This Purple Sunset In The Rocky Mountains Was Caused By Something On The Other Side Of The World

It’s a concept known as “scattering” whereby particulate matter in the Earth’s ozone layer – such as sulfur dioxide and ash from a volcanic eruption – reflect or refract sunlight, resulting in some colors predominantly showing. John-james Gerber/Shutterstock

When Russia’s formerly dormant Raikoke Volcano erupted in June, it gave off a dramatic display of thick, brown volcanic ash and gases shooting up towards the atmosphere from its 700-meter-wide (2,300-foot) crater that was visible from the International Space Station (ISS). But its effects would last much longer.        

Two months later, Colorado photographer Glenn Randall was hiking and photographing in the mountainous region when he later noticed his images captured a deep violet reflection in the lake waters despite the golden-hued sky above. And he wasn’t alone. A commentary by the University of Colorado at Boulder suggests that viewers around the country have noticed sunrises and sunsets in abnormally purple hues in the last few months. Why? The answer could lie on the other side of the world.

Researchers believe that the June 22 Raikoke eruption may be the culprit. In August, they released a high-altitude weather balloon that measured natural aerosols and other particulate matter 32 kilometers (20 miles) above the ground in Wyoming. They found that aerosol layers were 20 times thicker than normal since the eruption and likely resulted in the unique sunrise. It’s a concept known as “scattering”, whereby particulate matter in the Earth’s ozone layer – such as sulfur dioxide and ash from a volcanic eruption – reflect or refract sunlight, resulting in certain colors predominantly showing.

Raikoke Volcano erupts on June 22, 2019. NASA

It shows that even a relatively small volcanic eruption can have an impact on the other side of the world. And though Raikoke’s eruption is not one to cause concern, atmospheric scientists note that it is the larger eruptions that we should be wary of.  

“A really big eruption would have a major impact on humanity, so it’s something we need to be ready for,” said Lars Kalnajs, a research associate in the Laboratory for Atmospheric and Space Physics (LASP), in a statement.

Take, for example, Mount Tambora’s 1815 eruption that ejected ash and 60 megatons of sulfur dioxide high into the atmosphere, shading the globe and disrupting weather patterns. It is the largest volcanic eruption in recorded history and cooled the average global temperature by as much as 3°C (5.4°F). The year following the eruption is known as the “year without summer,” said Kalnajs. Crop failures around the world resulted in the deaths of 80,000 people who subsequently died from diseases and famine associated with lack of food.  

In more recent history, scientists point to when Mount Pinatubo erupted in The Philippines in 1991. It was the second-largest eruption of this century and produced a giant ash cloud hundreds of miles across containing 20 million tons of sulfur dioxide, dropping global temperatures by about 1°F (0.5°C) in the two years following the eruption.

Altogether, Kalnajs says eruptions like Raikoke are reminders of why monitoring such data is essential.

“It’s really important when major eruptions happen that we get data quickly,” he said. “We need to figure out if this is going to be the kind of thing that impacts hundreds of thousands of people around the world, or is going to be to be more minor?”

If you’re hoping for a purple sunset, Kalnajs says you better have luck on your side: The effects of volcanic ash in the atmosphere doesn’t last long and requires the perfect combination of timing and weather conditions.

The findings will be published later this year.  

Glenn Randall/Facebook
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