Largest concentration of methane explosion craters

In July 2014, a helicopter pilot spotted a large hole in the ground on the Yamal Peninsula, northwest Siberia. At around 60 m across and 70 m deep, and clearly fresh in origin, this feature resembled an impact crater to some. However, field studies showed no signs of an impact but did reveal concentrations of methane at the bottom of the crater. Scientists now believe the hole was formed by an explosive release of methane gas that had been trapped in the permafrost. Since then a total of seven of these features have been discovered, including one crater surrounded by around 20 smaller craters. The appearance of these craters has been linked to global warming. The craters are located in the Yamalo-Nenets Autonomous Okrug of western Siberia, Russia.

The first one discovered is known as B1.