Lake Natron is not a conventional lake. It has no outflow — water flows in from the Southern Ewaso Ng'iro
River and from mineral-rich hydrothermal hot springs fed by the nearby Ol Doinyo Lengai volcano, but water
can only leave by evaporation. In the extreme heat of the Gregory Rift — where daytime temperatures
regularly exceed 40°C — the lake loses water at a rate that concentrates whatever minerals remain behind.
Over thousands of years, this process has deposited massive quantities of natron
(hydrated sodium carbonate) and trona (sodium sesquicarbonate dihydrate) — the two salts
from which the lake takes its name.
The result is a lake so alkaline that it approaches ammonia in its corrosive properties. The pH
of Lake Natron ranges from 9 to 12 depending on water level — with the extreme end reached
during the dry season when evaporation is at its peak. Water temperatures at the surface can reach
60°C near the hydrothermal hot spring inflows. Most fish, invertebrates, and land animals
that enter the water are rapidly killed by the caustic conditions — their bodies sometimes mummified in
the lake's mineral deposits.
"The lake is beautiful and lethal in equal measure. The water that petrifies
birds is the same water that gives birth to 75% of the world's lesser flamingos. It is one of nature's
most extraordinary contradictions."
— Resilience Safaris guide, Lake Natron, 2025
The red colour that makes Lake Natron unmistakable from space is not from the minerals
themselves — it comes from life. Salt-tolerant microorganisms called halophiles,
specifically cyanobacteria (Arthrospira fusiformis) and halobacteria, thrive in the extreme
alkaline conditions. These organisms produce carotenoid pigments — red and orange
compounds — as a byproduct of photosynthesis in high-UV environments. In shallow, highly concentrated
zones, the lake turns deep crimson. Slightly deeper water appears orange or pink. The transition zones
between concentrations create the extraordinary gradient of colour visible in aerial photography.
The intensity of the colour shifts with the season. In the dry season (June–October), as water levels
drop and salt concentration peaks, the crimson is most vivid. During the rains (November–May), dilution
reduces the concentration and the colour lightens. The most spectacular red is typically seen between
August and October — coinciding with the flamingo breeding season.