An introduction to geology

Longman, Rees, Orme, Brown, Green, & Longman, 1833 - 589 páginas

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Página 252 - Soon after the explosion commenced a number of meteorites fell to the ground over an area a mile and a half in length and half a mile in breadth. The following masses have been collected : — 1.
Página 367 - Stromboli, though at sixty miles distance, belching forth flames in an unusual manner, and with a noise which I could distinctly hear. But my attention was quickly turned from more remote to contiguous danger.
Página 389 - ... began to give way, and the greatest part of it actually fell in and disappeared in the earth. At the same time a tremendous noise was heard, resembling the discharge of the heaviest cannon. Immense quantities of volcanic substances, which were thrown out at the same time and spread in every direction, propagated the effects of the explosion through the space of many miles.
Página 192 - MP the mountain which is here composed of clinkstone, presents the columnar structure on a magnificent scale ; the columns are slightly bent and inclined. Porphyry, from an intermixture with hornblende frequently passes into sienite ; when this is the case, the latter rock generally forms the upper part of the mass. Porphyry and basalt, in enormous masses, often cover the primary mountains in the Andes. According to Humboldt, " they are arranged in regular columns, which strike the eye of the traveller...
Página 388 - Haec loca vi quondam et vasta convulsa ruina (tantum aevi longinqua valet mutare vetustas) 415 dissiluisse ferunt, cum protinus utraque tellus una foret: venit medio vi pontus et undis Hesperium Siculo latus abscidit, arvaque et urbes litore diductas angusto interluit aestu.
Página 376 - The sky was overcast at noonday with clouds of ashes ; the sun was enveloped in an atmosphere whose ' palpable ' density he was unable to penetrate ; showers of ashes covered the houses, the streets, and the fields, to the depth of several inches ; and amid this darkness explosions were heard at intervals, like the report of artillery, or the noise of distant thunder.
Página 381 - Submarine volcanoes are preceded by a violent boiling and agitation of the water, and by the discharge of volumes of gas and vapour, which take fire and roll in sheets of flame over the surface of the waves. Masses of rock are darted through the water with great violence, and accumulate till they form new islands. Sometimes the crater of the volcano rises out of the sea during an eruption. In 1783, a submarine volcano broke out near Iceland, which formed a new island ; it raged with great fury for...
Página 389 - Immense quantities of volcanic substances, which were thrown out at the same time and spread in every direction, propagated the effects of the explosion through the space of many miles. " It is estimated that an extent of ground, of the mountain itself and its immediate environs, fifteen miles long and full six broad, was by this commotion swallowed up in the bowels of the earth.
Página 314 - In viewing the position of the falls, and the features of the country round, it is impossible not to be impressed with the idea that this great natural raceway has been formed by the continued action of the irresistible Niagara, and that the falls, beginning at Lewiston have, in the course of ages, worn back the rocky strata to their present site.
Página 203 - ... which frequently form isolated caps on detached mountains. The cap of gritstone on Whin Hill, near Castleton, see Plate 4, affords an illustration of this ; and nothing is more common than to see the same bed of limestone, forming the uppermost stratum or cap of the mountains on each side of a valley. The occurrence of thick beds of basalt, divided into regular pentagonal or hexagonal columns, and disposed in ranges of vast extent and height, could not fail to arrest the attention of the most...

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