Outwardly predictable volcanoes may harbor an explosive secret
Scientists working with shield volcanoes in the Galapagos Archipelago have found evidence to suggest that volcanoes which ordinarily produce slow-moving rivers of fire have the potential to create far more explosive and dangerous eruptions. Gaining a greater understanding as to how seemingly predictable volcanoes behave is an essential step towards effective hazard assessment and planning.
Volcanic eruptions have played a key role in shaping the development of both our planet, and the lifeforms hardy enough to evolve on its surface. Despite this fact, there are still significant gaps in our species’ understanding of these geological phenomena, and their ability to produce potentially dangerous eruptions.
Some volcanoes have been known to regularly spew lava flows comprised of molten basaltic rock down their flanks, that appear as slow-moving rivers of fire. Other famous volcanoes such as Mt. St Helens in the US and Vesuvius in Italy have the capacity to burst to life with enormous explosive eruptions that pose a serious hazard to any living thing in the vicinity.
One of the reasons that volcanoes are able to create such radically different forms of eruption is rooted in the processes taking place, and the chemical composition of the magma contained in the cavernous spaces that exist beneath them.
New research carried out by an international team of volcanologists suggests that some volcanoes which have been long known to produce the more mundane basaltic eruptions may be capable of changing to more explosive eruptions. The researchers focused their study on the Wolf and Fernandina shield volcanoes located in the Galapagos Archipelago, that to date have only been known to erupt with basaltic flows.
The team carried out a petrological study of microscopic crystals contained within lava deposits and combined their observations with new thermodynamic models in order to glean insights into the flow’s chemical composition, and processes that may be occurring in plumbing system beneath the volcano.
To their surprise, the scientists discovered that, although the volcanoes above spewed out uniform basaltic lava flows, the magma dwelling beneath the geological wonders was extremely diverse, and chemically similar to magma that was found in the wake of explosive eruptions.
According to the team, one possible reason that the volcanoes haven’t unleashed an explosive eruption recently is that the diverse evolved magma hidden away underground is being overwhelmed, or "overprinted," by large quantities of basaltic magma flowing up from further underground.
However, this is not to say that they will not one day alter their behavior. If the volume of basaltic melt emerging from deep within the Earth were to decrease, then the chemically diverse magma could rise to the surface and alter the volcanoes' behavior.
"Although there's no sign that these Galápagos volcanoes will undergo a transition in eruption style any time soon, our results show why other volcanoes might have changed their eruptive behaviour in the past," comments lead author on the paper, Dr. Michael Stock, from Trinity College Dublin. "The study will also help us to better understand the risks posed by volcanoes in other parts of the world – just because they've always erupted a particular way in the past doesn't mean you can rely on them to continue doing the same thing indefinitely into the future."
The paper has been published in the journal Nature.
Source: Trinity College Dublin