An enormous dome has been discovered growing in the Central Andes above the world’s largest active magma store.
Found in the Altiplano-Puna Plateau - the second highest plateau on the planet - the dome stretches more than a kilometre high (3,280 feet), making it 172 metres taller than the world’s tallest building in Dubai. Researchers say this massive structure is the result of an injection of magma from below.
"The dome is the Earth's response to having this huge low-density magma chamber pumped into the crust," says one of the team, Noah Finnegan from the University of California, Santa Cruz.
How did we all miss a massive dome of Earth rising a kilometre above the surface?
It just so happens to be hidden within the Altiplano-Puna Plateau - a high, dry region, littered with volcanoes, that extends for some 2,000 km along the Central Andes, with an average height of 4,000 metres.
The Central Andes constitutes an even larger plateau, encompassing southern Ecuador, northwestern Bolivia, and most of Peru. Together, the Central Andes, Southern Andes, and Patagonia make up the Andes, the longest continental mountain range in the world.
So it’s easy to see how something could elude us in the middle of all that.
Back in 2014, the researchers used seismic imaging - a tool that bounces sound waves off underground rock structures - to reveal the enormous size and extent of the Altiplano-Puna magma body.
They found that this massive zone of melted rock is a whopping 11 kilometres thick and 200 kilometres in diameter - much larger than previous estimates.
They’ve since gone back to take a closer look at the internal structure of the Altiplano-Puna plateau, and have identified a kilometre-high topographical dome, with the dormant Uturuncu Volcano sitting right in the centre of it.
"People had known about the magma body, but it had not been quantified that well," says one of the researchers, Jonathan Perkins. "In the new study, we were able to show a tight spatial coupling between that magma body and this big, kilometre-high dome."
The dome is located within the Altiplano-Puna Volcanic Complex, which sits in the southern part of the Altiplano-Puna Plateau. Roughly 10 million years ago, this was one of the most volcanically active places on the planet, and was shaped by a series of super-volcano eruptions over several thousand years.
Since the 1990s, satellite surveys have been conducted in the area, and have shown consistent uplifting of the surface - in some places at a surprisingly rapid rate.
The Uturuncu volcano at the heart of the newly discovered dome has been rising by about 1 centimetre every year, and the team took it upon themselves to figure out why.
"We think the ongoing uplift is from the magma body," says Perkins. "The jury is still out on exactly what's causing it, but we don't think it's related to a super-volcano."
The researchers suspect that activity in two tectonic plates in the region - the South American continental plate and the Nazca oceanic plate - has allowed magma to seep into the crust and feed the volcanoes.
Meanwhile, water is also being released by this activity, which changes the melting temperature of the mantle rock in the lower Nazca oceanic plate, prompting it to melt and rise into the overlapping South American continental plate.
So the same process that once created our continents has been fuelling the growth of this enormous dome.
"This is giving us a glimpse into the factory where continents get made," says Perkins.
"These big magmatic systems form during periods called magmatic flare-ups when lots of melt gets injected into Earth's crust. It's analogous to the process that created the Sierra Nevada 90 million years ago, but we're seeing it now in real time."
The research has been published in Nature Communications.