The world's tallest stationary sand dunes reach 500 meters. Ground-penetrating radar revealed they're anchored by groundwater lakes hidden between dunes.
Sjoerd van Oort, CC BY-SA 3.0, via Wikimedia Commons
A desert of contradictions
The Badain Jaran Desert in northern China is hard to categorize. Spanning 49,000 square kilometers, it contains the tallest stationary sand dunes on Earth. While most dunes in the desert average around 200 meters, the mega-dunes rise to an average of 400 meters. The highest among them, Bilutu Peak, stands approximately 500 meters from base to peak, making it the tallest stationary dune in the world. These colossal sand structures are largely fixed in place, with only their surface layers shifting with the wind.
The desert's most peculiar feature is the presence of over 100 permanent, spring-fed lakes located between these giant dunes. This has earned the desert its Mongolian name, which translates to "mysterious lakes". These bodies of water range from freshwater to extremely saline. The high rates of evaporation in the arid climate cause some lakes to become hypersaline, leading to the formation of salt crusts around their edges. The varying salinity and mineral content also give some lakes distinct colors from resident algae and brine shrimp populations.
The subterranean water source
The origin of the water that sustains these lakes in a region with minimal rainfall has long been a scientific puzzle. Annual evaporation is 40 to 80 times greater than annual precipitation. Early theories pointed to local rainfall as the source, but isotopic analysis and ground-penetrating radar have shifted the consensus. The prevailing theory suggests the lakes are fed by deep groundwater that originates as precipitation and snowmelt in mountain ranges hundreds of kilometers away.
This subterranean water travels through gravel deposits and fractured rock beneath the desert, eventually emerging in low-lying areas between the dunes where the sediment becomes finer and blocks its path. This internal moisture also keeps the mega-dunes stationary. Water wicks up from the saturated base of the dunes through capillary action, and calcareous cement within the sand acts as a "skeleton," increasing the mechanical strength of the sand and allowing the dunes to reach their immense heights. Isotopic analysis shows that some of this groundwater is ancient, having been underground for thousands of years.
💡Fun Facts
The desert is one of only about 35 places on Earth that exhibit the "singing sands" phenomenon, where avalanching sand can create a loud, low-pitched rumble reaching over 105 decibels.
The name "Badain Jaran" is Mongolian for "mysterious lakes," named for the more than 100 lakes located among the dunes.
Some of the hypersaline lakes host populations of algae and brine shrimp that can turn the water pink or red.
Bilutu Peak, the tallest dune, reaches a height of about 500 meters—taller than the Empire State Building.
