INVOLCAN, the Volcanological Institute of the Canaries, along with PEVOLCA (the Civil Protection Plan for Volcanic Risk), has raised the alert status in parts of El Hierro to "Yellow" after increasing signs that we could be headed towards new eruptive activity in the Atlantic Island. The increased seismicity reported over the weekend was part of the rationale, however, new data suggests that the 2-3 centimeters of deformation have occurred over the last few days, all supporting the notion that magma is intruding under El Hierro. Remember, when magma intrudes the crust, it has to make room for itself, so deformation is one of the tell-tale signs of this intrusion (however, deformation can occur due to other processes as well, but combined with seismicity, magma is usually a good culprit). This new deformation is centered to the northwest of the submarine vent that opened last fall, putting it near the El Julan and La Dehesa areas on the coast. As for the seismicity, the island registered over 200 earthquakes on Tuesday alone.
A graph showing the seismicity (red bars) and carbon dioxide emissions (blue line) recorded at the HIE01 station on El Hierro in the Canary Islands. The increase in carbon dioxide during late April and early May is potentially the precursory sign of the new intrusion of magma that may be going on under El Hierro now. Image courtesy of INVOLCAN. INVOLCAN posted a figure showing the seismicity and carbon dioxide emissions from the HIE01 station (see above) at eruptive activity over the past year at El Hierro and they suggest that a brief increase in carbon dioxide emissions during April and early May of this year could be the precursory events for this new intrusion of magma, with the new seismicity showing magma is now on the move to the surface. However, the direct connection between the CO2 spike (which coincided with a lull in seismicity) is still very unclear. Remember, as magma intrudes and rises, it also loses dissolved gases like carbon dioxide, so an increase in CO2 could be new (undegassed) magma being introduced into the magmatic system. {Special thanks to many Eruptions readers for keeping us up to date in the comments and on Twitter.}
