Melting ice gave Etna its cone, researcher says


Offshore data contradicts established theory about Sicily’s famous volcano. Andrew Masterson reports.


Cone of science: Mt Etna owes its shape to the sea, research suggests.
Cone of science: Mt Etna owes its shape to the sea, research suggests.
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Sicily’s Mount Etna, one of the most famous volcanoes in the world, may have got its shape because of ultra-high sea levels 100,000 years ago, new research suggests.

In a paper in the journal Episodes, prominent UK volcanologist Iain Stewart from the University of Plymouth argues the current theory about Etna – that its shape was formed by tectonic shifts – is wrong. In its place, he proposes that the volcano’s instantly recognisable cone was triggered by high water levels in the Mediterranean, caused by melting ice sheets.

“Mount Etna is arguably one of the most iconic volcanoes on the planet, but 100,000 years ago there would have been no cone-like structure such as you see today,” he says.

“I had always been interested to know what prompted that to happen but I believe the dates of sea levels rising – and how they correspond to the volcano physically changing – offer a potential explanation.”

Etna’s history begins around 500,000 years ago and takes place for millennia underwater. Around 220,000 years ago, matters moved above above-ground, with the formation of a fissure. This led to the formation of a chain of eruptive centres along the present Sicilian coast.

At some point later than 130,000 years ago, however, something happened, and Etna transformed from a fissure-type volcano into a cluster of “stratovolcanoes” – conical structures comprising successive layers of lava and ash – significantly inland.

In his paper, Stewart suggests that new offshore structural studies throw the prevailing tectonic explanation for the change into question. Instead, he suggests that a period of glacial melting that began around 124,000 years ago, known as the Eemian period, may have been responsible.

Research suggests that meltwater from the West Antarctic and Greenland ice sheets during the period pushed up sea levels by as much as 5.5 metres.

Stewart suggests that the sea rise functioned to sea off Etna’s coastal outlets, forcing a reorganisation of subterranean tunnels, thus affecting magma flows, with the inland cone developing as a result.

“The precise sensitivities of the plumbing beneath Etna has always been something of a mystery, but exploring how sea levels interact with its fault lines could shed new light on its creation and future,” he says.

If further evidence supports the theory, he adds, the same forces could have been behind the shaping of other volcanoes, including Italy’s Mount Stromboli and Soufrière Hills on the island of Monserrat in the Caribbean.

  1. http://www.episodes.org/articleDetail.do?p=1963
  2. http://www.episodes.org/articleDetail.do?p=1963
  3. https://www.nature.com/articles/35007053]
  4. https://cosmosmagazine.com/geoscience/seven-of-the-biggest-volcanic-explosions-the-world-has-ever-seen
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