Glaciers or ice sheets are natural accumulations of ice possessing in-
trinsic motion, which have appeared on the Earth's land surface as a
result of the accumulation and transformation of precipitation [2].
Only a very small portion of the surface of the land is now covered by
glaciers, and at low latitudes they are found justat high elevations, on
mountain slopes. However, glaciers are known to play very important
roles in shaping the topography of the Earth, in determiningits past,
present, and future climate, and in creating the state of the world
Ocean. Recently there has also been a marked increase in the practical
value of our knowledge about glaciers, as a part of the human habitat
and as a factor affecting the economy. Interest in glaciers on other
planets is also growing. Voyages of spacecraft to Jupiter, for instance,
have shown that some Jovian satellites possess ice sheets tens of
kilometers in thickness.