Satellite images have revealed more than 200 Arctic lakes that are an active source of methane emissions, according to Professor Vasily Bogoyavlensky, deputy director of the Moscow-based Oil and Gas Research Institute. The lakes, which are located in the Yamal and Gydan peninsulas, are characterised by craters or funnels in the sediment on the floor through which they release methane. The gas is produced by both microbial activity and catagenesis. The sulphur in the gas leaks results in algae flourishing in the waters, giving the lakes their distinctive blue hue. Many of the sites are located close to oil and gas deposits.