,u4 ,s4 ,dep>tm5t ( ! ,int]ior _/ ,u4   
,s4 ,geological ,survey                 
,des]ts3                                
,geology & ,res\rces                    
by ,a4 ,s4 ,walk]    ,illu/ration3      
,great ,s& ,dunes ,national ,monum5t1   
,colorado 7photograph  by ,john ,kei?74 
,beauty is be=e me    ,& beauty beh9d   
me1    ,above & bel[ me hov]s !         
beautiful1    ,i am surr\nd$ by x1    ,i
 am imm]s$ 9 x4    ,9 my y\? ,i am aw>e 
( x1    ,& 9 old age    ,i %all walk    
quietly    ,! beautiful trail4      f a 
,navajo b5$ictory *ant describ+ ! des]t 
,illu/ration3 ,cacti dom9ate ! ,sonoran 
,des]t vegetation ne> ,tucson1  ,arizona
 7photograph by ,pet] ,kresan74         
,:at ,is a ,des]t8      ,approximately  
"o-?ird ( ! ,e>?'s l& surface is des]t1 
arid l&  ) meag] ra9fall t supports only
 sp>se vegetation & a limit$  population
 ( p & animals4 ,des]ts--/>k1 sometimes 
my/]i\s  worlds--h be5 portray$ z       
fasc9at+ environm5ts ( adv5ture &       
exploration f n>ratives su* z t (       

,lawr5ce ( ,arabia to movies  su* z     
8,dune40 ,^! arid regions are call$     
des]ts because !y are  dry4 ,!y may be  
hot1 !y may be cold4 ,!y may be regions 
( s& or  va/ areas ( rocks & gravel     
pepp]$ ) occasional plants4 ,b  des]ts  
are always dry4    ,illu/ration3        
,ripples on a dune 9 ! ,gran ,desi]to1  
,mexico  7photograph by ,pet] ,kresan74 
,des]ts are natural laboratories 9 :i*  
to /udy ! int]actions (  w9d & sometimes
 wat] on ! arid surfaces ( planets4 ,!y 
conta9  valuable m9]al deposits t 7 =m$ 
9 ! arid environm5t or  t 7 expos$ by   
erosion4 ,because des]ts are dry1 !y are
 ideal  places = human artifacts &      
fossils to be pres]v$4 ,des]ts are also 
fragile environm5ts4 ,! misuse ( ^! l&s 
is a s]i\s & gr[+  problem 9 p>ts ( our 
_w4    ,illu/ration3 ,,di/ribution ,,(  
,,non-,,pol> ,,arid ,,l& 7aft] ,meigs1  
#aiec7                                  
,high]-resolution map    ,!re are almo/ 
z _m def9itions ( des]ts &              
classification  sy/ems z !re are des]ts 

9 ! _w4 ,mo/ classifications rely on  "s
 comb9ation ( ! numb] ( days ( ra9fall1 
! total am\nt (  annual ra9fall1        
temp]ature1 humidity1 or o!r factors4 ,9
 #aiec1  ,pev]il ,meigs divid$ des]t    
regions on ,e>? into ?ree categories    
accord+ to ! am\nt ( precipitation !y   
receiv$4 ,9 ?is n[  widely accept$      
sy/em1 extremely arid l&s h at lea/ #ab 
consecutive mon?s )\t ra9fall1 arid l&s 
h less ?an #bej  millimet]s ( annual    
ra9fall1 & semi>id l&s h a mean annual  
precipitation ( betwe5 #bej & #ejj      
millimet]s4 ,arid & extremely  arid l&  
are des]ts1 & semi>id grassl&s g5]ally  
are ref]r$ to  z /eppes4                
,illu/ration3 ,gran ,desi]to ( !        
,sonoran ,des]t1 ,mexico4 ,surr\nd+  !  
d>k #be-kilomet]-long & #e-kilomet]-wide
 ,si]ra del ,ros>io  m\nta9s 7upp] "r7  
are dunes & %eets ( s&4                 
,h[ ! ,atmosph]e ,influ5ces ,aridity    
,we live at ! bottom ( a gase\s         
envelope--! atmosph]e--t is b\nd        
gravitationally to ! planet ,e>?4 ,!    

