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Updated: September 21, 2025
The long Archaean period, into which half the story of the earth is so unsatisfactorily packed, came to a close with a considerable uplift of the land. We have seen that the earth at times reaches critical stages owing to the transfer of millions of tons of matter from the land to the depths of the ocean, and the need to readjust the pressure on the crust.
Below the plateau, slight slopes lead the eye to the last of the stratified rocks, the Tonto sandstones of the Cambrian period. These are readily distinguished, mainly by their deep buff color and the fact that generally they are found resting on the archaean or unstratified rocks, locally though incorrectly termed the granite, which makes the Inner Gorge through which the river runs.
Originally an archaean sea-bottom rock this stone lay submerged in the ocean until during the Jurassic Period, under the lateral pressure of a cooling earthcrust the table-lands and mountain-chains of Arizona rose from the seas.
From its primal source in the Archaean rock, up through all the vast series of sedimentary rocks to our own time, what vicissitudes and transformations it has passed through; how many times it has died, so to speak, and been reborn from the rocks; how many times the winds and the rains have transported it, and infused invisible, life-giving gases into it; how many of the elements have throbbed with life, climbed and bloomed in trees, walked or flown or swam in animals, or slumbered for thousands upon thousands of years beneath the great ice-sheet of Pleistocene time!
When the great procession of life first emerges out of the darkness of Archaean times, it deploys into a spreading world of strange Crustaceans, and we have the Age of Trilobites. Later there is the Age of Fishes, then of Cryptogams and Amphibia, and then of Cycads and Reptiles, and there will afterwards be an Age of Birds and Mammals, and finally an Age of Man.
The crushed and folded and dislocated strata are laid open to the weather as the horizontal strata, and as the upheaved masses of Archaean rock are not. Moreover, strata of unequal hardness are exposed, and this condition favors rapid erosion. In imagination the geologist is present at the birth of whole mountain-ranges. He sees them gestating in the womb of their mother, the sea.
In the case of our own continent we have, to begin with, about two million of square miles of Archaean rocks in detached lines and masses, rising here and there above the primordial ocean; a large triangular mass in Canada, and two broken lines of smaller masses running south from it on each side of the continent, inclosing a vast interior sea between them.
Above Grand Lake the Nascaupee River flows through an ancient valley, which is from a few hundred yards to a mile wide and cut deep into the old Archaean rocks, affording an excellent example of river erosion. The banks are of sand, and in some places clay, extending back to the foot of the precipitous hills.
Once more I do not wish to enfeeble the general soundness of this account of the evolution of life by relying on any controverted theory, and we shall find it possible to avoid taking sides. I have not referred to the climate of the earth in earlier ages, except to mention that there are traces of a local "ice-age" about the middle of the Archaean and the beginning of the Cambrian.
It would be an obvious advantage for these to retire into the interior, leaving the whole external surface free for the adjustment of the animal's relations to the outer world. Again we must refrain from following in detail the development of this new world of life which branches off in the Archaean ocean. The evolution of the Corals alone would be a lengthy and interesting story.
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