Factors of Pedogenesis - Major Soil Groups of the World - page 50

Fig. 2.15 Arène in situ (below the pickaxe). It is overlain by a few decimetres of a bedded
arène, which is crowned by a coarse-bouldery fi ne material. Forez Massif. Photo : author.

Ice is semi-rigid. When a glacier encounters a bump it cannot flow over
it perfectly by flexing. It thus scrapes the downslope in the manner of
a vehicle rapidly getting over a dip in the road. More accurately, the
ice melts on the upslope of the obstacle under the effect of pressure
and a water pocket is formed downslope. On the contrary, when the
glacier plunges into a hollow, it cannot then easily straighten itself up.
In all, the glacier more or less respects the bumps and digs into the
hollows! And this is true at all scales. This results in an undulating
relief typical of glacial valleys. In particular, when the glacier moves
over soft formations, often its own moraines, it creates drumlins of size
several metres in height and a few hundred metres in length. We can
consider the Swiss Plateau is composed of thousands of drumlins or
similar forms.
The materials of moraines are a collection of coarse elements of
diverse geographic origins. They are rarely of uniform petrology.
In particle-size distribution they are equally heterogeneous because
they are accumulated without sorting. They contain boulders as well as

Scoured rocks and moraines