Well, the answer is that without vegetation there is no such thing as
soil on earth anywhere. The top layer of the land in all ordinary and
well-behaved countries is composed entirely of vegetable mould, the
decaying remains of innumerable generations of weeds and grasses. Earth
to earth is the rule of nature. Soil, in fact, consists entirely of dead
leaves. And where there are no leaves to die and decay, there can be no
mould or soil to speak of. Darwin showed, indeed, in his last great
book, that we owe the whole earthy covering of our hills and plains
almost entirely to the perennial exertions of that friend of the
farmers, the harmless, necessary earthworm. Year after year the silent
worker is busy every night pulling down leaves through his tunnelled
burrow into his underground nest, and there converting them by means of
his castings into the black mould which produces, in the end, for lordly
man, all his cultivable fields and pasture-lands and meadows. Where
there are no leaves and no earth-worms, therefore, there can be no soil;
and under those circumstances we get what we familiarly know as a
desert.
The normal course of events where new land rises above the sea is
something like this, as oceanic isles have sufficiently demonstrated.
The rock when it first emerges from the water rises bare and rugged like
a sea-cliff; no living thing, animal or vegetable, is harboured anywhere
on its naked surface. In time, however, as rain falls upon its jutting
peaks and barren pinnacles, disintegration sets in, or, to speak plainer
English, the rock crumbles; and soon streams wash down tiny deposits of
sand and mud thus produced into the valleys and hollows of the upheaved
area.
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