Bulletin Volume 12, Pts. 1-128

Bulletin Volume 12, Pts. 1-128

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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. 1900 edition. Excerpt: ...Heart hill, 175 feet high, in North Dakota, could be formed within a few years for any single section, or perhaps even within one summer for the great kame mentioned. Some of these gravel-depositing rivers, as shown by the widths of esker ridges and plateaus, were two to five or ten times larger than those of the moulins and rock kettles. The streams flowing in the summers from the border of the ice-sheet were doubtless of larger size and greater numbers during the final disappearance of the ice, when they formed the kames and eskers, than at any previous stage of the Glacial period. Many of the giants' kettles, if not all, are clearly referable to an early or intermediate stage. For example, they are found in Maine and in Scandinavia on coastal tracts that were depressed and submerged beneath the sea to the depths of hundreds of feet when the ice was finally melted away, as is demonstrated by the relations of the glacial drift and the overlying marine deposits, which contain molluscan shells such as now exist only in the cold waters adjoining glaciers in the arctic regions. As erosion of the bed rock cannot be supposed to have occurred at the bottom of a moulin extending so far below the sealevel, we are compelled to ascribe these glacial potholes, some of them small and others of great diameter and very deep, to some earlier part of the Ice age. I have thought them referable to the time of great continental uplift, proved by submerged valleys, when a severely wintry and snowy climate, resulting from the high land elevation, caused these great areas to become first enveloped by ice-sheets. Afterward, wherever glaciation was interrupted and again renewed, previous to the general subsidence of the land which terminated the Glacial...
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Product details

  • Paperback | 42 pages
  • 189 x 246 x 2mm | 95g
  • United States
  • English
  • black & white illustrations
  • 123683867X
  • 9781236838674