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Updated: May 5, 2025
There are also some vast piles of volcanic matter, the greater part of which is newer than the fresh-water strata, and is sometimes seen to rest upon them, while a small part has evidently been of contemporaneous origin. Of these igneous rocks I shall treat more particularly in the sequel.
"I'll show you where the car was parked." They traveled through alternate weeds and hay to where the hilltop dropped away rapidly to a valley about three hundred feet below. This marked the end of the igneous outcropping in which the lead mine was located, Rick guessed. The hill was steep, and overgrown with blackberry bushes.
Plants that serve to nourish and restore animals are themselves nourished by earth; they expand on its bosom, enlarge and strengthen at its expense, continually receiving into their texture, by their roots and their pores, water, air, and igneous matter: water visibly reanimates them whenever their vegetation or genus of life languishes; it conveys to them those analogous principles by which they are enabled to reach perfection: air is requisite to their expansion, and furnishes them with water, earth, and the igneous matter with which it is charged.
Below Sinamane's the banks are often worn down fifty feet, and composed of shingle and gravel of igneous rocks, sometimes set in a ferruginous matrix. The bottom is all gravel and shingle, how formed we cannot imagine, unless in pot-holes in the deep fissure above. The bottom above the Falls, save a few rocks close by them, is generally sandy or of soft tufa.
Thus, omitting rocks of igneous origin, it is demonstrable that all these beds of stone, of which a total of not less than seventy thousand feet is known, have been formed by natural agencies, either out of the waste and washing of the dry land, or else by the accumulation of the exuviae of plants and animals. Many of these strata are full of such exuviae the so-called "fossils."
Still further, when we look backward through the successive formations of the earth's crust we find here and there evidences in old lava flows, in volcanic ashes, and sometimes in the ruins of ancient cones which have been buried in the strata, that igneous activity such as is now displayed in our volcanoes has been, since the earliest days of which we have any record, a characteristic feature of the earth.
It is an established geological doctrine, that sedimentary strata are liable to be changed, more or less profoundly, by igneous action.
He had descended a thousand feet, he was estimating, when the black igneous rocks blazed blindingly with a reflected light like that of a thousand suns. Another hundred feet below, down a precipitous slope, was a broad table of rock. He saw it in the instant before he threw one metal-clad arm across the eye-piece of his helmet to shut out the glare.
In passing along westwards after leaving the end of the range, we came first of all on sandstone hardened by fire; then masses of granite, as if in that had been contained the igneous agency of partial metamorphosis; it had also lifted up the sandstone, so as to cause a dip to the east.
The arguments against the theory that mineral veins have been produced by the leaching of superficial igneous rocks are in part the same as those already cited against the general theory of lateral secretion. They may be briefly summarized as follows: 1. Thousands of mineral veins in this and other countries occur in regions remote from eruptive rocks.
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