Is Tunisia’s mystery lake radioactive?

A lake has mysteriously surfaced in Tunisia and no one can explain where it came from. But the more geologists learn about it, the more they think it could be radioactive.

The lake is between 10 and 18 metres deep and covers an area of around 1 hectare. It was discovered by local shepherds last month about 25 km from the city of Gafsa, in the southwest region of Tunisia in North Africa. What makes its sudden appearance especially strange is the fact that Tunisia is currently going through a severe drought. The locals have been so shocked by the lake that some have deemed it a miracle.

“After several long hours on the road without a break, I honestly thought I was hallucinating,” one of the first to spot it, Mehdi Bilel, told local journalists. “I don’t know much about science and thought it was magic, something supernatural.”

Hundreds of people have since been swimming in the lake – named ‘Lac de Gafsa’, which means Gafsa Beach – and according to, geologists have suggested that “seismic activity may have upset the water table and caused groundwater to rise to the surface”.

The first sign that something wasn’t quite with Lac de Gafsa appeared within a couple of days of its appearance – the colour of the water changed from a clean, clear turquoise to a telling murky green. “The site is certainly stunning and there are many large rocks perfect for diving, but it has become infested with green algae, meaning that the water is stagnant and conducive to diseases,” said journalist Lakhdar Souid, according to

Not only that, but the region is rich in phosphate, which is a naturally occurring form of the element phosphorus. According to Kim Willsher at the Guardian, Tunisia is the world’s fifth largest exporter of phosphate, and in this region phosphates are mined out of the rocks to obtain phosphorous compounds for use in anything from fertilisers, detergents and pesticides to nerve agents for chemical weapons, and matches. The bad news for the locals who have been swimming in Lac de Gafsa is that phosphate happens to leave behind a radioactive residue. 

About two weeks after its appearance, the Office of Public Safety in Gafsa warned the locals that it was dangerous to swim in their newly formed lake, but few have heeded the warning.

“Since there was no official ban on swimming in the lake, Tunisians continue to do so,” said Souid, according to “While the origins of this lake remains a mystery, our biggest concern right now is the quality of the water. This region is overflowing with large deposits of phosphate, which can leave behind radioactive residue so there is a real risk that this water is contaminated and carcinogenic (but) there is no security of any kind.”

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