Gas bubbles from waters filling crater hole on Yamal peninsula two months after volcanic-style explosion in thawing permafrost.
Floodwater from Ob River is black from spill as emergency workers flight to limit damage.
Talks also underway on gas supply route to China via Altai Mountains.
The ancient mummy of a mysterious young woman, known as the Ukok Princess, is finally returning home to the Altai Republic this month.
New cities and industries could be created from construction of high-speed railway and motorway routes spanning whole of country.
The Chinese media - and even more the country's social media - saw glamorous new first lady Peng Liyuan as the star of the summit.
Vladimir Putin surprises a female Siberian student with flowers on her 23rd birthday but also comes face to face with a woolly mammoth.
Mysterious 'gigantic' hole in remote region spotted by helicopters over gas-rich Yamal peninsula.