Physics of the Earth's CrustMacmillan and Company, 1881 - 299 Seiten |
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amount andesite anticlinal appears assumed basalt become beneath the ocean bore-hole cause centre of gravity chapter column compression condition consequently continents cooling corrugations crushing cubic cubic foot datum level density denudation deposits depression depth diminished disturbed earth earth's crust earth's surface effect elevated equal equation equilibrium eruption estimate existing extravasation fault feet fissure fluid substratum force fused geological globe greater heat Hence horizontal hypothesis igneous rock increase of temperature inequalities interior lava layer less liquid lower magma Mallet mass mean level melting temperature miles mountain neutral zone nucleus observations perature phenomena portion present produced Prof radial contraction radius rate of increase regions result rhyolite rigid rock sediment solid globe solidification specific gravity strata stratum sufficient suppose supposition theory thickness tion trachyte tract upper vapour vertical volcanic volume Waltershausen water-substance weight whole
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Seite 76 - There is no doubt that the solid parts of the earth's crust beneath the Pacific Ocean, must be denser than in the corresponding parts on the opposite side, otherwise the ocean would flow away to the other parts of the earth." And after explaining the reason for this statement he adds, " There must therefore be some excess of matter in the solid parts of the earth between the Pacific Ocean and the earth's centre, which retains the water in its place.
Seite 227 - ... crushing of portions of that shell, which compressions and crushings are themselves produced by the more rapid contraction by cooling of the hotter material of the nucleus beneath that shell, and the consequent more or less free descent of the shell by gravitation, the vertical work of which is resolved into tangential pressures and motion within the shell.
Seite 60 - Such is, on the whole, the most probable representation of the earth's present temperature, at depths of from 100 feet, where the annual variations cease to be sensible, to 100 miles; below which, the whole mass, or all, except a nucleus cool from the beginning, is (whether liquid or solid) probably at, or very nearly at, the proper melting temperature for the pressure at each depth.
Seite 76 - Geography," that the prevalence of land and water over two opposite hemispheres "proves that the force by which the continents are sustained is one of tumefaction, inasmuch as it indicates a situation of the centre of gravity of the total mass of the earth somewhat eccentric relatively to that of the general figure of the external surface — the eccentricity lying in the direction of our antipodes : and is therefore a proof of the comparative lightness of the materials of the terrestrial hemisphere.
Seite 202 - These foldings, not less than the softening of the bottom strata, establish lines of weakness or of least resistance in the earth's crust, and thus determine the contraction which results from the cooling of the globe to exhibit itself in those regions and along those lines where the ocean's bed is subsiding beneath the accumulating sediments.
Seite 145 - ... distance from it, we ought to be prepared to expect no effect whatever, or in some cases even a small negative effect. The reasoning upon which this opinion is founded, inasmuch as it must have some application to almost every investigation of geodesy, may perhaps merit the attention of the Royal Society. Although the surface of the earth consists everywhere of a hard crust, with only enough of water lying upon it to give us everywhere a couche de niveau, and to enable us to estimate the heights...
Seite 89 - At still higher temperature the water substance becomes itself dissociated into oxygen and hydrogen. But it does not follow that . the dissolved substances will be precipitated. The magma may be all the more complete the higher the temperature, because, though the bonds of affinity have fallen away, the prison-walls prevent the elements from escaping. But of all the known regions of the Universe the most unsafe to reason about is that which is under our feet.
Seite 146 - I conceive that there can be no other support than that arising from the downward projection of a portion of the earth's light crust into the dense lava; the horizontal extent of that projection corresponding rudely with the horizontal extent of the tableland...
Seite 88 - ... a certain depth ebullition would cease, and a crust be formed ; but that more water would be ready to separate to a greater depth when its affinity for the rock became lessened through the abstraction of heat, or diminution of pressure owing to the crust being partially supported by corrugation. If such was the condition of the interior in the early stages of the cosmogony, a large portion of the oceans now above the crust may once have been beneath it, and thus we gain a novel conception of...
Seite 291 - Earth have about the strength of granite at 1,000 miles from the surface, or that they have a much greater strength nearer to the surface. This investigation must be regarded as confirmatory of Sir William Thomson's view, that the Earth is solid nearly throughout its whole mass. According to this view, the lava which issues from volcanoes arises from the melting of solid rock, existing at a very high temperature, at points where there is a diminution of pressure, or else from comparatively small...