'Boring' volcanoes hide explosive chemicals underground and may cause dangerous eruptions in future: Study
Do not let the "boring" volcanoes such as the ones in the Galápagos Islands fool you. Although their eruptions are not explosive, they could have a stash of ingredients necessary for an explosion hidden in their underground systems, according to a new study.
Researchers discovered the underground reservoirs of explosive chemicals in two volcanoes in South America's Galápagos Islands. In the future, they suspect that these might turn explosive like Washington's Mount St Helens, which is known to explode and spew ash miles away. Making them dangerous are ingredients such as silica, a constituent of sand, and dissolved water. "The more you have those molecules, the more explosive it gets," Dr Benjamin Bernard, a volcanologist at Instituto Geofísico and co-author of the study, told MEA WorldWide (MEAWW).
However, volcanoes such as those in the Galápagos Islands do not pose that kind of risk. Dr Michael Stock from Trinity College Dublin and his colleagues have called them boring "because they have produced very similar eruptions for millions of years." Their lava is made of molten basalt rocks -- a dark-colored volcanic rock that is rich in minerals such as iron and magnesium and low in silica. During an eruption, the lava flows out at a walking pace, allowing people to escape. But they do cause some damage to property. Those in Iceland are Hawai also belong to the same category of basaltic volcanoes.
Dr Stock and the team wanted to figure out why Galápagos Island's volcanoes do not explode. "How can magmas ascending all the way through the Earth’s crust (~10-15 km) always end up identical when they erupt at the surface?" he wondered.
So they studied tiny crystals present in the lava to identify the chemicals. The analysis revealed that underneath these volcanoes, the magma had a different composition. In other words, it had ingredients to set off an explosion.
But what keeps those chemicals from shooting up in Galápagos Island's? According to Dr Stock, the large volume of basalt flushing through the crust overshadows the explosive ones. "You can think of it like having a drop of coke in the bottom of a glass and then filling it with water – even though the coke is there, you still essentially have a glass of water. The same here – you have a drop of rhyolite [explsoive] magma mixing with an enormous volume of basalt moving through the crust," he said.
Researchers do not expect the transition to happen anytime soon. In the future, tectonic plates might carry the volcanoes away, resulting in a lower volume of basalt. It would be good to study if lower basalt flushing results in a change in eruption style, Dr Stokes explained.
But the researchers have only studied volcanoes in Galápagos Island. They are not sure whether similar basaltic ones in Iceland, Hawaii hold diverse chemicals, including explosive ones, beneath them. It would be good to look for them too, Dr Stokes said.
"The finding helps us to understand much better the functioning of Galápagos and, as an extension, basaltic volcanoes. In itself, it won't immediately change the hazard assessment for Galápagos volcanoes as we still have many questions to answer to build an eruptive scenario based on those results," Dr Bernard said.