Notice of Prof. Jas. D. Dana's "Characteristics of Volcanoes"

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Hawaiian Gazette Company's Press, 1899 - Volcanoes - 15 pages
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Page 3 - ... floor, and terminated by a collapse which again establishes a large pit. The collapse may be accompanied by phreatic explosions, which are, however, merely incidental to the lowering of the magma level in the conduit. The essential parts of this cycle were recognized by Dana, who describes them as "(1) a rising in level of the liquid lavas and of the bottom of the crater; (2) a discharge of the accumulated lavas down to some level in the conduit...
Page 14 - ... 35 N. ; the two similar but smaller areas toward its eastern border ; the areas north of the Carolines, in the western part of the ocean ; the broad equatorial area about the Phoenix Group; the area in the South Pacific in 170 W., east of Chatham Island, and another just south of Australia. — are all so situated that no reason is apparent for referring them to a volcanic origin. Some of the areas are in the coral-island latitudes, and the supposed volcanic basis of coral islands makes a...
Page 4 - He recognizes the fact 1 that great 1 Vestiges of the Molten Globe, pp. 75, 162-167, 175, 272-278, 309, 314. heaps and columns of clouds form over an active crater, and rise at times to a height of many thousands of feet ; but accounts for these on the assumption that the heated current ascending from the active crater derives rapid accessions of air from either side, and this air, by being carried up to cold heights, yields the moisture by condensation, and so forms the column of clouds.
Page 7 - ... of some projectile action for the Kilauea lava-lakes and others in atmospheric air carried down by the descending lavas of the jets into the lava-lakes, — as the crests of waves carry down air into the sea ; and for the rest of it, or that producing the crater-fountains like those of Mount Loa, he holds that the ascensive action in the conduit, after a time of quiet, suddenly overcomes resistance or stoppages that have come to exist in the conduit at depths below, and, as a consequence, the...
Page 6 - ... must have had its initiating projectile act, and it continues for weeks and months ; and this is at variance with the evidence from Kilauea, which makes the ascensive action very gradually and quietly lifting, instead of projectile. Finally (7), the cold atmospheric air carried down into a lava-lake by the jets could generate very little projectile power. The air, on entering the lavas, would encounter a temperature near 2000 F. if not beyond it, and hence the expansion would cause expulsion,...
Page 8 - ... so unlike what had existed a few days before, may have its explanation in the dryness of the atmosphere at the time. The air is generally dry at the summit, but must have its phases of unusual dryness, during which an unusual amount of escaping moisture would, for this reason, become invisible. (6) The summit fountain is a combination of jets, each of which must have had its initiating projectile act, and it continues for weeks and months ; and this is at variance with the evidence from Kilauea,...
Page 15 - If superficially acting causes are insufficient, we are led to look deeper, to the sources of the earth's energies, or its interior agencies of development, to which the comprehensive system in its structure and physiognomy points. Whatever there is of system in the greater feature-lines, whether marked in troughs or in mountain chains or island ranges, must come primarily from systematic work within.
Page 3 - ... lavas down to some level in the conduit determined by the outbreak; (3) a downplunge of more or less of the floor of the region undermined by the discharge. Then follows another cycle : a rising again, commencing at the level of the lavas left in the conduit— that is, the lavas of the lava-column— which rising continues until the augmenting forces, from one source or another, are sufficient for another outbreak.
Page 5 - ... heated current ascending from the active crater derives rapid accessions of air from either side, and this air, by being carried up to cold heights, yields the moisture by condensation, and so forms the column of clouds. Further, he finds a cause of some projectile action for the Kilauea lava-lakes and others in atmospheric air carried down by the descending lavas of the jets into the lava-lakes, — as the crests of waves carry down air into the sea...
Page 7 - ... the moisture by condensation, and so forms the column of clouds. Further, he finds a cause of some projectile action for the Kilauea lava-lakes and others in atmospheric air carried down by the descending lavas of the jets into the lava-lakes, — as the crests of waves carry down air into the sea ; and for the rest of it, or that producing the crater-fountains like those of Mount Loa, he holds that the ascensive action in the conduit, after a time of quiet, suddenly overcomes resistance or stoppages...

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