Cryoconite

Cryoconite is powdery windblown dust made of a combination of small rock particles, soot and microbes[1] which is deposited and builds up on snow, glaciers, or ice caps.

The darkening, especially from small amounts of soot, absorbs solar radiation melting the snow or ice beneath the deposit, and sometimes creating a cryoconite hole.

[2] Cryoconite may contain dust from far away continental deserts or farmland, particles from volcanic eruptions or power plant emissions, and soot.

[3] During summer, cryoconite holes frequently contain liquid water and thus provide a niche for cold-adapted microorganisms like bacteria, algae and animals like rotifers[4] and tardigrades to thrive.

Cryoconite typically settles and concentrates at the bottom of these holes creating a noticeable dark mass.