Concern from scientists over potential danger to gas production facilities in region vital for energy supplies.
Warning of methane blasts in Kara Sea adjacent to Yamal craters caused by gas eruptions associated with melting permafrost due to global warming.
Experts to visit remote craters to solve the puzzle on their creation.
Satellites show giant hole ringed by 20 'baby craters'.
200 metres wide thermocirque seen weeks after scientists find funnel in the Yamal peninsula, caused by build up of methane.
Scientists say a 'fountain of gas' poured from jelly-like trembling earth in tundra on Belyy Island in northern Siberia.
Gas bubbles from waters filling crater hole on Yamal peninsula two months after volcanic-style explosion in thawing permafrost.
Tuim Hole first appeared 62 years ago and has sheer 120 metre cliffs reaching down to its deep turquoise waters.