Identifier: sixthannualrepor00geol (find matches)
Title: Sixth annual report of the United States geological survey of the Territories, embracing portions of Montana, Idaho, Wyoming, and Utah : being a report of progress of the explorations for the year 1872
Year: 1873 (1870s)
Authors: Geological and Geographical Survey of the Territories (U.S.) Hayden, F. V. (Ferdinand Vandeveer), 1829-1887
Subjects: Botany Zoology Meteorology
Publisher: Washington : G.P.O.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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e entire valley has beencarved out of the massive rocks which must have been far more extensivethan we see them at present. From the source of this branch to the en-trance into the main valley, a distance of fifteen miles, a mass of rock-ma-terials has been worn out one-fourth of amilein width, almost fifteen milesin length, and of a thickness at least equal to the summits of the highestpeaks, some of which are 3,000 feet above the valley below. We cannotnow estimate how much of the surface may have been wasted away,but the evidence is clear that no inconsiderable portion has beenremoved. When the limestones are exposed underneath the conglom-erates on one side of the canon, the corresponding strata are seen onthe opposite side. The conglomerates are very nearly or quite hori-zontal, the lower portion adapting itself to the irregular surface of thelimestone like any other sedimentary deposits. This valley or canon isonly an illustration of many others. I have no doubt that the Carbon-
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GEOLOGICAL SUEVEY OF THE TERRITOEIES. 47 iferons limestones underlie the greater portion of the country east ofthe Grand Canon and the lake, extending over to the sources of ClarksFork, Stinkingwater, and other streams. This enormous thickness ofconglomerate once extended all over it in one unbroken mass, but sincethe subsidence of the waters the volcanic mass has been cleft downinto the underlying beds of limestone in every direction, forming someas remarkable scenery as there exists on our continent. Mr. ITolmes,the artist of the expedition, has sketched many natural sections show-ing most clearly the relations of the conglomerates with the limestonesbelow, and presenting in detail the singularly unique forms which areproduced abundantly by the meteoric forces. Mingled with the conglom-erates are vast irregular masses of trachyte, the result of repeated over-flows from the craters and fissures. In many cases the nucleus of thecones or peaks are massive trachyte. There are also alter

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