ABSTRACT
This chapter discusses the changes in altitude with their corresponding effect on the size and shape of the habitable land masses. Owing to the action of various erosive agents which are continually removing the surface of the land and ultimately carrying the greater part of the debris into the sea, the continents are being continually worn away. During the early stage the forests were for the most part extremely like those of the present day, though a few species occur which we should associate with a warmer and moister climate. The Magdalenian period certainly represents a change from a cold, dry climate to a moister type. The snow-line in the Alps descended nearly three thousand feet, and the Arctic lemmings returned in large numbers. In the final Magdalenian period only a few of the steppe animals remain, but we have such deciduous forest animals as the squirrel, ermine and marten.
