Rainbows can mean big trouble on fault lines

The Danakil Depression in Ethiopia looks like a different planet, painted in neon yellows, vibrant greens, and rust reds. These colors are not decorative; they are the chemical signature of a landscape that is actively trying to dissolve itself. Sitting 410 feet below sea level, Danakil is one of the hottest places on Earth, where the triple junction of shifting tectonic plates allows magma to sit agonizingly close to the surface.

Groundwater here is heated by volcanic activity and rises through deep salt deposits, emerging as boiling brine. As the water evaporates, it leaves behind crystalline structures of sulfur and iron. The air isn't much safer than the ground; the hydrothermal vents frequently belch out clouds of chlorine and sulfur dioxide gas. Breathing the concentrated volcanic gases can cause immediate respiratory distress and lead to life-threatening lung inflammation within hours.

This is a place of extreme extremophiles. Scientists have found extremophiles in the region that survive in highly acidic, salty conditions, though some of the most extreme pools have been found to be completely sterile. It is a biological blueprint for what life might look like on the moons of Jupiter or Saturn. For humans, however, the heat and toxicity create a physiological ceiling that makes it impossible to stay for more than a few hours without specialized equipment.

Walking across this crust feels like walking on a thin lid over a boiling cauldron that is slowly widening as the continent of Africa splits in two.