A tear in the tundra
In the summer of 2014, helicopter pilots flying over the remote Yamal Peninsula in Siberia spotted a bizarre feature: a gaping, almost perfectly circular hole in the tundra. The crater, later designated GEC-1, was approximately 20-30 meters wide and over 50 meters deep, with sheer walls dropping into the darkness. Debris was scattered for hundreds of meters, suggesting a powerful explosion had occurred. Initial speculation ran from meteorite impacts to secret weapons tests, but scientists soon focused on a more alarming cause.
This was not an isolated event. Since the first discovery, at least 17 such craters have been identified on the Yamal and neighboring Gydan peninsulas. These "gas emission craters" (GECs) are the dramatic result of methane gas building up pressure under the frozen permafrost cap. As rising global temperatures thaw the Arctic, the previously impermeable permafrost weakens. This allows methane, both from ancient deep reserves and from the decomposition of organic matter in the soil, to accumulate in unfrozen pockets. Eventually, the pressure becomes too great, and the ground explodes with incredible force, a process some scientists have termed "cryovolcanism".
The anatomy of an explosion
The formation of a Yamal crater begins subtly. Over a period of several years, the ground surface swells into a mound, or "pingo," pushed up by the gas accumulating below. These mounds can grow to be several meters high. The trigger for the explosion is often an unusually warm summer, which thaws the permafrost "cap" from above, weakening it until it can no longer contain the pressure. The resulting blast can hurl blocks of ice and soil weighing tons hundreds of meters away.
The unique geology of the Yamal and Gydan peninsulas makes them particularly susceptible to these events. The permafrost here can be over 400 meters thick and contains widespread layers of massive ground ice. It also sits atop vast natural gas reserves. One feature is "cryopegs"—layers of unfrozen, salty water within the permafrost. Recent research suggests that warming temperatures cause fresh water from the thawing surface to move into these salty cryopegs through osmosis. This influx increases the pressure on the methane hydrates, ice-like structures trapping methane gas that lie below, destabilizing them and leading to an explosive release of gas.
The craters are ephemeral features. Within just one or two years, they fill with water and transform into lakes, becoming difficult to distinguish from the thousands of other thermokarst lakes that dot the tundra.