circulation ( our atmosph]e  is a       
complex process because ( ! ,e>?'s      
rotation & ! tilt ( its  axis4 ,! ,e>?'s
 axis is incl9$ #bc f ! ecliptic1 !     
plane (  ! ,e>?'s orbit ar\nd ! ,sun4   
,due to ?is incl9ation1 v]tical rays  ( 
! ,sun /rike #bc ,n4 latitude1 ! ,tropic
 ( ,canc]1 at summ]  sol/ice 9 late     
,june4 ,at w9t] sol/ice1 ! v]tical rays 
/rike #bc  ,s4 latitude1 ! ,tropic (    
,capricorn4 ,9 ! ,nor!rn ,hemisph]e1 !  
summ] sol/ice day has ! mo/ daylight    
h\rs1 & ! w9t] sol/ice  has ! fewe/     
daylight h\rs ea* ye>4 ,! tilt ( ! axis 
all[s  diff]5tial heat+ ( ! ,e>?'s      
surface1 :i* causes seasonal  *anges 9 !
 global circulation4    ,illu/ration3 ,!
 circulation patt]n ( ! ,e>?'s          
atmosph]e4 ,mo/  ( ! nonpol> des]ts lie 
)9 ! two trade w9ds belts4    ,on a     
planet>y scale1 ! circulation ( air     
betwe5 ! hot ,equator &  ! cold ,nor? & 
,s\? ,poles creates pressure belts t    
influ5ce  wea!r4 ,air w>m$ by ! ,sun    
rises at ! ,equator1 cools z x moves    

t[>d ! poles1 desc5ds z cold air ov] !  
poles1 & w>ms aga9  z x moves ov] !     
surface ( ! ,e>? t[>d ! ,equator4 ,?is  
simple patt]n ( atmosph]ic convection1  
h[ev]1 is complicat$ by !  rotation ( ! 
,e>?1 :i* introduces ! ,coriolis        
,effect4    ,to appreciate ! orig9 ( ?is
 effect1 consid] ! foll[+4 ,a /ick      
plac$ v]tically 9 ! gr\nd at ! ,nor?    
,pole w\ld simply turn  ar\nd z ! ,e>?  
rotates4 ,a /ick at ! ,equator w\ld move
 9 a  l>ge circle ( almo/ #dj1jjj       
kilomet]s ) ! ,e>? z x rotates4    ,!   
,coriolis ,effect illu/rates ,newton's  
fir/ law ( motion--a body 9  motion w   
ma9ta9 its spe$ & direction ( motion    
unless act$ on  by "s outside =ce4 ,?us1
 a w9d travell+ nor? f ! equator  w     
ma9ta9 ! velocity acquir$ at ! equator  
:ile ! ,e>? "u  x is mov+ sl[]4 ,?is    
effect acc\nts = ! g5]ally ea/-we/      
direction ( w9ds1 or /reams ( air1 on ! 
,e>?'s surface4 ,w9ds  bl[ betwe5 areas 
( diff]5t atmosph]ic pressures4    ,!   
,coriolis ,effect influ5ces !           

circulation patt]n ( ! ,e>?'s           
atmosph]e4 ,9 ! zone betwe5 ab\t #cj ,n4
 & #cj ,s41 ! surface air  fl[s t[>d !  
,equator & ! fl[ al(t is polew>d4 ,a    
l[-pressure  area ( calm1 light v>iable 
w9ds ne> ! equator is kn[n to m>9]s  z !
 doldrums4    ,ar\nd #cj ,n4 & ,s41 !   
polew>d fl[+ air beg9s to desc5d t[>d  !
 surface 9 subtropical high-pressure    
belts4 ,! s9k+ air is  relatively dry   
because its moi/ure has already be5     
releas$ ne> !  ,equator above ! tropical
 ra9 =e/s4 ,ne> ! c5t] ( ?is            
high-pressure zone ( desc5d+ air1 call$ 
! 8,horse ,latitudes10 !  w9ds at !     
surface are weak & v>iable4 ,! "n = ?is 
area is  believ$ to h be5 giv5 by       
colonial sailors1 :o1 becalm$ sometimes 
at ^! latitudes :ile cross+ ! oceans )  
horses z c>go1 7  =c$ to ?r[ a few      
horses ov]bo>d to cons]ve wat]4    ,!   
surface air t fl[s f ^! subtropical     
high-pressure belts  t[>d ! ,equator is 
deflect$ t[>d ! we/ 9 bo? hemisph]es by 
! ,coriolis ,effect4 ,because w9ds are  

