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Updated: May 4, 2025
Accumulating at the average rate of one foot in ten thousand years, it would require a million years to produce a hundred feet of sediments; a hundred million to form ten thousand feet, and five hundred million to create the thickness of about ten miles of bed. At the rate of two feet in ten thousand years, the thickness accumulated would be about twenty miles.
From their bases lowlands extended westward to beyond the Missouri River. At the same time ranges were upridged out of thick Paleozoic sediments both in the Bay of Fundy region and in the Indian Territory. The eastern portion of the North American continent was now well-nigh complete. The date of the Appalachian deformation is told in the usual way.
But, by rubbing up some chalk with a brush in water and then pouring off the milky fluid, so as to obtain sediments of different degrees of fineness, the granules and the minute rounded bodies may be pretty well separated from one another, and submitted to microscopic examination, either as opaque or as transparent objects.
But the continuous deposition of strata is often interrupted by movements of the earth's crust, Old sea floors are lifted to form land and are again depressed beneath the sea to receive a cover of sediments only after an interval during which they were carved by subaerial erosion.
For millions of years it drifted aimlessly with the currents. But during all that time it was developing certain habits that it might survive more easily upon the inhospitable earth. Some of these cells were happiest in the dark depths of the lakes and the pools. They took root in the slimy sediments which had been carried down from the tops of the hills and they became plants.
Where considerable mud is being deposited along with carbonate of lime there is in process of making a clayey limestone or a limy shale; where considerable sand, a sandy limestone or a limy sandstone. CONSOLIDATION OF OFFSHORE DEPOSITS. We cannot doubt that all these loose sediments of the sea floor are being slowly consolidated to solid rock.
Every building is seen to be a remnant of once continuous beds of sediments, sand and slime on the floor of an ancient sea, and filled with the remains of animals, and every particle of the sandstones and limestones of these wonderful structures to be derived from other landscapes, weathered and rolled and ground in the storms and streams of other ages.
The passage from slate through porphyritic diorite into granite may, I think, be best explained by the increasing degree of metamorphism, and at the same time a change of the original sediments at this point; granite being the last term of metamorphism of pure clays, or clayey sandstones, while bedded diorites are similarly formed from ferruginous and calcareous slates.
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