In northern Alaska, an amphitheater of frozen ground thaws where a northern river cuts into it, exposing walls of ice. The feature, known by scientists as “yedoma,” is the largest of its kind yet found in Alaska. A great wall of ice holds a lot of treasures from the past, which science is eager to explore.

The slope of permafrost where an 810-foot section of pipeline is secured has started to shift as it thaws, causing several of the braces holding up the pipeline to tilt and bend, according to an analysis by the Alaska Department of Natural Resources.

Thawing is impacting both above ground and underground fuel storage. They have started on a plan to empty the fuel tank and relocate it or fix the foundation.

HEALY, ALASKA—Bitter winters still dominate life in the Alaskan interior, but a practiced eye can spot the signs of a warming climate, particularly in the ground. Beneath the rolling fields of tussock scattered just north of the Alaska Range, what was once permanently frozen is starting to thaw. The impacts could ripple across the planet.

The leak was detected early Friday at the drill site CD1, 8 miles north of the village of Nuiqsut. “There are no reports of injury or environmental impact to the tundra or wildlife,” the company’s statement said. “Air quality continues to be monitored and no natural gas has been detected outside of the CD1 pad.” The gas leak happened below gravel, and its cause and scale are under investigation, Conoco said. The company said it is using natural gas detection monitors at the CD1 pad, and conducting infrared surveys from the air.