Threat to Salekhard and Anadyr could come even sooner - by the mid-2020s - as thaw of frozen ground is forecast to have 'devastating' impact.
Scientists rush to site of latest tundra eruption - which formed a crater 50 metres deep - amid fears for homes and key industrial sites.
200 metres wide thermocirque seen weeks after scientists find funnel in the Yamal peninsula, caused by build up of methane.
When Vadim Kolpakov went on an expedition to the north of Irkutsk region, he had no inkling of the sensational discovery he was about to make.
Earth is moving as 'leaking methane gas due to global warming causes surface to bubble' in a new phenomenon.
Scientists say a 'fountain of gas' poured from jelly-like trembling earth in tundra on Belyy Island in northern Siberia.