Exploring the Sierra Juarez (Cont'd) feet above the forested plateau. No one peak rises noticeably higher than the others but from our summit we were able to see El Picacho del Diablo some sixty miles to the south. After lunch back near Laguna Hanson we turned homeward, taking the long western foothill road back to Highway #2. By 5:00 p.m. we were across the border at Tecate, having completed a very enjoyable weekend exploring by car and by foot the Sierra Juarez:

DUMONT SAND DUNES

Although one of the smaller dune fields in the Mojave Desert, the Dumont Dunes are"one of the most picturesque owing to the great bulk of the major dunes." Thus reads an article by Angus A. Mac Donald in the January 1970 issue of Mineral Information Service, a publication of the California Dlvision of Mines and Geology. Mr. MacDonald is an earth sciences instructor at Los Angeles Valley College. The Dumont Dunes are located east of State Highway 127 about 35 miles north of Baker. They are essentially non-migratory. Some of the dunes are 400 ft. from base to summit and Mr. MacDonald reports that "all of the major varieties of active dunes are found within an area of about 20 square miles." These different varieties are barchan (crescent-shaped), complex star, whaleback, tranverse, and longitudinal. The article concludes that the bulk of dune growth has taken place in the past 18,000 years and is continuing today. There are no extensive sandstone outcroppings in this area (unlike the Sahara) so that some other type of sand source musy be developed. The author of the artic1e hypothesizes that the dunes first began forming when the 1akes in this area during Pleistocene times (Lake Man1y in Death Val1ey and Lake Dumont in Silurian Valley) would dry up during integlacial periods. This would leave sand along their edges (southern edge of Lake Manly) which was then available for transport by wind. Contemporary sources of sand, in addition to the sediments of Lake Dumont, are the short-lived creeks and rivers in the region such as, Amargosa River, Salt Creek, and Kingston Wash. The author feels that wind records from the now abandoned Silver Lake CAA station and his examination of individual grains of sand in the various parts of the dunes indicate, in support of his theory, that the majority of dune-building, winds are from the west with winds from the north and south of secondary importance.

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