Time and Change by John Burroughs — Read

If we know anything of the earth's past history, we know that the continents were long in forming, that they passed through many vicissitudes of heat and cold, of fire and flood, of upheaval and subsidence -- that they had, so to speak, their first low, simple rudimentary or invertebrate life, that they were all slow in getting their backbones, slower still in clothing their rock ribs with soil and verdure, that they passed through a sort of amphibian stage, now under water, now on dry land, that their many kinds of soils and climes were not differentiated and their complex water-systems established till well into Tertiary times -- in short, that they have passed more and more from the simple to the complex, from the disorganized to the organized. When man comes to draw his sustenance from their breasts, may they not be said to have reached the mammalian stage?

The fertile plain and valley and the rounded hill are of slow growth, immensely slow. But any given stage of the earth has followed naturally from the previous stage, only more and more and higher and higher forces took a hand in the game. First its elements passed through the stage of fire, then through the stage of water, then merged into the stage of air. More and more the aerial elements -- oxygen, carbon, nitrogen -- have entered into its constituents and fattened the soil. The humanizing of the earth has been largely a process of oxidation. More than disintegrated rock makes up the soil; the air and the rains and the snows have all contributed a share.