File:The continent we live on (1961) (20675718372).jpg

Title: The continent we live on
Identifier: continentweliveo00sandrich (find matches)
Year: 1961 (1960s)
Authors: Sanderson, Ivan Terence, 1911-1973
Subjects: Physical geography; Natural history
Publisher: New York : Random House
Contributing Library: New College of California
Digitizing Sponsor: Internet Archive

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cut platforms thai were once beaches, which now circle these laite areas along exact contours. There are three prominent and many subsidiary platforms around the l.ahontan basin, at 320. SU), and 110 feci, and it is ihouRht ihat these represent the ends of the three major glacial periods, in that order. F.vaporation is intense in this area and has now reduced Bonneville to the Great Salt Lake, which is only 1.^ feet deep on an average and .15 feet at its deepest. In the year 1873 it was 18 feet deeper than it is today, but so flat and shelving is the basin or rather "pan"—in which it lies that a rise of only 10 feet will spread it over an extra .SOO square miles This fact acts as regulator on and preserver of the lake; for the greater expanse of surface it presents, the more it evaporates, and it seems that its present size constitutes a balance at the current average rainfall over the years. NATURES CHEMICAL PLANT The Great Salt Lake is today slightly over 2.S per cent pure salts. This surpasses all known natural waters except for the Dead Sea in Palestine, and causes some odd and often amusing things to happen. You may enjoy morning coffee on its waters while floating beside an ordinary wood table, provided you don't create waves. However, larger birds are so buoyant on it that they find the greatest difficulty in staying upright, and after constantly capsizing they become encrusted with salts and water- logged, and cannot gel air-borne. Some of us are naturally very buoyant (I happen to be among these) and can float endlessly even in fresh water; we people should beware of such waters as these, for we have such a low Plimsoll line that it is almost impossible for us to prevent the heaviest parts of our bodies, our heads, from going downward like a lead weight. Oceanic water. even in the tropics, runs only about 3.5 per cent of salt, as opposed to more than 25 per cent here. Almost all the lakes of this province are not fresh, but neither are all of them saline: many are alkaline. Natures chemicals come in three principal forms, called acid, alkaline, and salt. The last is the stable result of neutralizing the other two by mixing. Most surface rocks contain concentrations of or are themselves basically one of these three forms. When they are eroded and washed away into lakes or the sea. many of the substances of which they are composed are dissolved in the waters. They are therefore in due course concentrated in oceans and lakes that lack outlets. (One of the ways of calculating the age of oceans is by estimating the rate of concentration of their salts.) Acid waters are rare except in swamps and bogs, which contain tannic and humic acid derived from plant roots, though there are. of course, highly acid rocks. Alkaline strata (or rocks containing dissolvable alkaline substances) are fairly common, but saline ones are com- moner due to the fact that rain water is acid (through picking up carbonic acid from the atmosphere and thus tending to neutralize the alkaline). There are. however, a surprising number of alka- line lakes in the Great Basin, and even more alkaline flats left by lakes that have completely evaporated. The great flats along- side Great Salt Lake, covering 180 square miles to a depth of four feet, are saline and composed of gleaming white crystals, mostly of calcium chloride. Left: Death Valley is an appalling desert at the southwest edge of the Great Basin in the shadow of the southern Sierra Nevadas. It is in many places guttered and sculp- tured by wind erosion.

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