亚伯拉罕湖中的冰泡，加拿大艾伯塔省 Bubbles in the ice of Abraham Lake in Alberta, Canada (© robertharding/Alamy)

亚伯拉罕湖中的冰泡，加拿大艾伯塔省 Bubbles in the ice of Abraham Lake in Alberta, Canada (© robertharding/Alamy)

Frozen beauty

Located on the North Saskatchewan River, Lake Abraham is an artificial lake and Alberta's largest reservoir. Even though it's man-made, it takes on the blue color of other glacial lakes in the Rocky Mountains. In winter, the lake draws nature photographers interested not just in the wildlife and spectacular landscape, but also the lake's odd appearance when it freezes over. Bacteria on the lake bottom feed on dead organic matter and release the methane bubbles you see here. When the surface water freezes, the bubbles get trapped, creating a photographer's dream. They may be beautiful, but these frozen bubbles can be dangerous because they're highly flammable. If you happen to be lighting a match nearby, you'll want to watch out or the released methane could explode. The bubbles aren't so friendly to the environment, either; methane emissions are a major part of global greenhouse gas emissions, which contribute to climate change.