The Staked Plains have an altitude of about 3,400 feet above sea-level, and their general slope is southeast and south. The land surface is a plain of deposition, little modified, composed of sediment carried clown by streams from the Cordilleran region to the west in Tertiary and Pleistocene tines; and is, therefore, comparatively recent. There is practically no stream (levelopmnent or drainage, and the plains are generally flat with scarcely anv irregularities except occasional depressions or sales and shallow basins containing intermittent lakes known as plavas. These range in depth fromt a few inches to 6o feet or more, are circular in contour and b)owl-shaped with smooth slopes. In area they range from a few square feet to 400 acres or more, and are (Iry most of the year, but contain water for short periods after a heavy rainfall. Having no outlets, the water is lost 1w evaporation and by percolation. Geologists advance four theories for the formation of these playas: (i) that they are solution sinks, (2) that they are remains of old water courses which have been almost filled by wind-blown material, (3) that they are due to differential settling, and (4) that they are formed by wind action. Each of these theories mav account for a greater or less number of the playas. Whatever their origin, there is no doubt but that they are at present being filled by the small amount of drainage into them and by wind action. The majority of the soils of the plains is embraced by two series, the Amarillo and the Richfield. The soil of the plavas is of the Ranmall series an(l is known as Randall clay. It is formed by sedimientation from the stirrounding soil, and varies front a mottled brown and rusty brown clay to a brown or dark-brown, drab or ash-gray clay. Frequently there is a shallow surface covering of fine sandy loam. Greenish gray, friable, calcareous clay is encountered at depths of from 2 to 6 feet. At about 20 inches the soil contains sufficient lime to effervesce with acids. The surface dries out to an ash-gray color andl often cracks to considerable depths. Randally clay is of a muckv nature andt usually contains sufficient water to stick tightly to the auger in boring, and is thus easy to remove when the neighboring soil is so dry and sandyl that a driller's spoon is necessary to obtain soil samples. MNechanical analysis shows little or no gravel, about 5 per cent of coarse sand, X per cent of medium sand, 15, per cent of fine sand, 21 per cent of silt, andl 31 per cent of clay.
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Jan 1, 1998
L D Pilipchatin + 3
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