Comment: 07:38 - 08:59 (01:21)
Source: Annenberg/CPB Resources - Earth Revealed 23. Glaciers
Keywords: glacier, ice, "glacial melt", "valley glacier", "zone of accumulation", "zone of wastage", "snow line", season, firn, silt, snow, "lower elevation", "glacial retreat", snout
Our transcription: Regardless of type, all glaciers move ice from its point of origin to areas where it melts.
In a typical valley glacier, ice builds up year after year at the head of the glacier in the so-called "zone of accumulation."
Down-slope the ice melts away faster than it can build up at that lower, warmer altitude.
This is the so-called "zone of wastage."
These two zones are divided by the "snow line," which can actually be seen on some glaciers during the summer months.
Down-slope of the snow line melting snow exposes old, silty firn in the zone of wastage.
Up-slope the glacier is permanently covered with fresh white snow.
The snow line shifts up or down the surface of the glacier from year to year.
During cool years the snow line lies at lower elevations than in warm years.
If ice moves into the zone of wastage faster than it melts away, the snout of the glacier will advance farther down-slope.
But if not enough moves into the zone of wastage to compensate for melting, the snout of the glacier will retreat up-slope.
Geology School Keywords