Geological history of Lake Lahontan: a Quaternary lake of northwestern Nevada (Google eBook)

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Govt. print. off., 1885 - Geology, Stratigraphic - 288 pages
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Page 194 - ... all of the perforated sort that I have seen, with one exception, were formed either of soapstone or of clay. Consisting generally of flat or rounded pieces of soapstone, irregular in shape, they vary in weight from scarcely more than an ounce to a pound and upward. The perforations are from a quarter of an inch to an inch in diameter, and are indifferently located, either in the centre or near the edge of the stone.
Page 220 - The site of the former lake then becomes a playa. A return of humid conditions would refill a basin of this character and might form a fresh-water lake, the bottom of which would be the level surface of the submerged playa. The larger lakes of the Lahontan Basin, as well as a number of less importance in eastern Nevada and southern Oregon, are without outlet. They occur in basins that in almost all cases were occupied by much larger water bodies during the Quaternary, which, like their modern representatives,...
Page 265 - ... without cataracts or rapids, the work of erosion has nearly ceased, and the marks of drift agency extend nearly or quite down to their present level. 11. It is mainly at rapids and cataracts that rivers are now deepening their beds. 12. The details that have been given enable us to form some idea of the length of time that has elapsed since the close of the drift period. The evidence on this point, rests on the assumption I have made in the preceding details, that certain old river beds that...
Page 146 - ... obsidian which occurs both as lava-flows and ejected fragments, the latter forming a light lapilli which gives a soft grey colour to the outer slopes of the craters. Fragmental material of the same nature has been widely scattered over the mountains and on the ancient moraines that occur in the Mono Lake basin, while fine dust, unquestionably derived from the same source may be traced to a still greater distance. " From the evidence given above we conclude that the strata of fine siliceous dust-like...
Page 13 - ... promises of water and shade where the experienced traveler knows there is nothing but the glaring plain. When the sun is high in the cloudless heavens and one is far out on the desert at a distance from rocks and trees, there is a lack of shadow and an absence of relief in the landscape...
Page 90 - Michigan, where they can be traced continuously for hundreds of miles. There are usually two, but occasionally three, distinct sand ridges; the first being about 200 feet from the land, the second 75 or 100 feet beyond the first, and the third, when present, about as far from the second as the second is from the first. Soundings on these ridges show that the first has about 8 feet of water over it, and the second usually about 12; between, the depth is from 10 to 14 feet. From many commanding points,...
Page 220 - ... various salts over its bed. During the rainy season the bottom of the basin is converted into a shallow lake of brine which deposits a layer of sediment; on evaporating to dryness, during the succeeding arid season, a stratum of salt is deposited, which is, in its turn, covered by sediment during the succeeding rainy season. This process taking place year after year results in the formation of a stratified deposit consisting of salts and saline clays in alternating layers. The saline deposits...
Page 74 - ... black tenacious mud, having a strong odor of sulphuretted hydrogen. When exposed to the air for some time this material loses its inky color, and shows itself to be of the same nature as the fine dust-like lapilli that form a large part of the crater walls. The organic matter impregnating these sediments is evidently derived from the millions of brine shrimps (Artemia gracilis) and. the larvse of black flies that swarm in the dense alkaline waters.
Page 247 - The sculpture of a mountain by rain is a twofold process ; on the one hand destructive, on the other constructive. The upper parts are eaten away in gorges and amphitheatres until the intervening remnants are reduced to sharp-edged spurs and crests, and all the detritus thus produced is swept outward and downward by the flowing waters and deposited beyond the mouths of the mountain gorges. A large share of it remains at the foot of the mountain mass, being...
Page 1 - Nevada; the latter, embraced almost entirely in the present Territory of Utah, occupied a corresponding position on the east side of the Great Basin, at the foot of the Wasatch Mountains. The hydrographic basins of these two water-bodies embraced the entire width of the Great Basin in latitude 41.

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