Beyond the lava: Where are volcanoes erupting and how long can they last?

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Red-hot lava emanating from the Cumbre Vieja volcano is wreaking havoc on the Spanish island of La Palma, destroying buildings and forcing massive evacuations.

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The La Palma volcanic eruption that began on September 19 is one of more than 50 worldwide marked as “ongoing” as of October 12. Smithsonian Institution’s Granthshala Volcanism Program (GVP).

There have been 68 eruptions in 29 countries this year, compared to 73 in 2020 and 74 a year ago.

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Volcanoes have been erupting around the world for thousands of years, many of which have been continuously active for decades.

Despite spectacular images and videos of eruptions becoming more common in recent years, volcanologists say there is no reason to suggest that there has been an increase in volcanic activity around the world.

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“There is no evidence that the number or scale or size of volcanic eruptions on Earth is changing at all,” said Paul Ashwell, assistant professor of earth sciences at the University of Toronto Mississauga.

“The pattern seems fairly stable.”

Volcanoes erupt when magma made of molten rocks beneath the Earth’s surface rises up through cracks in the Earth’s crust.

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Since semi-molten or molten magma is lighter or more buoyant than its surroundings, it rises up. Eruptions are also partly driven by the pressure of the dissolved gas contained in the liquid magma.

Volcanic eruptions typically occur in three types of regions: mid-ocean ridges, subduction zones, and hot spots.

The movement of tectonic plates – the sections that make up the Earth’s crust – is made possible by heat from the Earth’s interior that drives volcanic activity in these regions.

“Magma is generated under certain circumstances where tectonic plates are moving apart or towards each other,” Ashwell explained.

The La Palma volcanic eruption has now entered its fourth week.

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Explosions can last from less than a minute to hundreds of thousands of years, said researcher Johan Gilchrist from the Department of Earth, Ocean and Atmospheric Sciences at the University of British Columbia.

According to the Smithsonian’s GVP, there were 101 confirmed eruptions in 1750 that lasted at least 60 months.

However, an eruption marked “continuous” does not mean continuous daily activity, but rather intermittent events without a break of at least three months.

This is different from an active volcano, which is either erupting or likely to erupt in the future. A dormant volcano has not erupted for a long time, but is expected to erupt again.

“Generally speaking, each volcano has its own signature behavior,” said volcanologist Melanie Kellman of Natural Resources Canada.

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There is “huge variability” on how it might behave, depending on the type of volcano, and the frequency of its eruptions, she said.

The range of behaviors includes some that have been continuously active for decades, others that are brief and then cease for longer periods, as well as those that last longer, low-level eruptions.

According to Kellman, there are at least 28 potentially active volcanoes in British Columbia and Yukon in Canada.

But the country hasn’t seen an eruption in nearly 150 years, the last time being at a lava fork in the northwest BC.

The most recent significant explosive eruption occurred at Mount Major 2,350 years ago. The ash layer from that explosion can still be found as far away as Alberta, according to Volcano Canada.

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Mount Garibaldi is another one to keep an eye on, UBC’s Gilchrist said, although there is no evidence of seismic activity or gas release.

“However, if it were to erupt, it would be a very significant crisis because Squamish is right below it and Vancouver could probably be affected by the ash fall. That would be a very worrying event.

Because of the region’s tectonic plates, where the oceanic plate is being pushed under the North American plate, Gilchrist said he wouldn’t be surprised if at some point in the future — perhaps thousands of years from now — another eruption or BC . flow explosion in

Experts say it is challenging to respond to the eruptions, given the short duration of the warnings.

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“Sometimes you can get a week ahead for some of the eruptions that we’ve monitored over the past 50 years,” Gilchrist said.

“Other times, it can happen almost without warning.”

And once the eruption begins, little can be done to control the lava flow, experts say.

But losses can be minimized by making timely withdrawals and contingency planning.

U of T Mississauga’s Ashwell said diverting lava flows away from built-up areas is another option that has been used in the past, but with little success.

To better respond to the threat, Gilchrist said it would be helpful to study the history of volcanoes, to understand all expected styles of eruption and associated hazards to surrounding communities. But even that plan is not bulletproof due to the unpredictable nature of the explosions.

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