Volcanos: The Character of Their Phenomena, Their Share in the Structure and Composition of the Surface of the Globe, and Their Relation to Its Internal Forces : with a Descriptive Catalogue of All Known Volcanos and Volcanic FormationsLongman, Green, Longmans, and Roberts, 1862 - Počet stran: 490 |
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aëriform appear aqueous augite Auvergne basaltic beds beneath calcareous Cantal cause cavity central clinkstone column columnar compact composed conglomerates considerable consolidation cooling crater crust crystalline crystals Darwin deposited depth distance dykes earthquakes ejected elevated erup escape Etna explosions feet felspar felspathic fissures flowed fluid force formation formed fragmentary matter fragments Geol granite greystone heat height hill horizontal hornblende Humboldt Iceland intumescent island Isles lava lava-current lava-rocks lava-streams less leucitic liquid lava mass Mezen miles mineral character Mont Dore numerous observed occasionally occasioned olivin orifice outer overlying parallel parasitical cones paroxysmal eruption peperino perhaps phenomena plutonic Ponza portion pressure prisms probably produced pumice rise Rocca Monfina rocks scoriæ scoriform side slopes Solfatara solid strata stream of lava Stromboli structure subaërial subterranean summit superficial surface temperature texture thickness tion trachytic tuff upper vapour vast vertical Vesuvius vitreous volcanic action volcanic cone volcanic eruption volcanic mountain volcanic vent
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Strana 205 - ... the larger have for the most part flat bottoms within, from which rises centrally a small, steep, conical hill. They offer, in short, in its highest perfection, the true volcanic character, as it may be seen in the crater of Vesuvius, and in a map of the volcanic districts of the Campi Phlegraei* or the Puy de Dome.
Strana 135 - Gemmellaro, who witnessed the phenomena, that the great crater in 1811 testified, by its violent detonations, that the lava had ascended to near the summit of the mountain, by its central duct. A violent shock was then felt, and a stream broke out from the side of the cone, at no great distance from its apex. Shortly after this had ceased to flow, a second stream burst forth at another opening, considerably below the first ; then a third still lower, and so on till seven different issues had been...
Strana 34 - There unquestionably exists within and below volcanic vents, a body of lava of unknown dimensions, permanently liquid at an intense temperature, and continually traversed by successive volumes of some aeriform fluid, which escape from its surface — thus presenting all the appearance of a liquid in constant ebullition.
Strana 176 - ... region one which has furnished material for a considerable number of volumes, as already mentioned. The island of Nisyros has a similar structure, the nearly circular crater being three miles in diameter and surrounded by a rim which rises from two thousand to twenty-three hundred feet above the sea. The island of St. Helena is described by Mr. Darwin as a trachytic volcano, encircled by a broken ring of basalt, measuring eight miles in diameter one way and four the other ; the internal cliff...
Strana 15 - That in which eruptions, rarely of any excessive violence, continue in a comparatively tranquil manner for a considerable time, and alternate with brief intervals of repose — phase of moderate activity.
Strana 184 - ... exposure. When reflecting on the comparatively low coasts of many volcanic islands, which also stand exposed in the open ocean, and are apparently of considerable antiquity, the mind recoils from an attempt to grasp the number of centuries of exposure, necessary to have ground into mud and to have dispersed the enormous cubic mass of hard rock which has been pared off the circumference of this island.
Strana 161 - In 1 826-7 a small cone was formed at the bottom of the crater, and, continuing in activity, had reached a height which rendered it visible from Naples in 1829, when of course it must have nearly filled up the crater. In 1830 it was 200 feet higher than the crater's rim ; and in 1831 this cavity was completely filled, and the lava-streams began to flow over it down the outer cone. In the winter of that year a violent eruption once more emptied the bowels of the mountain, and left a new crater, which...
Strana 348 - ... in their neighbourhood with their deposits. These volcanic vents differ, however, from that of Laach, in having produced leucitic lavas, and, consequently, their conglomerates are of a different character, resembling exactly the peperino of Monte Albano. Such is the rock quarried near Bell, and called bak-ofen-stein. It is in request for lining ovens, from its capacity of resistance to fire, which it owes to its being almost wholly composed of leucite in a fragmentary state. It encloses many...
Strana 352 - ... probably the mouth of one of those arched galleries which are so frequently met with under currents of lava in Iceland, Bourbon, and elsewhere. If the other extremity of the gallery communicates with the open air at a much lower level, for instance at the foot of the cone, or where the lava stream terminates in the plain below, a current of air must be continually driven through this passage from the lower to the upper extremity. In its passage, it would be thoroughly dried from the absorbent...
Strana 30 - ... consists unquestionably in the expansive force of some elastic aeriform fluid struggling to escape from the interior of a subterranean body of lava...