Icefall

ed surface. Perhaps the most conspicuous consequence of glacier flow, icefalls occur where the glacier bed steepens and/or narrows. The term "icefall" is formed by analogy with the word "waterfall", a similar, but much higher speed, flow phenomenon.

Most glacier ice flows at speeds of a few hundred meters per year or less. However, the flow of ice in an icefall may reach thousands of meters per year. Such rapid flow cannot be accommodated by plastic deformation of the ice. Instead, the ice fractures forming crevasses. Intersecting fractures form ice columns or seracs. These processes are imperceptible for the most part, however, a serac may collapse or topple abruptly and without warning. This behavior often poses the biggest risk to mountaineers climbing in an icefall.

Below the icefall, the glacier bed flattens and/or widens and the ice flow slows. Crevasses close and the glacier surface becomes much smoother and easier to traverse.

s. The icefall feeding the Lambert Glacier in Antarctica (photograph at left) is 7 kilometres (4.4 mi) wide and 14 kilometres (9 mi) long, even though the elevation difference is only 400 meters (1,300 ft), a little more than half that of the Roosevelt Glacier icefall.

Icefalls are climbed because of their beauty and the challenge they pose. In some cases, an icefall may provide the only feasible or the easiest route up one face of a mountain. An example is the Khumbu Icefall on the Nepalese side of Mount Everest, variously described as "treacherous" and "dangerous." It is about 5,500 metres (18,000 ft) above sea level.

References

*cite book
last = Post
first = Austin
authorlink =
coauthors = Edward R. LaChapelle
editor =
others =
title = Glacier Ice
origdate =
origyear = 1971
origmonth =
url =
format =
accessdate =
accessyear =
accessmonth =
edition = Revised edition
date =
year = 2000
month = May
publisher = University of Washington Press
location = Seattle, Washington
language =
id = ISBN 0-295-97910-0
pages = pp. 18-21
chapter =
chapterurl =
quote =