WATCH: Satellite video shows the scale of Calbuco volcano eruption
TORONTO – In 1991, Mount Pinatubo in the Philippines erupted with such force it shot ash 35 km into the sky. But its eruption didn’t just affect the thousands of nearby villagers who were evacuated: its effects were felt around the world.
That has some wondering what the effects will be after the eruption of the Calbuco volcano in Chile early Thursday.
READ MORE: Calbuco Volcano eruption seen from space
When Pinatubo erupted on June 15, 1991, (it was the second time in three days and its most violent), it ejected more than five cubic kilometres of material into the air. The ash cloud rose 35 km into the air.
Fine ash was carried by a nearby typhoon and was carried as far as the Indian Ocean. The cloud of ash circled the globe several times. Though volcanologists had forecast the eruption, saving thousands of lives and property as well as warning aircraft, the effects were widespread.
According to the U.S. Geological Survey, almost 20 million tons of sulfur dioxide was thrust into the stratosphere, causing global temperatures to drop from 1991 to 1993 by about 0.5 C.
In Canada, the eruption caused beautiful sunrises and sunsets. In December 1992, the volcanic ash was responsible for creating one of the darkest lunar eclipses in over a decade (the moon tends to turn a coppery colour during lunar eclipses).
So how does Calbuco compare?
Volcanologists measure the volcanic eruptions on something called the volcanic explosivity index (VEI). The Pinatubo eruption measured about a four to five; Mount St. Helens in 1980 measured a four to five. Though it will take some time for scientists to accurately measure the Calbuco eruption (they need to determine the volume of the eruption was ejected and the height of the plume), preliminary findings suggest that the it measured somewhere around a four.
Heather Wright, a seismologist with the U.S. Geological Survey said that the effects from Calbuco are unlikely to be like that seen after the Mount Pinatubo eruption.
“This is not that big, so the total loading of ash particles in the atmosphere is going to be a lot less from this eruption, pending nothing bigger happens,” she said.
When it comes to volcanic eruptions, what matters in the long run is how far up the ash goes.
Estimates of the height of the Calbuco eruption vary anywhere from 10 km to 20 km. Once that is known for sure, scientists can better estimate the effects.
Thomas Aubry, a PhD student in geophysics at the University of British Columbia, studied the effects of the Mount Pinatubo eruption.
He explained that volcanic aerosols that end up in Earth’s stratosphere tend to remain for about a year, which clearly have a long-term impact. Those that are injected in the troposphere last only about a week or so and therefore have less of an impact on our climate.
“Even if some aerosols are dispersed in the stratosphere, they will likely be confined in the Southern Hemisphere, while Pinatubo aerosols spread all over the globe because it was a tropical eruption,” Aubry said.
“So it’s hard to assess the impact on climate, but I’m confident it won’t be anything comparable to an eruption as big as Pinatubo.”
Locally, the impacts are many: thousands have been evacuated, airports have been closed, and for good reason.
Thin volcanic ash can choke airplanes. When the Eyjafjallajökull volcano erupted in Iceland in 2010, the airline industry was hit hard, losing more than $1 billion when flights were grounded. And this is for good reason: In 1989, volcanic ash from Mount Redoubt, Alaska, knocked out all four engines on a KLM 747 jet. Fortunately, once the plane descended, pilots were able to restart the engines and the plane landed safely.
But there’s more.
The ash can also impact agriculture: ash may prevent sunlight from reaching crops, stunting their growth. They could even be contaminated.
There is also the water to think about. After the Chaitén volcanic eruption in Chile in 2008, many locals faced contaminated water.
As for the local climate, Aubry said that the ash is likely to decrease surface temperatures slightly, but likely only for about a week or so.
“The exact quantity of aerosols depends on the concentration of released gases in aerosols, but it’s very likely gonna be much smaller than Pinatubo even if concentrations are higher,” said Aubry. But he added, “Better data on plume height vs time would be needed to give a more reliable answer.”
Just because the most recent eruption at Calbuco didn’t produce a lot of ash, that’s not to say there won’t be future eruptions. As of April 24, there have been three pulses of activity.
“It’s unknown how long this eruption will last,” said Wright.