A New Lake behind a Ridge of Rubble

A New Lake behind a Ridge of Rubble is an original illustration set in Imja Tsho, Nepal Himalaya. It lies in the subtropics, where the climate is tundra — too cold for trees.

A long gray-green lake fills a barren high Himalayan basin behind a rough ridge of moraine. At its far end, a narrowed glacier tongue withdraws beneath steep snow peaks, while a few dark yaks traverse the angular rubble slope above the cold water.

How did a gray-green lake form directly in front of a retreating glacier?

A glacier carries rock debris along its sides and snout, then leaves that rubble behind as the ice thins and retreats. The abandoned moraine acts as a natural dam, trapping meltwater in the newly exposed basin while the glacier tongue recedes farther upslope. The unstable debris wall, growing lake, shrunken ice front, extreme altitude, and yak trail identify a moraine-dammed Himalayan glacial lake such as Imja Tsho.

Terpano is a free daily geography puzzle. You study one original illustration, place a pin on a borderless terrain map, and see how close you were. There is no account and no sign-up; progress stays in your own browser. It plays in 11 languages.