Lava samples have revealed a new truth about the geological make-up of the Earth’s crust and could have implications for volcanic eruption early warning systems, according to a new study.
It was previously understood that cooled lava from so-called “hot spot” volcanoes was “pristine” magma from the melting mantle, tens of kilometers under the Earth’s surface, says volcanologist Teresa Ubide of the University of Queensland.
“This isn’t quite the case—we’ve been misled, geologically deceived,” Ubide says.
“For decades, we have considered hot spot volcanoes to be messengers from the Earth’s mantle, offering us a glimpse into what’s happening deep under our feet. But these volcanoes are extremely complex inside and filter a very different melt to the surface than what we’ve been expecting,” Ubide says.
“This is due to the volcano’s intricate plumbing system that forces many minerals in the magma to crystallize.”
Ubide says the minerals are being recycled by the rising magma, changing their overall chemistry to “appear” pristine, which is an important new piece of the jigsaw to better understand how ocean island volcanoes work.
“We have discovered that hot spot volcanoes filter their melts to become highly eruptible at the base of the Earth’s crust, situated several kilometers below the volcano,” she says.
“The close monitoring of volcanoes can indicate when magma reaches the base of the crust, where this filtering processes reaches the ‘tipping point’ that leads to eruption. Our results support the notion that detection of magma at the crust-mantle boundary could indicate an upcoming eruption,” Ubide says.
“This new information takes us one step closer to improving the monitoring of volcanic unrest, which aims to protect lives, infrastructure, and crops.”
Hot spot volcanoes make up some of the world’s most beautiful landscapes, such as the Canary Islands in the Atlantic and Hawaii in the Pacific.
The researchers analyzed new rock samples from the island of El Hierro, in Spain’s Canary Islands, just southwest of Morocco. This data was combined with hundreds of published geochemical data from El Hierro, including the underwater eruptions in 2011 and 2012.
The team then tested the findings on data from ocean island hot spot volcanoes around the world, including Hawaii.
Ubide says hot spot volcanoes are also found in Australia. “Southeast Queenslanders would be very familiar with the Glass House Mountains or the large Tweed shield volcano, which includes Wollumbin (Mount Warning) in New South Wales,” she says.
“Hot spot volcanoes can pop up ‘anywhere’, as opposed to most other volcanoes that occur due to tectonic plates crashing into each other, like the Ring of Fire volcanoes in Japan or New Zealand, or tectonic plates moving away from each other, creating for example the Atlantic Ocean,” Ubide says.
“Southeast Queensland hot spot volcanoes were active millions of years ago. They produced enormous volumes of magma and make excellent laboratories to explore the roots of volcanism.
“There are even dormant volcanoes in South Australia, that could erupt with little warning, that would benefit from better geological markers for early detection.”
The research appears in Geology.
Source: University of Queensland