nam$ = ! direction f  :i* ! w9d is bl[+1
 ^! w9ds are call$ ! nor!a/ trade  w9ds 
9 ! ,nor!rn ,hemisph]e & ! s\!a/ trade  
w9ds 9 !  ,s\!rn ,hemisph]e4 ,! trade   
w9ds meet at ! doldrums4 ,surface w9ds  
kn[n z 8we/]lies0 fl[ f ! ,horse        
,latitudes t[>d ! poles4  ,! 8we/]lies0 
meet 8ea/]lies0 f ! pol> highs at ab\t  
#ej-fj  ,n4 & ,s4    ,ne> ! gr\nd1 w9d  
direction is affect$ by friction & by   
*anges  9 topography4 ,w9ds may be      
seasonal1 sporadic1 or daily4 ,!y range 
f g5tle breezes to viol5t gu/s at spe$s 
great] ?an #cjj  kilomet]s_/h\r4        
,illu/ration3 ,^! dunes 9 ! ,algodones  
,s& ,sea ( s\!a/]n  ,cali=nia move z mu*
 z #e met]s p] ye>4 ,! dunes 9 ?is      
photograph1 look+ s\?1 move t[>d ! ea/  
7left7 7photograph by  ,pet] ,kresan74  
,illu/ration3 ,se>les ,lake1 ,cali=nia  
7photograph c\rtesy (  ,k]r-,mc,gee1    
,inc474                                 
,:]e ,des]ts ,=m      ,dry areas creat$ 
by global circulation patt]ns conta9 mo/
 ( !  des]ts on ! ,e>?4 ,! des]ts ( our 

_w are n re/rict$ by  latitude1         
longitude1 or elevation4 ,!y occur f    
areas close to !  poles d[n to areas ne>
 ! ,equator4 ,! ,p's ,republic ( ,*9a   
has  bo? ! highe/ des]t1 ! ,qaidam      
,depression t is #b1fjj met]s  above sea
 level1 & "o ( ! l[e/ des]ts1 ! ,turpan 
,depression  t is #aej met]s bel[ sea   
level4    ,des]ts are n conf9$ to ,e>?4 
,! atmosph]ic circulation patt]ns  ( o!r
 t]re/rial planets ) gase\s envelopes   
also dep5d on !  rotation ( ^? planets1 
! tilts ( _! axes1 _! di/ances f  !     
,sun1 & ! composition & d5sity ( _!     
atmosph]es4 ,except  = ! poles1 ! entire
 surface ( ,m>s is a des]t4 ,v5us also  
may  support des]ts4    ,illu/ration3 ,!
 ,g>lock fault1 ne> ! bottom ( ?is      
,l&sat image1  is g5]ally consid]$ to be
 ! geologic bord] betwe5 ! ,mojave      
,des]t 9 ! s\? & ! ,great ,bas9 ,des]t 9
 ! nor?4 ,! ,great  ,bas9 conta9s m ?an 
#aej discrete des]t bas9s sep>at$ by m  
?an #afj m\nta9 ranges4                 
,types ( ,des]ts      ,des]ts are       

