This is the debris (rocks, soil, etc.) that is carried on the surface of a glacier. The debris usually originates from rockfalls as well as mixed snow and rock avalanches from the sides of steep valleys.
The thickness of the debris can range from a few millimetres to more than several metres. How debris cover is distributed over the surface of a glacier influences how the glacier’s volume changes over time. A continuous debris cover of more than five centimetres thick on the glacier surface reduces ice ablation, while a debris layer thinner than five centimetres enhances the melt rate of the glacier.
Debris-covered glaciers are extensive and common in mountainous regions such as Himalayas, Pamir, Caucasus Mountains, Alaska, Alps, and Southern Alps in New Zealand.