Monitoring the volcanic unrest of El Hierro (Canary Islands) before the onset of the 2011–2012 submarine eruption

Abstract

On 10 October 2011, a submarine volcanic eruption started 2 km south from El Hierro Island (Spain). Since July 2011 a dense multiparametric monitoring network was deployed all over the island by Instituto Geográfico Nacional (IGN). By the time the eruption started, almost 10000 earthquakes had been located and the deformation analyses showed a maximum deformation of more than 5 cm. Earthquake migration from the north to the south of the island and acceleration of seismicity are in good correlation with changes in the deformation pattern as well as with some anomalies in geochemical and geomagnetic parameters. An earthquake of local magnitude 4.3 at 12 km depth (8 October 2011) and shallower seismicity a day after, preceded the onset of the eruption. This is the first time that a volcanic eruption is fully monitored in the Canary Islands. Data recorded during this unrest episode at El Hierro will contribute to understand reawakening of volcanic activity in this region and others of similar characteristics.

Volcanic signatures in time gravity variations during the volcanic unrest on El Hierro (Canary Islands)

“…However, no significant changes were observed in either the transversal level or the other instrumental data recorded at the same time. The vertical displacement of the GPS antenna installed at the same observation site increased by about 0.3 cm during same days (Figure 4e), which coincided with the general trend observed at other GPS stations on the island [see López et al, 2012] following the inflation episode preceding the eruption. There was no evidence of any type of anthropogenic noise at the time, although we cannot discard this possibility.…”

“…that a path for the magma to the surface was opened and provoked the submarine eruption [López et al, 2012;Perez-Torrado et al, 2012;Martí et al, 2013]. Other gravity change of similar amplitude, and coinciding with the occurrence of various seismic events of magnitude M bLg > 3.6 recorded 20 h before (Figure 5a), could be likewise related with the rupture process and magma ascent to the surface.…”

“…Along with certain other observational techniques, the analysis of continuous gravity measurements allows the temporal evolution of volcanic processes to be studied and can make an important contribution to the investigation of subsurface mass redistributions and density changes, magmatic processes, and changes in elevation and seismicity. and three magnetometers [López et al, 2012]. A tiltmeter network was also installed to monitor ground deformations [Arnoso et al, 2012], while a control gravity network, in place since 2003, was used to study gravity variations in terms of subsurface mass/density changes due to volcanic activity.…”

Synthesis of global satellite observations of magmatic and volcanic deformation: implications for volcano monitoring & the lateral extent of magmatic domains

“…The lack of a significant increase in the Parker et al, 2015), decision makers with responsibility for volcanic hazard (indicative durations) and duration of unrest and eruption ( 2 unrest periods as described by Phillipson et al, 2013). Examples of eruptions with different durations of pre-eruptive unrest are indicated by volcano name and eruption date (López et al, 2012;Delgado et al, 2014), while volcano name and arrows show episodes of unrest. b.…”

An Overview of Geodetic Volcano Research in the Canary Islands

“…A total of 19 historical subaerial eruptions have been recorded in the Canary Islands (Siebert et al, 2011). The most voluminous eruption took place, 1730-1736, in Lanzarote (second oldest), the last on-shore eruption was at Teneguía Volcano (La Palma) in 1971 and the most recent was submarine on the island of El Hierro in -2012(Carracedo et al, 2012López et al, 2012, González et al, 2013.…”