classifi$ by _! geographical location & 
dom9ant  wea!r patt]n z trade w9d1      
midlatitude1 ra9 %ad[1  coa/al1 monsoon1
 or pol> des]ts4 ,=m] des]t areas       
pres5tly  9 non>id environm5ts are      
paleodes]ts1 & extrat]re/rial  des]ts   
exi/ on o!r planets4                    
,trade w9d des]ts    ,! trade w9ds 9 two
 belts on ! equatorial sides ( ! ,horse 
,latitudes heat up z !y move t[>d !     
,equator4 ,^! dry w9ds  dissipate cl\d  
cov]1 all[+ m sunlight to heat ! l&4    
,mo/ (  ! major des]ts ( ! _w lie 9     
areas cross$ by ! trade w9ds4  ,! _w's  
l>ge/ des]t1 ! ,sah>a ( ,nor? ,africa1  
:i* has  exp]i5c$ temp]atures z high z  
#eg ,c1 is a trade w9d des]t4           
,midlatitude des]ts    ,midlatitude     
des]ts occur betwe5 #cj & #ej ,n4 & ,s41
 polew>d ( !  subtropical high-pressure 
zones4 ,^! des]ts are 9 int]ior dra9age 
bas9s f> f oceans & h a wide range (    
annual temp]atures4 ,!  ,sonoran ,des]t 
( s\?we/]n ,nor? ,am]ica is a typical   
midlatitude  des]t4                     

,ra9 %ad[ des]ts    ,ra9 %ad[ des]ts are
 =m$ because tall m\nta9 ranges prev5t  
moi/ure-ri* cl\ds f rea*+ areas on !    
lee1 or protect$ side1  ( ! range4 ,z   
air rises ov] ! m\nta91 wat] is         
precipitat$ &  ! air loses its moi/ure  
cont5t4 ,a des]t is =m$ 9 ! leeside     
8%ad[0 ( ! range4    ,illu/ration3 ,!   
,sah>a ( ,africa is ! _w's l>ge/ des]t4 
,x  conta9s complex l9e> dunes t are    
sep>at$ by almo/ #f kilomet]s  7,skylab 
photograph74    ,illu/ration3 ,a r>e ra9
 9 ! ,t5gg]1 a midlatitude des]t (      
,*9a1 exposes ripples & a small bl[\t on
 ! left4 ,w9ds w  %ortly cov] or remove 
^! features4    ,illu/ration3 ,?is      
,l&sat image %[s ! ,turpan ,depression 9
 !  ra9 %ad[ des]t ( ! ,tian ,%an (     
,*9a4 ,a s& sea is 9 ! l[]  c5t] on !   
"r1 b des]t pavem5t1 gray 9 color1      
dom9ates ?is  des]t4 ,! few oases 9 !   
des]t & ! vegetation 9 ! m\nta9s  at !  
top are 9 r$4 ,a blanket ( sn[ sep>ates 
! vegetation 9 !  ,tian ,%an f ! ra9    
%ad[ des]t4                             

,coa/al des]ts    ,coa/al des]ts g5]ally
 are f\nd on ! we/]n edges ( cont95ts   
ne> ! ,tropics ( ,canc] & ,capricorn4   
,!y are affect$ by cold  ocean curr5ts t
 p>allel ! coa/4 ,because local w9d     
sy/ems  dom9ate ! trade w9ds1 ^! des]ts 
are less /able ?an o!r  des]ts4 ,w9t]   
fogs1 produc$ by upwell+ cold curr5ts1  
frequ5tly  blanket coa/al des]ts & block
 sol> radiation4 ,coa/al des]ts are     
relatively complex because !y are at !  
juncture ( t]re/rial1  oceanic1 &       
atmosph]ic sy/ems4 ,a coa/al des]t1 !   
,atacama ( ,s\?  ,am]ica1 is ! ,e>?'s   
drie/ des]t4 ,9 ! ,atacama1 measurable  
ra9fall--#a millimet] or m ( ra9--may   
occur z infrequ5tly z once  e #e-bj     
ye>s4    ,illu/ration3 ,cresc5t-%ap$    
dunes are common 9 coa/al des]ts su*  z 
! ,namib1 ,africa1 ) prevail+ on%ore    
w9ds4 ,l[ cl\ds cov]  p>ts ( ! ,namib 9 
?is space %uttle photo4    ,illu/ration3
 ,high dunes ( ! ,namib ,des]t ne>      
,sossus ,vlei  7photograph by ,georg    
,g]/]74    ,illu/ration3 ,morn+ fog     

