peneplain.

But where will the material thus worn go? Into the sea. Going
into the ocean it will raise the level of the sea slowly but
surely. At present, for every four feet of elevation taken off
the land, there will be something like one foot rise of the
ocean level, and this rise may take only thirty thousand
years--a long time in human history, but not so long in the
history of the earth. All the time, then, that the forces of
the atmosphere are wearing down the surface of the earth to the
sea level the sea is rising and its waves are producing a plain
of marine denudation which rises slowly to meet the peneplain
which is produced by degradation. In the beginning of this
cycle, where the forces of degradation have their own way,
coarse material may be brought down by torrents from the
mountains, and the glaciers, which find their breeding place in
these high elevations, may drag down and deposit huge masses of
boulder clay. But, little by little as the mountains are
lowered, the sediments derived from them will become finer and
finer and glaciers will find fewer and fewer sources.

Not only that, but the growth of seas extending over the
continents will tend to change the climate, we shall have a
moister, more insular climate, we shall have a greater surface
of evaporation, and thus, on the whole, a more equable
temperature throughout the world. We know that, at present, the
extremes of cold and hot are found far within the interior of
the continents. Continental climates are the climates of
extremes, and on the whole extremes are hurtful to life. So
then as the forces of degradation tend to lower the continents