PIONEERING STUDIES OF LANDSCAPE EVOLUTION, CALIFORNIA VOLCANIC TABLELAND

Mid-19th Century studies of California Modoc Plateau and Cascade Arc landscape evolution include those of John Strong Newberry (1822–1892), Clarence King (1842–1901), Israel Cook Russell (1852–1906) and Joseph Silas Diller (1850–1928). In his 1857 railroad survey report [the 'Williamson expedition'], Newberry concluded that canyons crossing horsts created by Neogene–Recent basin-range faulting demonstrated the antecedence of the Pit River. Such uplift resulted in ponding of rivers in grabens, producing lakes that were the site of diatomite ['infusorial marl'] accumulation. Glaciers occupied higher regions of the Cascades and Pleistocene lakes were common along their eastern flanks. King in 1871 wrote of his discovery of several active glaciers on Mount Shasta that originally extended far into the surrounding lowlands. Russell in 1884–1885 reviewed Cascade glaciation and mapped eastern Modoc pluvial lakeshores. Diller in 1889 described several basin-range faults that accounted for recent uplift and tilting of Neogene fluvial deposits and, in associating with lava-damming, the formation of Neogene lakes in which diatomite accumulated. Erosional winnowing of agglomerates that draped uplifted land surfaces explained the abundance of boulder-strewn fields.