Environmental Engineering Reference
In-Depth Information
forming under the present climatic conditions but they may still provide evidence of a
different climate in the past. Landforms of glacial erosion and deposition are some of the
best known indicators as, with careful surface mapping, they can reveal much
information about the thickness, the areal extent and direction of flow of the former ice
masses that produced the landforms. In many cases this may provide nothing more than
the conclusion of extensive ice cover. However, using the relationship between the
altitude at which ice starts to build up, and climatic conditions at present, it is possible to
infer palaeoclimates for given equilibrium lines or ice limits in the past (see Chapter 15).
In addition to landforms associated with full ice cover, we often find fossil features
produced under severe climatic conditions but without ice cover. These are termed
periglacial and form when winter temperatures fall well below freezing point and produce
ground ice. One of the best known is the ice-wedge polygon which develops either
through ground cracking at low temperature or through selective sorting of material
(Plate 9.1).
