When Chile's Calbuco volcano blew its lid on Wednesday afternoon, the eruption sent shockwaves rippling through the Earth's upper atmosphere, like a rock thrown into a pond.
A satellite known as Suomi NPP, a joint NASA and National Oceanic and Atmospheric Administration project, detected the waves rippling out around the volcano when set against the backdrop of the atmosphere's "airglow." The University of Wisconsin's satellite meteorology blog posted unique imagery of the eruption, which shows that it looked like a mushroom cloud from a nuclear test.
Airglow refers to the overall luminosity of the Earth's atmosphere, apart from manmade lights on Earth or lightning in the atmosphere. It occurs because of physical reactions in the planet's upper atmosphere that emit light, which is most visible to astronauts in space and satellites like the Suomi.
Airglow is caused by photochemical reactions in the upper atmosphere, well above the cruising altitude of jet airliners. It occurs because some atoms and molecules get excited from the sun's ultraviolet radiation. This energy is emitted as visible and infrared light, according to Universe Today.
The volcano's ash cloud hit the upper atmosphere like a person belly-flopping into a pool, causing waves to ripple out. Thanks to the Suomi satellite, we can now spot them. The ripples themselves are known as gravity waves, which also occur lower in the atmosphere when towering thunderstorms rapidly displace large amounts of air, causing atmospheric waves to form.