Snow, Ice, Avalanches, and Glaciers - Mountain Geography: Physical and Human Dimensions - page 194

melting. The meltwater then flows around the obstacle and refreezes to the downstream
side where the pressure is less (referred to as regelation ). The process is maintained by
the latent heat of fusion (given of upon refreezing), which is transmitted by conduction
from the freezing area to the melting area, where it helps maintain the melting. Regel-
ation operates only on small obstacles 1-2 m (3-7 ft) in length, however, because the
heat cannot be effectively transmitted through larger features. On larger obstacles, the
ice undergoes greater deformation and movement, probably due mainly to plastic flow,
since the ice immediately next to the obstacle must travel farther and faster in order
to keep up with the surrounding glacier mass. The larger the obstacle, the more rapid
the ice deformation and movement near the bedrock interface (Weertman 1957, 1964;
Lliboutry 1968, 1987, 1993). The processes involved in glacial flow are still a topic of
active research (Martini et al. 2001; Hooke 2005).
FIGURE 4.36 A crevasse on Collier Glacier, Three Sisters Wilderness, Oregon Cascades (downslope is
to the left). The rocky debris has fallen onto the ice from a nearby projecting ridge. (Photo by L.
W. Price.)
Structures within Glacial Ice