The evolution of the earth and its inhabitants; a series delivered before the Yale chapter of the Sigma xi during the academic year 1916-1917 . ?=/ ^ /^ LANDS, GEOSYNCLINES, AND EPEIRICSEAS OF N. AMERICA. CHARLES SCHUCHERT SCALE Of 6T«TUTg MILES 100 o 200 400. FIG. 9.—Generalized map of North America in Paleozoic time, showing in whitethe lands or positive elements, in darkest shading the three geosynclines or sub-positive elements, and in lightest shading the extensive neutral medial area of thecontinent. The two heavy black lines indicate the Cincinnati and Ozark (Kan-kakee) uplifts. From th
The evolution of the earth and its inhabitants; a series delivered before the Yale chapter of the Sigma xi during the academic year 1916-1917 . ?=/ ^ /^ LANDS, GEOSYNCLINES, AND EPEIRICSEAS OF N. AMERICA. CHARLES SCHUCHERT SCALE Of 6T«TUTg MILES 100 o 200 400. FIG. 9.—Generalized map of North America in Paleozoic time, showing in whitethe lands or positive elements, in darkest shading the three geosynclines or sub-positive elements, and in lightest shading the extensive neutral medial area of thecontinent. The two heavy black lines indicate the Cincinnati and Ozark (Kan-kakee) uplifts. From the Pirsson-Schuchert Text-book of Geology, publishedby John Wiley & Sons, Inc. AND ITS INHABITANTS 63 that over the remaining small portion they vary from i to20 miles; yet the greater depths do not cover more than one-eighth of the continent, and they occur in the long and narrowtroughs of sedimentation, of which the two best known lie inthe Appalachian and Rocky Mountain regions (see Fig. 9). Eras of geological time. Now let us see how geologistsdivide this great pile of at least 53 miles of sediments andtheir included fossils. (A synopsis of geologic time is pre-sented on page 46, and in Fig. 3.) The first era, or Archeo-zoic time, with the old
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