Hotspot volcanoes

Beyond the lava: where are volcanoes erupting and how long can they last? – National

The incandescent lava spurting from the Cumbre Vieja volcano continues to wreak havoc on the Spanish island of La Palma, destroying buildings and forcing massive evacuations.

The volcanic eruption of La Palma which began on September 19 is one of more than 50 in the world that are marked as “continuous” as of October 12, according to the Smithsonian Institution Global Volcanism Program (GVP).

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This year, 68 eruptions in 29 countries were reported, up from 73 in 2020 and 74 the year before.

Volcanoes have erupted across the world for thousands of years, and many of them remain active continuously for decades.

Despite spectacular images and videos of eruptions that have become more frequent in recent years, volcanologists say there is no reason to suggest that volcanic activity has increased around the world.

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

“The model appears to be quite stable.”

Annual eruptions have remained stable over the past three decades.


Graphic by James Hawkins, Global News


What causes volcanoes to erupt?

Volcanoes erupt when magma formed from molten rock beneath the Earth’s surface rises 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, this causes it to rise. The eruptions are also partly driven by the pressure of the dissolved gas contained in the liquid magma.

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

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

“Magma is produced under certain circumstances where tectonic plates move apart or come together,” Ashwell explained.

Graphic by James Hawkins, Global News


How long can volcanic eruptions last?

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

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

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According to the Smithsonian’s GVP, there have been 101 confirmed eruptions dating back to 1750 that lasted for at least 60 months.

A rash marked as “continuous”, however, does not signify continuous daily activity, but rather uninterrupted intermittent events of at least three months.

This is different from an active volcano, which is erupting or has the potential to erupt in the future. A dormant volcano hasn’t erupted for a long time, but it is expected to erupt again.


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“In general, each volcano has its own characteristic behavior,” said Melanie Kelman, volcanologist at Natural Resources Canada.

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Depending on the type of volcano, there is “huge variability” in how it can behave and how often it erupts, she said.

The range of behaviors includes some that are continually active erupting over and over again for decades, others that are brief and then stop for a long time, as well as low-intensity, long-lasting rashes.

Canada has at least 28 potentially active volcanoes in British Columbia and the Yukon, according to Kelman.

But the country has not seen an eruption for nearly 150 years, the last one occurring in Lava Fork in northwestern British Columbia.

The most recent significant explosive eruption occurred at Mount Meager 2350 years ago. The ash layer from this eruption can still be found as far away as Alberta, according to Volcanoes Canada.

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Canada has at least 28 active volcanoes, according to Natural Resources Canada.


Graphic by James Hawkins, Global News


Mount Garibaldi is another one to watch, UBC’s Gilchrist said, although there is no evidence of seismic activity or gas development.

“However, if it were to erupt, it would be a very big crisis because Squamish is right below and Vancouver could probably be hit by ashfall. It would be a very worrying event.

Due to the region’s tectonic plates, where the oceanic plate is pushed under the North American plate, Gilchrist said he would not be surprised if at some point in the future – probably thousands of years away – he was another explosive or effusive eruption in British Columbia

Can volcanoes be controlled?

What makes responding to rashes difficult is the short warning period, experts say.

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“Sometimes you can get a week in advance for some of the breakouts we’ve been monitoring for the past 50 years or so,” Gilchrist said.

“Other times it can be almost without warning.”

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And once the eruptions start, there is very little you can do to control the lava flow, experts say.

But the damage can be mitigated by a rapid evacuation and the establishment of contingency plans.

Diverting lava flows from built-up areas is another option that has been used in the past, but with little success, said Ashwell of the University of Toronto in Mississauga.


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To better respond to the danger, Gilchrist said it would be helpful to study the history of volcanoes to understand all of the expected eruption styles and the dangers associated with them to nearby communities. But even this shot is not bulletproof due to the unpredictable nature of the eruptions.

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“In an eruption, we can run certain models as the data comes in and try to predict how the dangers are going to play out,” he said.

But when the eruptions are very large, we are “at the mercy of nature,” added Gilchrist.

“The best thing we can do is have escape plans ready to go and hopefully execute them properly and get people out of the way.”

© 2021 Global News, a division of Corus Entertainment Inc.


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