Differentiation of a gabbro sill in the Oregon Coast Range by crystallization-zone settling
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Exploration of the geology of the Arctic and subarctic shores of Alaska began as early as the voyages of Kotzebue and Beechey, in 1816 and 1826, and a detailed report on the vertebrate fossils found there, with a wealth of illustration, was made by Sir John Richardson in 1854, in the "Zoology of the voyage of the Herald." Nothing of importance beating on the Tertiary invertebrates of this region appears in the literature of the nineteenth century, and but little on those of the older formations.
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Since 1898 the United States Geological Survey has been carrying on systematic topographic and geologic surveys in Alaska under an appropriation made for the investigation of the mineral resources of the Territory. This work has included not only areal surveys of regions already being developed by the miner and prospector, but also explorations and investigations of regions that are little known or entirely unexplored. As a result of these explorations a network of reconnaissance traverses has been extended over a large part of Alaska, where route surveys of this character must necessarily precede more detailed topographic and geologic mapping. They serve to outline the main geographic features of the country and afford the pioneer or prospector a guide for his journeys as well as help him to select his field of operations. The present report and maps are the results of such an investigation.
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The drought 1945-56 in California affected principally the southern part of the State, and was one of a series that has been recorded in the past century. Although the precipitation in any individual year is not predictable, the pattern of alternating wetter and drier periods is consistent enough that there is clearly a- need for storing the surpluses of wetter periods to provide adequate water supplies in dry years. This cyclic storage is a basic element in the California water plan. Wherever the storage increments in wet years provide adequate supplies throughout the periods of precipitation deficiency, the effect of drought upon mankind has been overcome, or at least minimized. However, whenever the deficiency is greater than has been experienced in past droughts, some downward revisions may be necessary in previous estimates of the firm supply available for man's use.
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