A volcanic eruption thousands of miles away could be making sunrises and sunsets more colorful, according to researchers at University of Colorado Boulder.
A team at the school noticed that over the summer, sunrises and sunsets have had more of a purple color to them. They sent up a high-altitude balloon to collect samples of particles in the Earth’s stratosphere, according to a news release from the school last week.
“These particles, or aerosols, scatter sunlight as it passes through the air, which in combination with the absorption of light by the ozone layer, gives sunrises and sunsets that purple tint,” the release says.
On June 22, the Russian volcano called Raikoke erupted, sending ash and volcanic gases from its 700-meter-wide crater up into the atmosphere. The eruption was so big it could be seen by astronauts on the International Space Station, NASA said in a statement.
In a normal, non-volcanic sunset, light from the sun has to travel through a significant amount of Earth’s atmosphere, and blue light scatters off of aerosols it encounters. This means less blue light reaches our eyes from directions near the sun, causing the skies to appear orange and red.
When volcanic aerosols are present in the stratosphere, blue light scattered from aerosols closer to the Earth’s surface can scatter again, this time toward our eyes and cameras. This blue light mixes with the red light already coming from the sun, giving a the sky a purple color.
Lars Kalnajs, a research associate in the Laboratory for Atmospheric and Space Physics at the school, led the project and said this eruption is no cause for concern, but warns that we need to prepare for a bigger one.
“A really big eruption would have a major impact on humanity,” Kalnajs said in the news release.
He cites an eruption on Mount Tambora in 1815 that led to a “year without a summer” due to ash and volcanic material lingering in the atmosphere.
“There were crop failures all over the world, and there was ice in rivers in Pennsylvania that didn’t melt until June,” said Kalnajs.
That is one reason why his team is conducting research after the Raikoke eruption. Preliminary data collected so far shows that some aerosol layers in the stratosphere were 20 times thicker than normal in the wake of the eruption, according to news release.
“It makes you realize that you don’t have to put a whole lot of aerosols into the stratosphere to change its composition,” Kalnajs said. “This was a relatively small volcanic eruption, but it was enough to impact most of the northern hemisphere.”
The group’s research is slated to be published later this year.