Report on the Geology of the High Plateaus of Utah, with Atlas

Report on the Geology of the High Plateaus of Utah, with Atlas

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 edition. Excerpt: ...IMPERFECT CHARACTER OF TEE PREMISES. 139 quartz-propylites as contributing their quota of support to the theory, we may still hold that they are not necessarily in conflict with it. There is another conceivable mode in which the law here propounded theoretically may be modified in a manner which would yield results differing from the standard sequence to which it has been applied and give a somewhat different but still a definite succession. It might be affected by the depth at which the seat of volcanic activity is located, and also by the value of the mean density of the overlying rocks. Assuming our theory to be correct, let us call the depth at which Richthofens succession becomes the normal one, unity. Suppose the depth to be considerably greater than unity, the melting temperature of the acid rocks would then be greater on account of the increased pressure. Recurring to the graphic diagram, the effect of this modification would be to transfer the intersection of the fusion and density curves to the left or toward the basic end of the scale, and rocks more basic than propylite would be first erupted and the succession would be more or less modified. The nature of the modification will readily appear by treating the modified diagram in the same manner as has been employed already. Or suppose the depth of eruptive activity to be less than the assumed unity: the intersection of the two curves would be transferred to the right and an inverse series of modifications would result. On the assumption that the secular cooling of the earth is gradually sinking the seat of volcanicity to lower horizons, it would follow that a corresponding modification is secularly proceeding in the normal order of succession in volcanic eruptions. This theory...show more

Product details

  • Paperback | 122 pages
  • 189 x 246 x 7mm | 231g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236527976
  • 9781236527974