moi/5s ! dunes ( ! ,namib coa/al  des]t 
7photograph by ,georg ,g]/]74           
,monsoon des]ts    8,monsoon10 d]iv$ f  
an ,arabic ^w = 8season10 ref]s to a w9d
  sy/em ) pron\nc$ seasonal rev]sal4    
,monsoons develop 9 response  to        
temp]ature v>iations betwe5 cont95ts &  
oceans4 ,! s\!a/  trade w9ds ( ! ,indian
 ,ocean1 = example1 provide heavy summ] 
ra9s  9 ,india z !y move on%ore4 ,z !   
monsoon crosses ,india1 x loses  moi/ure
 on ! ea/]n slopes ( ! ,aravalli ,range4
 ,! ,raja/han  ,des]t ( ,india & ! ,?>  
,des]t ( ,paki/an are p>ts ( a monsoon  
des]t region we/ ( ! range4             
,illu/ration3 ,! ,indus ,riv] floodpla91
 l[] left1 is ! we/]n  bord] ( ! ,?>    
,des]t4 ,?is ,l&sat image ( ! monsoon   
des]t  %[s small pat*es ( s& %eets 9 !  
upp] "r1 ) ?ree types  ( dunes2 "s dunes
 are almo/ #c kilomet]s long4           
,pol> des]ts    ,pol> des]ts are areas )
 annual precipitation less ?an #bej     
millimet]s & a mean temp]ature dur+ !   
w>me/ mon? ( less ?an  #aj ,c4 ,pol>    

des]ts on ! ,e>? cov] ne>ly #e million  
squ>e  kilomet]s & are mo/ly b$rock or  
gravel pla9s4 ,s& dunes are n  prom95t  
features 9 ^! des]ts1 b sn[ dunes occur 
commonly 9  areas :]e precipitation is  
locally m abundant4    ,temp]ature      
*anges 9 pol> des]ts frequ5tly cross !  
freez+ po9t  ( wat]4 ,?is 8freeze-?aw0  
alt]nation =ms patt]n$ textures on !    
gr\nd1 z mu* z #e met]s 9 diamet]4      
,illu/ration3 ,! ,dry ,valleys (        
,ant>ctica h be5 ice-free =  ?\s&s (    
ye>s 7c\rtesy ( ,,usgs ,image ,process+ 
,facility1  ,flag/aff1 ,arizona74       
,paleodes]ts    ,illu/ration3 ,?is a]ial
 photograph ( ! ,nebraska ,s& ,hills    
paleodes]t %[s a well-pres]v$           
cresc5t-%ap$ dune 7or b>*an7  ab\t #fj  
to #ge met]s high 7photograph by ,?omas 
,s4 ,ahlbr&t74    ,data on anci5t s&    
seas 7va/ regions ( s& dunes71 *ang+    
lake  bas9s1 ar*aeology1 & vegetation   
analyses indicate t climatic  conditions
 h *ang$ consid]ably ov] va/ areas ( !  
,e>? 9 !  rec5t geologic pa/4 ,dur+ !   

la/ #ab1ejj ye>s1 = example1 p>ts  ( !  
des]ts 7 m arid ?an !y are today4 ,ab\t 
#aj p]c5t (  ! l& betwe5 #cj ,n4 & #cj  
,s4 is cov]$ n[ by s& seas4 ,ne>ly      
#ah1jjj ye>s ago1 s& seas 9 two va/     
belts occupi$ almo/ #ej p]c5t  ( ?is l& 
area4 ,z is ! case today1 tropical ra9  
=e/s &  savannahs 7 betwe5 ! two belts4 
,illu/ration3 ,a dry community (        
vegetation gr[s among ! dunes (  !      
,nebraska ,s& ,hills 7photograph by ,n4 
,h4 ,d>ton74    ,fossil des]t s$im5ts t 
are z mu* z #ejj million ye>s old h  be5
 f\nd 9 _m p>ts ( ! _w4 ,s& dune-l      
patt]ns h be5  recogniz$ 9 pres5tly     
non>id environm5ts4 ,_m su* relict dunes
 n[  receive f #hj to #aej millimet]s ( 
ra9 ea* ye>4 ,"s anci5t dunes  are 9    
areas n[ occupi$ by tropical ra9 =e/s4  
,! ,nebraska ,s& ,hills is an inactive  
#eg1jjj-squ>e kilomet] dune  field 9    
c5tral ,nebraska4 ,! l>ge/ s& sea 9 !   
,we/]n  ,hemisph]e1 x is n[ /abiliz$ by 
vegetation & receives ab\t #ejj         
millimet]s ( ra9 ea* ye>4 ,dunes 9 ! ,s&

