Scientists are puzzling to explain the tremor, 8.3 on the Richter scale, by far the largest since records began.
Mysterious 'gigantic' hole in remote region spotted by helicopters over gas-rich Yamal peninsula.
Satellites show giant hole ringed by 20 'baby craters'.
Haunting beauty of massive hole as scientists examine frozen lake formed after giant blowout.
Same phenomenon of discharge of gas hydrates 'led to crater formation in Russia and disappearance of ships in Atlantic'.