Geology 15                                                                                          West Valley College

Geology of California                                                                                  Summer 2000

Robert Lopez


Study Questions 10: California Deserts


1)      What is a desert?  What are the three areas of California characterized as deserts? Name the natural provinces where the three principle deserts occur in California.



2)      What causes the deserts in California?  Describe the orographic effect (see fig. 6-2 page 103), and know which mountain ranges cause the rain shadows for the southern Basin and Range, Mojave, and Colorado Deserts.


3)      What happens to ascending air?  What happens to descending air?


4)      What is desert varnish, and how are petroglyphs related to desert varnish?



5)      What is desert pavement? Name two possible ways that it is formed.


6)      What are Intaglios?



7)      What are Archea?



8)      What are playas?  How are playas formed?


9)      What three conditions must be met in order to form sand dunes?



10)  What is alluvium?  What is a fan?  What is an alluvial fan (see Fig. 6-12 page 111)?


11)  What are bajadas and how are they formed?



12)  What are flash floods?  What conditions must occur in order to form flash floods?


13)  Why were lakes abundant in the Mojave and Basin and Range during the Pleistocene epoch (even Death Valley was filled by water)?



14)  What kind of erosional landform is evidence of these Pleistocene lakes (hint, one is similar to a bathtub ring)?



15)  What is tufa (not to be confused with tuff)?  What is it composed of and how does it form (see page 116)?


16)  Name at least two of the sodium borate minerals mined from the California Desert (page 119).


17)  What are some of the uses for borate minerals (page 119)?


18)  Name at least five of California’s Pleistocene Lakes located in the California Desert (Fig. 6-18, p.115).


19)  What was the name of the lake that occupied Death Valley?  What was the length and depth of this lake?


20)  When was the last time Owen’s Lake had water in it?


21)  What is the last surviving Pleistocene Lake in California’s desert – omega lake?