 ,hills are up to #abj  met]s high4     
,extrat]re/rial des]ts    ,m>s is ! only
 o!r planet on :i* we h id5tifi$        
w9d-%ap$  7eolian7 features4 ,al?\gh its
 surface atmosph]ic pressure is only    
ab\t "o-hundr$? t ( ,e>?1 global        
circulation patt]ns on ,m>s  h =m$ a    
circumpol> s& sea ( m ?an five million  
squ>e  kilomet]s1 an area great] ?an !  
,empty ,qu>t] ( ,saudi ,arabia1 !  l>ge/
 s& sea on our planet4 ,m>tian s& seas  
consi/ pr$om9antly  ( cresc5t-%ap$ dunes
 on pla9s ne> ! p]5nial ice cap ( !     
nor? pol> area4 ,small] dune fields     
occupy ! floors ( _m l>ge  crat]s 9 !   
pol> regions4    ,illu/ration3 ,?is     
,vik+ spacecraft image ( ,m>s %[s       
alt]nat+  lay]s ( ice & w9dbl[n du/ ne> 
! nor? pol> cap4 ,annual &  o!r p]iodic 
climatic *anges due to orbit            
fluctuations may occur on  ,m>s 7c\rtesy
 ( ,,usgs ,image ,process+ ,facility1   
,flag/aff1 ,arizona74    ,illu/ration3  
,"o ( ! fir/ images tak5 at ! ,vik+ #b  
l&+  site on ,m>s %[s ! p9k sky ov]     

,utopia & ! des]t pavem5t on  ! gr\nd   
7c\rtesy ( ,,nasa74    ,illu/ration3 ,"s
 ( ! cresc5t-%ap$ dunes 9 ?is ,vik+     
image (  ,m>s are m ?an a kilomet] wide4
 ,! d>k mat]ial t /reaks f  ! horn-%ap$ 
features may be du/ rec5tly bl[n f !    
dunes  7c\rtesy ( ,,nasa74              
,illu/ration3 ,natural ,bridge1 ,ar*es  
,national ,monum5t1 ,utah  7photograph  
by ,pet] ,kresan74                      
,des]t ,features      ,s& cov]s only    
ab\t #bj p]c5t ( ! ,e>?'s des]ts4 ,mo/ (
 !  s& is 9 s& %eets & s& seas--va/     
regions ( undulat+ dunes  resembl+ ocean
 waves 8froz50 9 an in/ant ( "t4        
,ne>ly #ej p]c5t ( des]t surfaces are   
pla9s :]e eolian  deflation--removal (  
f9e-gra9$ mat]ial by ! w9d--has expos$  
loose  gravels consi/+ pr$om9antly (    
pebbles b ) occasional cobbles4    ,!   
rema9+ surfaces ( arid l&s are compos$ (
 expos$ b$rock  outcrops1 des]t soils1 &
 fluvial deposits includ+ alluvial fans1
  playas1 des]t lakes1 & oases4 ,b$rock 
outcrops commonly occur z  small m\nta9s

