Cryoconite holes (cryo = ice and conite = dust) are vertical, cylindrical, waterfilled holes on the surface of glaciers. They contain a layer of dark colored deposits on the bottom overlain by water. The dark layer is cryoconite dust, a powdery, windblown dust made of a combination of small rock particles, soot and microbes. It may contain dust transported from far away and deposited on glaciers, snow or ice caps. The dark cryoconite dust absorbs solar radiation and melts the surrounding ice, including the ice beneath it.