CREVASSE ON GREAT GLACIER
Remembering that ice is a hard and brittle solid, it comes as a surprise to find that it can flow like a plastic body under the pull of gravity; but this can be easily proved. A row of stakes or of metal plates put across a glacier gradually gets out of line, the middle parts moving fastest as in a river; but the motion is very slow, even in the middle, seldom more than a few inches a day in our mountain glaciers, though some of the great Alaskan and Greenland glaciers are reported to move several feet a day and in one or two cases as much as 60 or 70 feet.
MOULIN (IN MORNING BEFORE THAW BEGINS) ROBSON GLACIER
MORAINE OF VICTORIA GLACIER
At a sudden descent, where a river would leap as a waterfall, a glacier simply breaks across in what are called “CREVASSES,” fissures which may be several feet wide and hundreds of feet long, going down to blue black depths appalling to the inexperienced climber. As the glacier advances these crevasse are bent out of shape and may be crossed by fresh crevasses, splitting up the ice into wild lumps and pinnacles called “SERACS.” Seen from a distance across some valley such an ice fall looks like a cascade or a violent rapid covered with breakers. Below these steep descents the crevasses and seracs disappear by the pressure of the moving ice and the glacier becomes a solid mass again. Small glaciers hanging from cliffs may send down avalanches of ice which combine to make a lower glacier, the masses being welded together once more. It is evident that one cause of glacier motion is the power which ice has to break and then to freeze together again.
GLACIER TABLE, NEAR TEN PEAKS, ROCKY MOUNTAINS PARK