Sometimes, chemistry can be more important for color than even physics.
All across the world, volcanic eruptions remind us of the destructive power residing beneath Earth’s surface.
Molten rock, known as magma, erupts through fissures in Earth’s crust, becoming lava.
If that lava rises above 525 ˚C (977 ˚F), it glows red, with hotter lavas becoming orange or even yellow.
But one volcano, Indonesia’s Kawah Ijen, displays a spectacular blue color.
This unique feature is practically invisible during the day, but is inescapable at night.
Along the flowing lava path, this blue color is ubiquitous.
Bizarrely, the temperatures are insufficient to create a blue hue.
Instead, the blue color is caused by the chemical composition of the environment surrounding the volcano.
The Ijen volcano complex contains the world’s largest lakes of acid, with an average pH of around 0.
The cause of this acidity is widespread sulfur.
Sulfuric acid forms, creating such noxious conditions.
Sulfur also combusts when it contacts oxygen-containing air above a temperature of 360 ˚C (680 ˚F).
It’s this combustion that gives rise to the blue flames, not the intrinsic color of the lava itself.
As the burning sulfur flows down the mountain, miners work to collect this valuable material, even under these dangerous conditions.
Mostly Mute Monday tells the scientific story of a physical phenomenon in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.