. The Yellowstone National Park : historical and descriptive : illustrated with maps, views and portraits . e definitely deter-mined, but geologists agree that they existed on every sideof the Park which itself remained buried beneath thewaters long ages after their emergence. In the course of an inconceivable extent of time, embrac-ing the Paleozoic and Mesozoic eras, these exposed areaswere denuded by the action of the elements and the result-ing detritus was spread about over the bottom of the sur-rounding seas. Not improbably chemical action, in thosetimes of intense activity of all natura
. The Yellowstone National Park : historical and descriptive : illustrated with maps, views and portraits . e definitely deter-mined, but geologists agree that they existed on every sideof the Park which itself remained buried beneath thewaters long ages after their emergence. In the course of an inconceivable extent of time, embrac-ing the Paleozoic and Mesozoic eras, these exposed areaswere denuded by the action of the elements and the result-ing detritus was spread about over the bottom of the sur-rounding seas. Not improbably chemical action, in thosetimes of intense activity of all natural agencies, may havehastened deposition from the impregnated waters and haveaided in the upbuilding of the sedimentary rocks. Fromwhatever cause, these depositions were of vast extent, theirthickness in some localities, as measured by the geologist,being several thousand feet. Possibly during all this timethere was an increasing emergence of old mountain foun-dations, bringing the outlines of the continent more andmore prominently into view. Jn geological chronology it was near the close of the O O* U?. o o o o o The Travertine Rocks. GEOLOGICAL HISTORY OF THE PARK. 191 Cretaceous Period that this long-existing condition under-went a profound change. The shrinkage of the earth inthe process of cooling had thrown a strain upon its stillweak and plastic crust which it was no longer able to with-stand. The old Archaean rocks and the vast sedimentaryaccumulations were crumpled and forced upward instupendous wrinkles, forming lofty mountain rangesabove the ancient sea. These movements may have beenvery slow, as we now reckon time, but they were rapid ina geological sense. Very interesting would it be if the geologist couldpenetrate the lavas which now cover these ancient rocks,and make for us a map of the Park region as it then may conjecture that the present surrounding mountainchains had taken form, and were probably more lofty andvery different in appearance, owing to the
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