Quantitative volcanic susceptibility analysis of Lanzarote and Chinijo Islands based on kernel density estimation via a linear diffusion process
Risk management stakeholders in high-populated volcanic islands should be provided with the latest high-quality volcanic information. We present here the first volcanic susceptibility map of Lanzarote and Chinijo Islands and their submarine flanks based on updated chronostratigraphical and volcano structural data, as well as on the geomorphological analysis of the bathymetric data of the submarine flanks. The role of the structural elements in the volcanic susceptibility analysis has been reviewed: vents have been considered since they indicate where previous eruptions took place; eruptive fissures provide information about the stress field as they are the superficial expression of the dyke conduit; eroded dykes have been discarded since they are single non-feeder dykes intruded in deep parts of Miocene-Pliocene volcanic edifices; main faults have been taken into account only in those cases where they could modified the superficial movement of magma. The application of kernel density estimation via a linear diffusion process for the volcanic susceptibility assessment has been applied successfully to Lanzarote and could be applied to other fissure volcanic fields worldwide since the results provide information about the probable area where an eruption could take place but also about the main direction of the probable volcanic fissures.
Historic Volcanic Landforms Diversity on Lanzarote
The inventory of the Lanzarote and Chinijo Islands UNESCO Global Geopark (UGG) includes 82 geosites, out of which 17 are linked to the deposits associated with the eruptions of Timanfaya, that took place between 1730 and 1736, and Chinero and Tinguaton eruption, which occurred in 1824. The volcanic field originated during these two historical events occupies a 210 km2 area, which represents 25% of the island surface, and is formed by numerous lava flows and large-scale volcanic lineaments. This volcanic field contains more than 30 cones that show numerous and valuable tectonic, structural, volcanological and geomorphological features that are enhanced by their favorable state of conservation. All of them are included in protected sectors that contribute to its dissemination and conservation. In this chapter, the detailed geological study of the Geosites associated with the historical volcanism of Lanzarote is carried out, a general overview of the main geological landmarks of the evolution of both eruptions. The study of the cones that make up the volcanic field shows that the temporary-space variations of the eruptive styles, the architecture of the resulting volcanoes, as well as their geochemical and tectonic features, represent an excellent example of the complexity of monogenetic volcanism of intraplate oceanic islands.
Monitoring the volcanic unrest of El Hierro (Canary Islands) before the onset of the 2011–2012 submarine eruption
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.