File:Annual report of the United States Geological Survey to the Secretary of the Interior (1895) (14781039302).jpg

Identifier: annualreportofun1711geol (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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e%-ery variety of form,size, and regularity, and in California, convince him that they are the result of sur-face erosion under peculiar conditions; these conditions being a bare country and adrift soil more movable above and less movable below. Erosion removes the finertop soil, leaving it, however, in spots. The process once commenced, weeds, shrubs,and ferns take possession of these spots as the better soil, or sometimes as the driersoil, and hold them, .and by their roots retard the erosion there. In some cases adeparting vegetation—a vegetation gradually destroyed by an increasing dryness ofclimate—is an important condition. Certain it is that in all the treeless regions of California and (Oregon that ha\ e notbeen touched by the plow, the same phenomenon may be observed to ;i less extent. 1 Tho hillocks or mound forni.itions of Ban Diego, Cal.: Am. Naturalist, 187!>, p. .VS. Geology of California. Vol. I, p. 367. Abstract in Pruc, California Arad. S< i . Vol. V, p.219.
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TURNER.) TERTIARY ROCKS. 683 In California they are called hog wallows. The hog wallows of California maybo traced by insensible gradations into the larger mounds of eastern Oregon, andthese, in their turn, into the more perfect mounds of Mound Prairie; they are allevidently due to the same cause. If the mounds of Mound Prairie were a uniquephenomenon, we might resort to exceptional causes; but a phenomenon so wide-spread must be due to a widespread agent. Some information as to the agricultural value of the hog-wallowlands will be found in a report by Prof. E. A. Hilgard on the physicalgeography of the State of California.1 As a rule, where seen by the writer, these lands are uncultivated.Their huminocky nature makes the plowing of them a difficult matter,and the soil as a rule is poor. TERTIARY SEDIMENTS. The first consolidated rock seen in place by the road from Madera toDaultons is a coarse reddish sandstone, with the same pearly kaolin-like scales as are found so abundantly in th

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