Quantcast
Connect with us

Mount Etna: Volcano is sliding towards the sea and now we know why

Published

on

The southeast flank of Mount Etna in Sicily is sliding towards the sea at a rate of several centimetres a year. This might not sound like much, but the kind of stress that this movement creates inside volcanoes can cause devastating landslides. If, one day, Etna’s movement significantly increases then it could have serious consequences.

With this in mind, scientists such as myself have been studying Etna to try to better understand what’s going on. Now research published in Science Advances presents strong evidence that Etna’s slide isn’t caused by pressure from magma inside the volcano, as previously thought. Instead, it’s likely caused by gravity pulling on Etna’s lower underwater slopes, far from the summit. The researchers emphasise that this means Etna is more susceptible to catastrophic collapse than had previously been realised, and that the same might be true of other coastal and island volcanoes.

ADVERTISEMENT

My colleagues and I first calculated the speed of Etna’s movement earlier this year, showing that the entire edifice slid downslope at an average of 14 millimetres a year between 2001 and 2012. But the whole volcano is also expanding outwards from the summit in all directions, meaning its total annual movement towards the sea is several centimetres.

The new research looks for the first time at what is happening at the underwater foot of the volcano, 1,200 metres below sea level and 12 kilometres from the shoreline. Data from five underwater transponders gathered between April 2016 and July 2017, showed the underwater slope remained stable for a year but then slid four centimetres in one eight-day period before finally stabilising again.

The data shows that the amount of movement is smallest at the summit and biggest at the foot of the volcano. But if movement was caused by the magma inside Etna then the biggest movement would occur near the volcanic centre. The researchers also found that the sea floor movement 12 kilometres from the shore is focused along a single geological fault. But near the coast, the strain is divided between two fault systems.

This all suggests that the movement began offshore and spread towards the summit. There were no associated earthquakes during the eight-day episode, indicating that the movement wasn’t caused by seismic activity. Instead, it’s likely to be the effects of gravity pulling on the volcano.

Etna is expanding outwards from the summit and sliding towards the sea.
GLF Media/Shutterstock

For the past 50 years, the science of volcano movements has been dominated by the idea that most volcanoes have a shallow magma chamber that expands as it fills with magma before an eruption. This causes the walls of the chamber to eventually fracture and allows magma to escape from the side of the volcano. Measuring the volcano’s surface movement would allow you to calculate the depth of the magma chamber. It is this kind of model that is usually used to explain expanding volcanoes.

ADVERTISEMENT

But many scientists including myself have found that while some well-studied volcanoes in Hawaii, Iceland and elsewhere fit this kind of model, other volcanoes contradict it. This suggests there are other factors that explain volcano movement and can affect eruptions.

In the 1990s, volcanologist Andrea Borgia suggested that the steadily increasing amount of lava and volcanic rock deposited near the top of tall volcanoes caused their summits to subside and their slopes to spread outwards. This idea has gained ground as volcanoes around the world provide us with more and more geological evidence, which the new research paper adds to.

Etna’s uncertain future

So what does this mean for Etna? We can say with certainty that catastrophic collapse, in which an entire sector of a volcano slides off in a gigantic landslide, has occurred on the downslope side of other gravitationally sliding volcanoes. The devastation caused by such events, which occur worldwide about four times a century, means that the possibility has to be taken seriously.

ADVERTISEMENT

Unfortunately, we don’t yet have enough detailed knowledge of the build-up to such events to make meaningful predictions about specific volcanoes. So while the authors of the latest paper argue that because Etna’s slide is caused by gravity it makes a collapse more likely, we still can’t give an indication of when or even if this will actually happen.The Conversation

John Murray, Senior Research Fellow, School of Environment, Earth and Ecosystem Sciences, The Open University

ADVERTISEMENT

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Report typos and corrections to: [email protected].
READ COMMENTS - JOIN THE DISCUSSION
Continue Reading

Breaking Banner

Miami-Dade cop relieved of duty after punching irate woman at Florida airport

Published

on

A bad situation turned worse, after a woman missed her flight at Miami International Airport. When police were called, things got even worse.

According to the Miami Herald, body-camera footage, which surfaced Wednesday evening, showed the officer hitting the woman yelling at him.

“You acting like you white when you really Black...what you want to do?” the woman without a mask says.

She then stepped very close to the officer, putting her face against his and that's when he struck her in the face.

Continue Reading

Breaking Banner

Appellate Judge says Mary Trump’s tell-all book can be released

Published

on

Yesterday, a judge paused Mary Trump's tell-all book on President Donald Trump and his family, but Wednesday evening, a New York appellate judge ruled that Simon & Schuster could move forward with releasing the book.

According to the New York Times, Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man will be released in four weeks, on schedule.

"Justice Alan Scheinkman’s ruling, however, put off addressing a central aspect of the bitter spat about the manuscript that has been roiling all month in the Trump family: whether, by writing the book, Ms. Trump violated a confidentiality agreement put in place nearly 20 years ago after a struggle over the will of her grandfather, Fred Trump Sr., Donald Trump’s father," the report said.

Continue Reading
 

Breaking Banner

Trump staff had an inquisition for healthcare workers for Tulsa rally — demanding to know if they leaked staff COVID story

Published

on

President Donald Trump was so incensed that the media learned of his staffers who caught COVID-19 in Tulsa, Oklahoma that he had a kind of inquisition for healthcare workers to investigate if they linked the story.

The Washington Post reported Wednesday that those familiar to his reaction said that outside of the BOK center, Trump campaign staff were being tested before the event. When the information was released, they scrambled, quizzing who leaked the information about the positive cases.

Healthcare workers were "then given a different list of people to test, according to two people with direct knowledge of the events who, like others in this story, spoke on the condition of anonymity to describe internal conversations," said the Post.

Continue Reading
 
 
You need honest news coverage. Help us deliver it. Join Raw Story Investigates for $1. Go ad-free.
close-image