 surr\nd$ by ext5sive erosional pla9s4  
,oases are vegetat$ areas moi/5$ by     
spr+s1 wells1 or by irrigation4  ,_m are
 artificial4 ,oases are (t5 ! only      
places 9 des]ts t  support crops &      
p]man5t habitation4    ,illu/ration3    
,und]gr\nd *annels c>ry wat] f ne>by    
m\nta9s  into ! ,turpan ,depression (   
,*9a4 ,if ! *annels 7 n cov]$1  ! wat]  
w\ld evaporate quickly :5 x rea*$ ! hot1
 dry des]t  l&4                         
,soils    ,soils t =m 9 arid climates   
are pr$om9antly m9]al soils )  l[       
organic cont5t4 ,! repeat$ accumulation 
( wat] 9 "s soils  causes di/9ct salt   
lay]s to =m4 ,calcium c>bonate          
precipitat$ f  solution may cem5t s& &  
gravel into h>d lay]s call$ 8calcrete0  
t =m lay]s up to #ej met]s ?ick4        
,cali*e is a r$di%-br[n to :ite lay]    
f\nd 9 _m des]t soils4  ,cali*e commonly
 occurs z nodules or z coat+s on m9]al  
gra9s  =m$ by ! complicat$ int]action   
betwe5 wat] & c>bon dioxide  releas$ by 
plant roots or by decay+ organic        

mat]ial4                                
,plants    ,mo/ des]t plants are dr\ght-
 or salt-tol]ant4 ,"s /ore wat] 9  _!   
leaves1 roots1 & /ems4 ,o!r des]t plants
 h long tap roots  t p5etrate ! wat]    
table1 an*or ! soil1 & control erosion4 
,! /ems & leaves ( "s plants l[] !      
surface velocity (  s&-c>ry+ w9ds &     
protect ! gr\nd f erosion4              
,illu/ration3 ,sp>se1 v dry1 s+le       
species vegetation 9 ,dea?  ,valley1    
,cali=nia4    ,illu/ration3 ,vegetation 
amid/ ! des]t pavem5t ( ! ,sonoran      
,des]t 7photograph by ,john ,ols574     
,des]ts typically h a plant cov] t is   
sp>se b enorm\sly  div]se4 ,! ,sonoran  
,des]t ( ! ,am]ican ,s\?we/ has ! mo/   
complex des]t vegetation on ,e>?4 ,!    
giant sagu>o cacti provide  ne/s = des]t
 birds & s]ve z 8trees0 ( ! des]t4      
,sagu>o gr[  sl[ly b may live #bjj ye>s4
 ,:5 #i ye>s old1 !y are ab\t #ae       
c5timet]s high4 ,aft] ab\t #ge ye>s1 !  
cacti are tall & develop  _! fir/       
bran*es4 ,:5 fully gr[n1 sagu>o are #ae 

met]s tall &  weigh z mu* z #aj tons4   
,!y dot ! ,sonoran & re9=ce ! g5]al     
impression ( des]ts z cacti-ri* l&4     
,al?\gh cacti are (t5 ?\ght ( z         
*>act]i/ic des]t plants1  o!r types (   
plants h adapt$ well to ! arid          
environm5t4 ,!y  include ! pea family & 
sunfl[] family4 ,cold des]ts h grasses  
& %rubs z dom9ant vegetation4           
,wat]    ,ra9 does fall occasionally 9  
des]ts1 & des]t /orms are (t5  viol5t4  
,a record #dd millimet]s ( ra9 once fell
 )9 #c h\rs 9 !  ,sah>a4 ,l>ge ,sah>an  
/orms may deliv] up to #a millimet] p]  
m9ute4  ,normally dry /ream *annels1    
call$ arroyos or wadis1 c quickly fill  
aft] heavy ra9s1 & fla% floods make ^!  
*annels dang]\s4 ,m  p dr[n 9 des]ts ?an
 die ( ?ir/4    ,?\gh little ra9 falls 9
 des]ts1 des]ts receive run(f f         
ephem]al1 or %ort-liv$1 /reams f$ by ra9
 & sn[ f adjac5t  highl&s4 ,^! /reams   
fill ! *annel ) a slurry ( mud &        
commonly transport consid]able          
quantities ( s$im5t = a day or two4     

