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. 



