By Jamie Smith
Incredible photos show methane gas bubbles trapped below the surface of a frozen lake.
The bubbles are emitted by bacteria after they consume dead organic matter – such as plants on the lake bed – which then freeze as it reaches the lake surface in low temperatures.
The gas is considered to be harmless, but could cause an explosion if lit.
Photographer Paul Zizka, 37, took the amazing photos at Lake Minnewanka, Banff National Park, Canada and Kanaskis, Alberta, Canada.
Paul, from Canada, said: “It was a fantastic experience being able to witness this natural phenomenon with my own eyes – it’s an incredible and unique sight.
“I spent all day out there trying to capture the lakes in all their glory, with nothing but a backpack and a few snacks for company.
“The lakes are extremely deep in the middle, but towards the end where the bubbles are found it is quite shallow, so it wasn’t too dangerous to try and capture these images.”