Magma Storage and Migration in El Hierro During the Period 2011–2014

The 2011–2014 volcanic episode of El Hierro has become an excellent laboratory for studying the magma plumbing system beneath the island, with tens of works in the literature focusing on the geophysical, geodetic and/or petrological perspective. This chapter mainly focuses on the results obtained through the analysis of the seismicity and ground deformation during the different periods of the activity, including the three months of pre-eruptive unrest, the 5-month-long submarine volcanic eruption, and the magmatic intrusions during the following 2 years after the end of the eruption. All these results, together with those from other petrological and gravimetric studies, have allowed us to obtain a joint description of magma transport and storage at El Hierro Island. Most interpretations point to the presence of a main deep magma storage system below the center of the island feeding both the eruption and the later sill-like magmatic intrusions. The stagnation of the post-eruptive magma accumulations could indicate the presence of stress barriers inhibiting the ascent of magma. This structure may have an important influence on the growth of the island, with similar a contribution from magma storage under the crust as from the eruption itself. Despite all the accumulated knowledge, there are still open questions to be addressed.