The explosive secret underlying Galapagos Islands’ volcanoes

By Kevin Hidalgo

Quito, Aug 3 (efe-epa).- The remote volcanoes of the Galapagos Islands usually erupt without significant danger or disruption to the surrounding ecosystem or to humans in the vicinity, but below the Earth’s surface they hide a chemically diverse magma that is able to generate powerful explosions, an international investigation has determined.

Located some 1,000 kilometers (620 miles) west of the Ecuadorian coast, those volcanoes – including the Cerro Azul and the Sierra Negra – remain in a constant state of eruption, and although that churning activity poses little local danger, one cannot rule out the possibility that at some point a truly powerful blast will occur because of the largely unknown latent forces deep below.

That is what the magma samples collected from the Wolf and Fernandina volcanoes – on Isabela and Fernandina islands, respectively – by a team of international vulcanologists indicate. The team collected the samples with an eye toward studying the composition of the basaltic lava issuing forth from the fire mountains.

During the course of deciphering the structures of the microscopic crystals in the lava, the team reconstructed the chemical and physical characteristics of the magma.

The magma has an “acidic composition, with a large silica content” similar to the lava from other volcanoes like Cotopaxi, in the Ecuadorian sierra, Benjamin Bernard, a vulcanologist with the National Polytechnic School’s Geophysical Institute, told EFE.

The team – consisting of experts from the United States, United Kingdom and Ecuador – believes that basalt, in fluid form, comprises all of the remaining chemical diversity within the lava, when the amount of magma flowing up from crust below the volcanic cone gets to be sufficient.

In the Galapagos, one of the most diverse regions on the planet and one of the best conserved, there are 23 shield volcanoes – very large mountains – and of those 13 have erupted in the last 10,000 years, Bernard said.

The investigation came about because the group of researchers headed by Britain’s Michael Stock, with Ireland’s Trinity School of Natural Sciences and the main author of the project, wanted to know why these volcanoes were “so boring” and what process caused the “lava compositions to remain constant.”

On the other hand, the team understood that the volcanoes contained a number of chemically different magmas that “are not boring at all” and that “they are only hiding that magma underground,” Stock said.

This can occur when volcanoes are located near a “hotspot,” a temperature anomaly in the Earth’s crust that occurs when hot magma rises up from deep in the Earth to the surface and, specifically, was what created the Galapagos archipelago.

According to the study, the chemical components found in the islands’ volcanoes could become mobile and rise to the surface under certain circumstances, such that the volcanoes that have ongoing seeping eruptions of basaltic lava might begin to show “explosive” activity.

“We know that there were eruptions. For example, the Alcedo volcano did so almost 100,000 years ago, but that doesn’t mean that Wolf and Alcedo are going to have immediate eruptions. Perhaps they might have them within hundreds or thousands of years,” Bernard said.

The Wolf and Fernandina volcanoes, from which the magma samples were taken, experienced basalt eruptions in 2015 and 2020, but now thanks to this investigation scientists know that underneath those volcanoes there are other explosive elements that one day could come to the surface.

Just because they’ve erupted in a particular way in the past doesn’t mean that scientists can have confidence that they will continue doing so indefinitely into the future, the study published by the National Polytechnic Institute said.

The results obtained from the investigation will also help scientists to better understand the risks posed by volcanoes in other parts of the world and how to monitor and evaluate the possible danger.

According to the Geophysical Institute, the Galapagos Islands are considered to be one of the world’s most active volcanic zones.

The archipelago’s 13 islands are of volcanic origin and, on at least eight of them, their volcanoes have showed intense activity during the historically accessible period, especially those fire mountains on Isabela and Fernandina islands.