Bulletin, Issue 7

Front Cover
University of Illinois, 1908 - Geology

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Page 106 - Reeds, including a discussion of the topographic, geologic and economic conditions controlling the supply of water for municipal and industrial purposes, with map and numerous well records and analyses. Postage 6 cents. Bulletin 6. The Geological Map of Illinois, by Stuart Weller. Second edition. Including a folded colored geological map of the State on the scale of 12 miles to the inch, with descriptive text of 32 pages.
Page 16 - ... of drift has a very variable thickness; and a mantle of drift of variable thickness cannot fail to modify the topography of the region it covers. The extent of the modification will depend on the extent of the variation. This amounts in the aggregate, to hundreds of feet. The continental ice sheet, therefore, modified the topography of the region it covered, not only by the wear it effected, but also by the deposits it made. In some places it chanced that the greater thicknesses of drift were...
Page 105 - SLIPS. [Mount each slip upon a separate card, placing the subject at the top of the second slip. The name of the series should not be repeated on the series card, but the additional numbers should be added, as received, to the first entry.] Bain, H[arry] Foster, 1872.
Page 9 - ... that the area surrounding the region where the snow accumulated would gradually be encroached upon by the spreading of the ice. Observation shows that this is what takes place in every snow field of sufficient depth.
Page 15 - But whatever the effect of the erosive work of ice action upon the total amount of relief, the effect upon the contours was to make them more gentle. Not only were the sharp hills rounded off, but even the valleys which were deepened were widened as well, and in the process their slopes became more gentle. A...
Page 76 - A little back from the coast it is slightly higher, and at a greater distance still higher. No definite degree of slope can be fixed upon as marking a baselevel. The angle of slope which would practically stop erosion in a region of slight...
Page 87 - ... for since the water did not contain the mineral matter when it entered the soil, it must have acquired it below the surface. By this means alone, areas of more soluble rock are lowered below those of less solubility.
Page 22 - In this case, some part of the load would bo dropped and over-ridden. Especially near the margin of the ice where its thickness was slight and diminishing, the ice must have found itself unable to carry forward the loads of debris which it had gathered farther back where its action was more vigorous. It will be readily seen that if not earlier deposited, all material gathered by the under surface of the ice would ultimately find itself at the edge of the glacier, for given time enough, ablation will...
Page 82 - But if, after its development, a base-level plain were elevated, the old surface in a new position would be subject to a new series of changes identical in kind with those which had gone before. The elevation would give the established streams greater fall, and they would reassume the characteristics of youth. The greater fall would accelerate their velocities ; the increased velocities would entail increased erosion ; increased erosion would result in the deepening of the valleys, and the deepening...
Page 15 - ... passed, were locally dependent on pre-existent topography, and its relation to the direction of ice movement. In general, the effort was to cut down prominences, thus tending to level the surface. But when it encountered valleys parallel to its movement they were deepened, thuft locally increasing relief.

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