Found 30 metres underground at a coal mine, they're dubbed 'Jurassic pearls' or the marbles of a Siberian colossus. 

Same phenomenon of discharge of gas hydrates 'led to crater formation in Russia and disappearance of ships in Atlantic'.

The sensational discovery could lead to a much clearer understanding of a blast which was 1,000 times more powerful than the Hiroshima bomb.

As usual there is outlandish speculation about an alien visit, but there is genuine puzzlement and disagreement among experts over the mystery object.

Haunting beauty of massive hole as scientists examine frozen lake formed after giant blowout.

Scientists intrigued over 'space rock' found 35 years ago, before being dumped in a geologist's fish tank.

Scientists give startling theory for 1908 Tunguska Event in Siberia which had force of 185 Hiroshima bombs.

Mysterious 'gigantic' hole in remote region spotted by helicopters over gas-rich Yamal peninsula.

Whisky proves popular in the land of vodka.