西伯利亚巨型融陷区：正在释放远古碳的永久冻土创口
In the remote Yana Uplands of eastern Siberia, a yawning chasm known as the Batagay crater carves a scar into the taiga. Visible from satellite, this thermokarst depression—often called the 'Gateway to the Underworld'—now stretches over a kilometre long and plunges up to 100 metres deep, its sheer walls exhuming silts and ice wedges that have lain frozen for nearly 650,000 years. Its relentless expansion, accelerating to tens of metres annually, offers a dramatic window into the instability of permafrost, the frozen ground that encases a quarter of the Northern Hemisphere's land.
The crater is not a meteor scar but a self-reinforcing geological process. As rising Arctic temperatures thaw exposed icy sediments, the ground subsides, exposing fresh layers to the air and sun. This advection of heat deepens the thaw front, and the slump's concave shape traps warm air, creating a microclimate that hastens collapse. Meltwater carries away fines, leaving behind ghostly ice wedges and exposing ancient organic matter. Scientists from the Melnikov Permafrost Institute estimate the feature has already released some 170,000 tonnes of organic carbon, with much more sequestered in the sheer faces that continue to degrade each summer.
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