Elementary Physical Geography

Elementary Physical Geography

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 edition. Excerpt: ... see them are therefore the result of deforming forces which slowly raise the mountain belt to great height, and of eroding forces which still more slowly wear down the uplifted belt by carving valleys in it. 109. Block Mountains.--In southern Oregon and the adjoining parts of California and Nevada there are many long narrow mountain ridges, extending about north and south. Each ridge is a few miles wide, ten to forty miles long, and 1000 or more feet high. The ridges are steep or cliff-like on one side, of gentler slope on the other, and are separated by flat trough-like depressions of varying breadth and depth. A general view of the country shows that the entire region was once a plain, but that it has been gradually broken into long narrow blocks, and that the blocks are tilted one way and the other, so that their uplifted edges form the mountain crests. Which block mountain is completely shown in Figure 84? How does it end? (Note: the space included in the figure is too small to show the whole length of most of the mountains; the northern part of some and the southern part of others are cut off.) Describe a large block mountain; its crest line, its cliff face, its back slope. Where could it be best ascended? Some of the ridges still preserve the form of the tilted blocks, hardly changed by weathering; their sloping backs are smooth; their cliffed fronts have little talus at the base. Others have shallow gullies worn down the back, while the cliffs are indented by ravines, and every ravine has a fanlike deposit of rock waste spread out beneath it; between the fans the cliffs have a distinct talus slope at their base. Yet the mountain blocks of Oregon are, on the whole, so little worn that they must have been broken and tilted recently in the...show more

Product details

  • Paperback | 90 pages
  • 189 x 246 x 5mm | 177g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236507282
  • 9781236507280