The Batagay crater was first detected on satellite images in 1991, but likely formed in the 1970s. (Image credit: Imagery © 2024 Airbus, CNES/Airbus, Landsat/Copernicus, Maxar Technologies, Map Data © 2024.)
The “Gateway to the Underworld” is a huge, growing crater in the permafrost of Siberia. Officially known as the Batagaysky Crater (also known as Batagayka), or mega-sinkhole, it formed when part of the slope of the Yana Upland collapsed in the 1970s. However, the crater went unnoticed until 1991, when satellite images showed a rounded rock rising above a vast depression in the frigid landscape.
The Batagay crater is the largest megadepression in the world, measuring 990 metres (3,250 ft) wide as of 2023. The cliff at its top, or escarpment, is 55 metres (180 ft) high.
When the sluice formed, it exposed layers of permafrost that had been frozen for 650,000 years—the oldest permafrost in Siberia and the second-oldest in the world, behind only relict ground ice in the Yukon, Canada, which is about 740,000 years old. Recent research has shown that the sluice is expanding by about 1 million cubic meters (35 million cubic feet) each year, digging deeper and exposing new layers of ancient permafrost.
According to the 2024 study, the top wall of the sluice is also retreating at a rate of 12 meters (40 feet) per year due to melting permafrost, releasing large amounts of ice and sediment into the crater. Some of this melted material may remain in the crater, but sediment and ice are also washed into the Batagay River valley, located at the far end of the sluice, the researchers noted in their study.
The permafrost in the region is 80 percent ice, and that's likely what caused the initial collapse of the hillside, Thomas Opel, a paleoclimatologist at the Alfred Wegener Institute in Germany who has studied the “gateway to the underworld,” previously told Live Science.
The gate is located in an area of larch and birch forests that have been deforested since the 1940s. The deforestation led to the rapid erosion of the topsoil and the exposure of the underlying permafrost, which – due to its icy composition – melted faster than if it had been more heavily rain-saturated. The significant melting in the following decades caused the erosion and collapse of the hillside, Opel commented.
The frozen soils exposed along the headwall of the sluice are helping researchers piece together a picture of past climates. Siberia has very few ancient permafrost layers available for study, so the Batagay megadepression is an important laboratory for paleoclimate research groups, Opel said.
The gateway also offers scientists the opportunity to study ancient plant and animal life. In 2018, for example, researchers found a 42,000-year-old intact Pleistocene horse foal (Equus caballus lenensis) sticking out of the headwall of a megaslide. While older layers of permafrost may not contain such well-preserved specimens, Opel suggested, ancient DNA could likely be found there.
“Of course, there is more to come,” Opel added.
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