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 - 490 páginas |
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Términos y frases comunes
activity aëriform appear aqueous ashes augite Auvergne basaltic beds beneath Cantal cause cavity central clinkstone column columnar composed conglomerates considerable consolidation continued cooling crater crust crystalline crystals Darwin deposited depth distance dykes earthquakes ejected elevated erup eruptive vent escape Etna explosions feet felspar felspathic fissures flowed fluid force formation formed fragmentary matter fragments Geol globe granite heat height hill horizontal Humboldt Iceland internal intumescent Ischia island Isles lava lava-current lava-rocks lava-streams less leucitic Lipari liquid lava mass Mezen miles mineral character mineral matter Mont Dore numerous observed occasionally occasioned occur olivin orifice outer parallel paroxysmal eruption peperino perhaps phenomena plutonic Ponza portion pressure probably produced pumice rise Rocca Monfina scoriæ scoriform side slopes Solfatara solid strata stream Stromboli structure subaërial subterranean summit superficial surface temperature texture tion trachyte tuff upper vapour vast vertical Vesuvius violent volcanic action volcanic cone volcanic eruptions volcanic mountain volcanic vent
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Página 157 - 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...
Página 227 - ... 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.
Página 372 - ... limestone, and quader-sandstone. Some of the vents have emitted currents of augitic lava (basalt ;) others have confined themselves to the discharge of fragmentary matters. The latter principally, and in some instances almost entirely, consist of broken greywacke, slate, and sandstone, more or less affected by heat, and pulverized. It is probably owing to the clayey nature of these fragments, when reduced to great fineness, that the craters of this country have nearly, without exception, become...
Página 198 - ... 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 faces are nearly perpendicular, except that they...
Página 379 - Vivarais, where almost every possible modification of the volcanic phenomena is to be clearly traced, and on a much larger scale. In the Rhine districts, there is a comparative littleness, and an appearance as if the volcanic energy had been damped and impeded by the mass of transition and secondary strata which it had to pierce, and still more so perhaps by the fragile nature of the greywacke slate, which, shattered and pulverized by the first few aeriform explosions of every eruption, would accumulate...
Página 183 - 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...
Página 377 - I could discover no scorias amongst the ejected materials, but balls of olivine and other volcanic substances are mentioned as having been found.f This cavity, which we must suppose to have discharged an immense volume of gas, is nearly a mile in diameter, and is said to be more than one hundred fathoms deep. In the neighbourhood is a mountain called the Mosenberg, which consists of red sandstone and shale in its lower parts, but supports on its summit a triple volcanic cone, while a distinct current...
Página 78 - ... fifty to eighty feet. Another Icelandic volcano, Skaptar Jokul, burst forth in 1783, and cast out enormous streams of lava, one about fifty miles long and fifteen broad, and the other forty in length and seven wide. The thickness of these streams of molten rock was in some places more than 500 feet, and it has been calculated that the entire mass exceeds in bulk the highest mountain in Europe. One of the large volcanoes in the Sandwich Islands has, when quiet, a lake of liquid lava in the hollow...
Página 370 - ... in a fragmentary state. It encloses many small white farinaceous leucites, fragments and blocks of leucitic lava, of burnt clay-slate, and large broken plates of mica. The leucitic phonolite spoken of by Keferstein, as existing in massive beds near Reiden and Meyr, I presume to derive from this system of vents. Further to the south, and near the village of Kruft, rise three other smaller cones, covered with vegetation, and with faint traces only of craters. Other cones, and some of a- large size,...
Página 215 - Germany with scoriae two feet deep. But even more tremendous is the volcano of Mauna Loa, a huge domed-shaped mountain in Hawaii, nearly 14,000 feet above the sea, . formed chiefly by the repeated outflows of a highly liquid lava boiling up and cascading over the lips of a central vent at its summit. The phenomena of this volcano are on the most stupendous scale. The highest crater, which is circular, 8,000 feet in diameter, and 830 feet deep, is frequently filled by the welling up of the lava from...