remote Sensing of Environment | Year: 2014

The effusion rate is the most important parameter to gather when a volcanic eruption occurs, because it controls the way in which a lava body grows, extends and expands, influencing its dimensional properties. Calculation of lava flow volume from thermal images collected by helicopter surveys has been largely used during the last decade for monitoring subaerial effusive eruptions. However, due to the depths where volcanic activity occurs, monitoring submarine volcanic eruptions is a very difficult task. The 2011-2012 submarine volcanic eruption at El Hierro, Canary Islands, has provided a unique and excellent opportunity to monitor eruptive processes occurring on the seabed. The use of a hand-held thermal camera during daily helicopter flights allowed us to estimate for the first time the daily and total erupted magma volumes from a submarine eruption. The volume of magma emitted during this eruption has been estimated at 300 Mm3, giving an average effusion rate of ~25 m3 s-1. Thermal imagery by helicopter proved to be a fast, inexpensive, safe and reliable technique of monitoring volcanic eruptions when they occur on the shallow seabed. © 2014.

Hernandez P.A.,Environmental Research Division | Hernandez P.A.,Instituto Volcanologico Of Canarias | Mori T.,University of Tokyo | Padron E.,Environmental Research Division | And 4 more authors.
Earth, Planets and Space | Year: 2011

We report herein the first results of a CO 2 efflux survey carried out at Katanuma volcanic lake, Japan. A total of 110 CO 2 efflux measurements were undertaken at the lake by means of the floating accumulation chamber method during August 2010 to estimate the total CO 2 output from the studied area. Two different mechanisms of degassing were observed during the survey; (1) diffusion through the water-air interface and (2) bubbling. CO 2 efflux values ranged from 0.5 up to 322 g m -2 d -l. In addition, the probability graph was used to distinguish the existence of different geochemical populations in the measured values. Sequential Gaussian Simulation was used to construct a map of CO 2 efflux from 200 simulations and to compute the total CO 2 diffuse emission at the studied area, i.e., 17 ± 0.61 d -1. Copyright © The Society of Geomagnetism and Earth Planetary and Space Sci-ences (SGEPSS).

Discover hidden collaborations