Polski
From the world, Issue 1/2026
The world’s most dangerous lakes: beauty that can kill
Jan
Toxic gases bubbling up from the depths, water corrosive as concentrated acid, boiling boils in volcanic craters or storms that turn a calm surface into a trap in a minute – these are the faces of bodies of water whose beauty goes hand in hand with real danger. Learn about the world’s most dangerous lakes and the mechanisms that make them so dangerous.
The world’s most dangerous lakes
Lake Karachay (Russia) – the world’s most radiation-contaminated lake
Located in the southern Urals, near Ozorsk, Lake Karachay became in 1951 an unofficial storage facility for liquid radioactive waste from the Mayak plant – a key component of the Soviet plutonium production program. The reservoir, covering an area of about 0.45 square kilometers, received, among other things, isotopes of cesium-137 and strontium-90. At extreme times, radioactive activity of billions of becquerels per liter was recorded there, and doses on shore could reach hundreds of X-rays per hour – a level that was lethal even with brief exposure.
In the late 1960s. In the 1970s. The drought exposed the sediment, and the wind spread radioactive dust over some 2,700 square kilometers, exposing up to 0.5 million people to its effects. It wasn’t until 2011-2016 that the lake was covered with a thick layer of concrete and soil as part of the Nuclear Safety program. Today it’s a dry concrete surface, officially safe, but radionuclides still migrate into the groundwater, posing long-term oncological and genetic risks.
Kawah Ijen (Indonesia) – one of the world’s most acidic lakes
In the crater of the active Ijen volcano in East Java is a lake of intense turquoise color. This is the result of high concentrations of iron and copper ions and suspended minerals, among other things. The greatest danger, however, lies in the chemistry: volcanic gases (e.g. SO2 and HCl) are constantly entering the water, creating an extremely acidic solution. At a pH below 0.3, the water has an aggressive effect on tissues and materials, and the concentration of dissolved substances can exceed 100 g/l.
The lake is about 36 million cubic meters in volume, and its outflow acidifies the Banyupahit River for up to 45 kilometers, exhausting the ecosystem. At the same time, Kawah Ijen remains one of the toughest places to work on Earth: hundreds of miners descend into the crater every day in thick, poisonous fumes, without adequate protection. In doing so, they carry baskets full of sulfur on their backs, weighing 70-90 kg each. Their pay usually hovers around a few-odd dollars a day, and the health cost of this work is unquantifiable. The average life expectancy of a miner working on Kawah Ijen is only 45-50 years due to chronic gas and dust poisoning.
Lake Natron (Tanzania) – one of the world’s most alkaline lakes
The Great Eastern Trench is home to Natron, a saline soda lake, where the chemistry is a product of geology and climate. The water has a strongly alkaline reaction (usually a pH of about 9-10.5, and higher in extreme conditions), as solutions rich in sodium compounds and carbonates enter the basin. Hot springs and the Ol Doinyo Lengai volcano, unique for its natrocarbonatite magma, play a significant role here. In a dry climate, evaporation exceeds inflow, so alkalinity and salinity increase, and the shallow parts of the lake heat up – locally up to about 60°C. Under such conditions, the water can irritate skin and eyes, and is an extremely hostile environment for most animals.
Natron is famous for its landscape, whose elements are the bodies of dead birds and small animals. They give the impression of being petrified. In practice, this is not immediate petrification, but preservation: solutions rich in carbonates and salt evaporate, covering the dead organisms lying near the shores with a hard, mineral shell. Over time, the deposits fix their shape, giving the effect of natural mummies that resemble museum preparations.
Despite the extreme parameters, the lake is not dead. Microorganisms that tolerate high pH and salinity live here, including cyanobacteria of the Arthrospira genus, which form dense suspensions in shallow waters and color the surface red in the dry season. They are the mainstay of the diet of lesser flamingos (Phoeniconaias minor). The birds have adaptations that allow them to function in the alkaline brine, and the harsh conditions further reduce the presence of predators, which is why Natron remains one of the most important breeding sites for flamingos in East Africa.
Dallol (Ethiopia) – the most extreme hydrothermal area on Earth
The Danakil Depression is considered one of the world’s most inhospitable regions, and Dallol is its most peculiar chemical point. It lies about 125 meters above sea level and acts like a living laboratory of geology. There is no single lake here, but a mosaic of shallow pools, seeps and mini geysers, where extreme conditions can occur simultaneously: very low pH (locally below 0), high salinity (hypersaline conditions) and elevated temperature in active outflows.
The intense colors – ranging from celadon and yellow to rusty brown – are largely the result of inorganic reactions and iron oxidation in chloride- and sulfate-rich brines. Dallol can look like a place teeming with life, while at the same time it can be almost biologically barren at times, which is why scientists are treating it as a proving ground for testing the limits of organisms’ survival in extreme chemistry.
The greatest danger is underfoot: the surface is often formed by a thin, brittle salt crust that looks like stable ground, but can crack and expose hot, corrosive brine. Gases (including CO2 and sulfur compounds) are also released from the area of springs and fumaroles, which, in windless weather, can lie low to the ground and have a suffocating effect, especially in depressions in the area.
Lake Victoria (Uganda/Kenya/Tanzania) – one of the world’s deadliest lakes
Lake Victoria covers about 68,800 square kilometers, making it Africa’s largest lake and the largest tropical lake in the world. Its location in the equatorial-tropical zone is conducive to rapid changes in weather: storms, gusty winds and high waves can occur there in a matter of minutes.
It is estimated that up to several thousand people are killed annually in such circumstances. Most are fishermen and passengers in small, overloaded boats, often going out after dark and without basic safety equipment. This lake is a reminder that nature does not always warn in advance, and that admiration of the landscape should go hand in hand with humility, knowledge and safety rules.
