. The environment of Camp Grant. Fig. 20.—Map showing the extent of glaciation in North America,al Paper 106, U. S. Geological Survey. Profession- HISTORY OF THE LAND 41 All the ice-sheets were not equally extensive, and no two of themcovered exactly the same area. The region about Camp Grant was over-spread by at least two of them, and perhaps by more. That more than. lllinoiandrift sheet Glacial outwashand alluvium Fig. 21.—Sketch map showing the position of the edge of the Wisconsin ice-sheet in the vicinity of Camp Grant. Professional Paper 106, U. S. GeologicalSurvey. 42 THE ENVIRONMENT O
. The environment of Camp Grant. Fig. 20.—Map showing the extent of glaciation in North America,al Paper 106, U. S. Geological Survey. Profession- HISTORY OF THE LAND 41 All the ice-sheets were not equally extensive, and no two of themcovered exactly the same area. The region about Camp Grant was over-spread by at least two of them, and perhaps by more. That more than. lllinoiandrift sheet Glacial outwashand alluvium Fig. 21.—Sketch map showing the position of the edge of the Wisconsin ice-sheet in the vicinity of Camp Grant. Professional Paper 106, U. S. GeologicalSurvey. 42 THE ENVIRONMENT OF CAMP GRANT one ice-sheet covered the region is known in various ways, but perhapsthe simplest proof is the fact that borings for wells in the south part of thearea shown on the Kirkland map, have shown an old soil beneath one sheetof drift, and above This means that after the lower sheet ofdrift was deposited, a soil developed on it, in which vegetation , another ice-sheet buried the soil beneath another sheet of drift. Inmost places, the old soil doubtless was worn away and destroyed pastrecognition by the later ice; but it was preserved in some places. As arule, this old soil is seen only when excavations are being made, and thenonly in some places. The old soils which have become known in this re-gion, were beneath 20 to 60 or more fe
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Keywords: ., bookcentury1900, bookdecade1910, bookidenviro, booksubjectgeology
