Geological complexities aside for a moment, that’s a big pile of sodium carbonate you’re looking at.
It’s also an active volcano!
Ol Doinyo Lengai is the only active sodium carbonate (carbonatite) volcano in the world, but such volcanoes have erupted elsewhere in the past.
As I understand Rogers and Santosh, this unusual activity is possible because, while water and brine can circulate through Earth’s upper crust, the high pressures and temperatures in the lower crust support CO2-rich fluid circulation.
There’s also a middle zone that has a combination of water and CO2 fluids.
I’m not sure where this particular volcano gets its cool (literally!) lava, but this is the East African Rift, so the crust is relatively thin.
Want to climb the volcano?
Featured image: Massimo Salesi/Shutterstock
Rogers, J. J., and Santosh, M. 2004. Continents and Supercontinents. (PDF) Oxford University Press.