Off the southern coast, meanwhile, pumice stones and a massive sea of ash are drifting across the water. An initial analysis of the material produced by the volcano so far has surprised experts: It provided "clear evidence of the explosive potential" of the volcano, geochemist Domingo Gimeno Torrent of the University of Barcelona told the El Hierro Diaro newspaper.
Most so-called hot spot volcanoes, like those in the Canaries, produce basaltic magma with a relatively small proportion of silicon dioxide (SiO2). SiO2 acts like a glue, producing very viscous magma, leading to a buildup of gases which results in an explosive mixture. The Geochemist Torrent said the El Hierro volcano, however, is feeding off two supplies of lava; a less volatile basalt magma and a much more explosive, SiO2-rich magma.
The risk of large, explosive eruptions in the Canary Islands "should not be neglected," warned geoscientist Rosa Sobradelo from the Spanish National Research Council (CSIC) in Barcelona in a report in the "Natural Hazards and Earth System Sciences" journal. How often such events happen is unknown. But even the most momentous explosions of the past few centuries remained localized.
And there are no fears of large eruptions on land, according to the IGN. The only risk is in the immediate vicinity of the eruption site, where there may be lava flows and rocks flung into the air.