3.1 INTRODUCTION
At present about 10% of the Earth's surface is ice covered, but about two million years ago the Planet's climate became much colder and as a result of this the polar ice caps extended into lower latitudes to cover over 30% of the Earth's surface at their maximum. This period of time is known as the ice age. (see Diagram 3.1a).
Diagram 3.1a The ice age in Europe
As snow layers build up year after year, the
lowest layers are compacted into ice and this gradually moves
down slope under the force of gravity. Masses of ice which cover
large areas of a continent are called ice sheets whilst
those which occupy mountain valleys are called valley glaciers.
In many parts of Northern Europe, which are now free from ice,
striking features of both glacial erosion and deposition can
be seen.
