We all know about the Greek monster Medusa, whose deadly gaze turned men to stone. That’s a legend, but a natural wonder in Africa today does just that. In North Tanzania, a unique inland lake turns wildlife to stone.
Lake Natron is a hypersaline and highly alkaline lake located in the eastern section of the volatile East African Rift. Tanzania has no less than four alkaline lakes, but Lake Natron is the most famous.
This shallow but wide lake is just three metres deep but 22km wide. It’s fed by the Southern Ewaso Ng’iro River in Kenya. During the Pleistocene period, a rare type of lava rich in sodium and potassium carbonates ran down the slopes of the Ol Doinyo Lengai volcano and into the lake.
Since the lake had no outflow and received irregular rainfall, it endured thousands of years of intense evaporation from the heat. This concentrated the trona (sodium sesquicarbonate dihydrate) and natron (hydrated sodium carbonate) in the leftover water, creating a highly toxic brine. Its average alkalinity is 10.5, its pH surpasses 12, and its water temperature ranges from 40˚ to 60˚C.
Lake Natron’s deceptively glassy surface. Photo: Shutterstock
The red color comes from bacteria
The lake’s salinity has welcomed salt-consuming, halophilic microorganisms called cyanobacteria, which need photosynthesis to survive. Generally, cyanobacteria carry different pigments. In Lake Natron, their pigment paints the water a striking red.
Somehow, a few species of fish, invertebrates, and algae manage to live in the lake. Some alkaline tilapia (a member of the cichlid family) can sustain themselves in the cooler parts of the lake.
But to some wildlife, especially birds, Lake Natron can be a death trap. The mirror-like surface tricks them into diving into the red waters for food. They drown in the toxic potion, and their outsides and insides calcify.
Wildlife photographer Nick Brandt made headlines in 2013 by staging photos of the mummified remains of the poor creatures around Lake Natron. The graphically eerie positions looked like the finger of Medusa had really touched them. The lake doesn’t quite have that instant effect.
Calcified wildlife. Photo: Shutterstock
Lesser Flamingos nest in the shallow salt water. The Ol Doinyo Lengai volcano looms in the background, right. Photo: Shutterstock
A flamingo paradise
However, one bird species has managed to make Lake Natron its home without any trouble. More than 2.5 million endangered Lesser Flamingos breed here. Seventy-five percent of the world’s population are born on its shores.
The flamingos have to contend with no predators, and they feed on the algae and cyanobacteria. They filter out the salt through the glands in the head and can deal with the scalding waters. They normally keep to the cooler areas but can wade into the hot soup if they have to. Their skin is tough enough to prevent burns.
Salt crusts on the Lake. Photo: Shutterstock
For most humans, the lake’s qualities are more suitable for the dead than the living. The ancient Egyptians used sodium carbonate and bicarbonate in the mummification process. Lake Natron would have saved pharaonic embalmers a lot of work.
People have occasionally survived the lake’s potency. In 2007, a helicopter carrying a group of wildlife videographers wishing to get footage of the flamingos crashed into the lake. It ended up nose-first in the water. Everyone survived the crash but they were in the water unprotected. It burned their eyes and skin, but they managed to drag themselves ashore. Here, some local people helped them. If they spent any longer in the lake, they would have died.
Currently, Lake Natron is under threat. The proposed construction of a hydroelectric plant on the Ewaso Ng’iro River and a soda ash plant on its shores threatens the lake’s salinity and the flamingos. While this lake remains deadly to most, it is still a vital ecosystem.
