Arctic Sinkholes

Colossal explosions shake a remote corner of the Siberian tundra, leaving behind massive craters. In Alaska, a huge lake erupts with bubbles of inflammable gas. Scientists are discovering that these mystifying phenomena add up to a ticking time bomb, as long-frozen permafrost melts and releases vast amounts of methane, a potent greenhouse gas.

A pilot flying over Esieh Lake, located on the lands of the Indigenous Inupiat people, spotted something unusual on its surface.

As Alaska's permafrost thaws, Indigenous communities are looking for housing solutions, including building homes on steel sleds.