United States or Liberia ? Vote for the TOP Country of the Week !
A simpler term, however, quite as distinctive, and more descriptive of their structure, is that of the stratified and massive or unstratified rocks.
Just as the different kinds of Stratified Rocks are often called Aqueous Rocks, or rocks formed by the action of water so these different kinds of Unstratified Rocks are often called Igneous Rocks, or rocks formed by the action of fire the name being taken from the Latin word for fire.
This treats of the rocks, and of their arrangement: the first embracing an account of all the important chemical elements that enter into their constitution, the minerals and organic materials that occur in their composition, and the kinds and distinguishing characteristics of those that make up the earth's surface; the second presenting the arrangement of rocks, stratified and unstratified, the structure due to deposition and other agencies, the dislocations of strata, and the consequent faults and distortions of fossils contained in them, together with considerations upon the age and chronological division of all the strata of the earth's surface.
At its mouth, near the town of Souré, and at Salvaterra, on the opposite bank, may be seen, lowest, the well-stratified sandstone, with the finely laminated clays resting upon it, overtopped by a crust; then the cross-stratified, highly ferruginous sandstone, with quartz pebbles here and there; and, above all, the well-known ochraceous, unstratified sandy clay, spreading over the undulating surface of the denudated sandstone, following all its inequalities, and filling all its depressions and furrows.
The characteristic traces left by the ice, as well known to him now as the track of the game to the hunter; the peculiar lines, furrows, and grooves; the polished surfaces, the roches moutonnees; the rocks, whether hard or soft, cut to one level, as by a rigid instrument; the unstratified drift and the distribution of loose material in relation to the ancient glacier beds, all agreed with what he already knew of glacial action.
I have repeatedly observed mountains of porphyries, more or less distinctly stratified towards their summits or on their flanks, without a trace of stratification in their central and basal parts: in most cases, I believe this is simply due either to the obliterating effects of metamorphic action, or to such parts having been mainly formed of intrusive porphyries, or to both causes conjoined; in some instances, however, it appeared to me very probable that the great central unstratified masses of porphyry were the now partially denuded nuclei of the old submarine volcanoes, and that the stratified parts marked the points whence the streams flowed.
The rock is dark grey, almost black, and of unusually hard character. It is unstratified, and so resistant that it is everywhere worn into smooth, rounded surfaces, instead of being splintered and shattered. A small, black-looking lake at the top of the pass contains to this day the bones of 500 Austrians and French who fought here in 1799. It is called the Totensee, or Dead Men's Lake.
Yet dust deposits are scant and few in great deserts such as the Sahara. The finer waste is blown beyond its limits and laid in adjacent oceans, where it adds to the muds and oozes of their floors, and on bordering steppes and forest lands, where it is bound fast by vegetation and slowly accumulates in deposits of unstratified loose yellow earth.
Some of these huge boulders were fifteen feet across, the largest of them lying in the bed of the river two miles below Depilto. Most of them were of the Depilto quartz rock and gneiss, and I saw many in the unstratified gravel near Ocotal fully eight miles from their parent rock.
A large proportion of the smaller lakes are dammed up by barriers of unstratified drift, having the exact character of the moraines of glaciers, and are termed by geologists "morainic," but some of them are true rock-basins, and would hold water even if all the loose drift now resting on their margins were removed.
Word Of The Day