Magma effect on the electrical resistivity: La Palma (Canary Islands)

The recent eruption in La Palma (September 19^th-December 14^th, 2021) represents a unique opportunity to assess the effect of the magma on the electrical resistivity distribution of the subsoil. On the one hand, the presence of magma generates strong resistivity contrasts with the hosting units, since magmas contain dissolved water in their composition that reduces its resistivity. On the other hand, a 3-D resistivity model of La Palma Island was performed in 2019, proving us with a baseline model.

Several electromagnetic experiments have been performed in the island since the beginning of the volcanic eruption, in order to understand the changes of the resistivity associated to the magma intrusion, as well as the potential of these methods for the volcanic monitoring.

Here, we present in the frame of PIXIL project some preliminary results of a set of tests conducted against the 3-D resistivity model of the island (baseline model), to determine the characteristics of the detectable magmatic body at depth with the magnetotelluric data available. Understanding the extension, geometry, pathway, etc. of the magma is essential since many volcanic hazards are related to the size and depth of the sources of magma, especially in La Palma Island which is one of the highest potential risks in the Canary Islands.