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A Popular Mineralogy and Geology


A Popular Mineralogy and Geology

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    Available in PDF Format | A Popular Mineralogy and Geology.pdf | Unknown
    Katherine E. Hogan
Excerpt from book: VOLCANOES. A volcano is a mountain having an opening called a crater, through which the lava escapes. The crater is cup- shaped. In the quieter kinds the bottom of the cup melts. Then the lava boils and bubbles like any fluid, and overflows the edge. In sudden eruptions the bottom of the cup is blown violently out, scattering in all directions fragments of rock, ashes, cinders and steam. An immense amount of stifling gas is also driven out, and continues to escape long after the lava has ceased to flow. In the violent kind the explosions are often heard miles away. According to Lyell, the explosions at Tomboro, near Java, in 1815, were heard at Sumatra, nine hundred and seventy miles distant. In this dreadful visitation, so sudden and overwhelming was the eruption, that out of a population of twelve thousand souls only twenty-six remained alive. The crater of a volcano has been called a cup, but it would be more correct to call it a pipe, with the lower end closed when not in action. The pipe or tube extends downward into the bowels of the earth, no one knows how deep. It may reach the molten mass of the interior, and serve as a funnel for its escape. If, as Hopkins and Thomson affirrn, this is no molten interior, then the lava must come from some local reservoir of melted rock. Volcanoes are generally found near the sea, often on islands. There are many volcanic islands in the Pacific. The supposition is that those islands began as volcanoes beneath the sea, and have gradually grown up to the surface. In the Mediterranean new islands have been formed under the eyes of observers. '2O : -: . . A POPULAR In some of the more violent eruptions the loss of life has been great. The most memorable, perhaps, was that of Mount Vesuvius, which buried Herculaneum and Pompei...  
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Book details

  • PDF | 74 pages
  • Katherine E. Hogan
  • General Books LLC
  • Unknown
  • 9
  • Science Math
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