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.
[Illustration]