,al?\gh mo/ des]ts are 9 bas9s ) clos$1 
or int]ior dra9age1 a  few des]ts are   
cross$ by #8exotic' riv]s t d]ive _!    
wat] f  outside ! des]t4 ,su* riv]s     
infiltrate soils & evaporate l>ge       
am\nts ( wat] on _! j\rneys ?r\gh !     
des]ts1 b _!  volumes are su* t !y      
ma9ta9 _! cont9uity4 ,! ,nile1 !        
,colorado1 & ! ,yell[ are exotic riv]s t
 fl[ ?r\gh des]ts to  deliv] _! s$im5ts 
to ! sea4    ,illu/ration3 ,! ,wei ,riv]
 9 ! ,loess ,plateau1 ,*9a 7photograph  
by  ,i-,m+ ,*\74    ,illu/ration3 ,runn+
 wat] creat$ ?is canyon 9 arid ,big ,b5d
  ,national ,p>k1 s\?we/ ,texas4        
,lakes =m :]e ra9fall or meltwat] 9     
int]ior dra9age bas9s is  suffici5t4    
,des]t lakes are g5]ally %all[1         
tempor>y1 & salty4  ,because ^! lakes   
are %all[ & h a l[ bottom gradi5t1 w9d  
/ress may cause ! lake wat]s to move ov]
 _m squ>e kilomet]s4  ,:5 small lakes   
dry up1 !y leave a salt cru/ or h>dpan4 
,! flat  area ( clay1 silt1 or s&       
encru/$ ) salt t =ms is kn[n z a  playa4

 ,!re are m ?an a hundr$ playas 9 ,nor? 
,am]ican des]ts4  ,mo/ are relics ( l>ge
 lakes t exi/$ dur+ ! la/ ,ice ,age     
ab\t #ab1jjj ye>s ago4 ,lake ,bonneville
 0 a #eb1jjj-squ>e-kilomet]  lake almo/ 
#cjj met]s deep 9 ,utah1 ,nevada1 &     
,idaho dur+ ! ,ice  ,age4 ,today !      
remnants ( ,lake ,bonneville include    
,utah's ,great ,salt  ,lake1 ,utah      
,lake1 & ,sevi] ,lake4 ,because playas  
are arid l& =ms  f a wett] pa/1 !y      
conta9 useful clues to climatic *ange4  
,! flat t]ra9s ( h>dpans & playas make  
!m excell5t race tracks  & natural      
runways = airplanes & spacecraft4       
,gr\nd-vehicle spe$  records are        
commonly e/abli%$ on ,bonneville        
,spe$way1 a race track on  ! ,great     
,salt ,lake h>dpan4 ,space %uttles l& on
 ,rog]s ,lake ,playa at  ,edw>ds ,air   
,=ce ,base1 ,cali=nia4    ,illu/ration3 
,! ,qaidam ,depression 9 ,*9a is !      
highe/ des]t 9  ! _w4 ,?is ,l&sat image 
illu/rates a salt lake & evaporite      
bas9s 9 ! depression4                   

,eolian ,processes      ,eolian         
processes p]ta9 to ! activity ( ! w9ds4 
,w9ds may erode1  transport1 & deposit  
mat]ials1 & are effective ag5ts 9       
regions  ) sp>se vegetation & a l>ge    
supply ( unconsolidat$ s$im5ts4  ,al?\gh
 wat] is mu* m p[]ful ?an w9d1 eolian   
processes are  important 9 arid         
environm5ts4                            
,eolian erosion    ,w9d erodes ! ,e>?'s 
surface by deflation1 ! removal ( loose1
  f9e-gra9$ p>ticles by ! turbul5t eddy 
action ( ! w9d1 & by  abrasion1 ! we>+  
d[n ( surfaces by ! gr9d+ action & s&   
bla/+ ( w9dborne p>ticles4    ,mo/      
eolian deflation zones are compos$ (    
des]t pavem5t1 a  %eetlike surface (    
rock fragm5ts t rema9s aft] w9d & wat]  
h remov$ ! f9e p>ticles4 ,almo/ half ( !
 ,e>?'s des]t  surfaces are /ony        
deflation zones4 ,! rock mantle 9 des]t 
pavem5ts  protects ! und]ly+ mat]ial f  
deflation4    ,illu/ration3 ,! s& & rock
 ( ,*9a's ,turpan ,depression resemble  
closely ^? 9 ! view ( ! ,m>tian surface 

on page #ba4    ,illu/ration3 ,! arr[   
po9ts to %9y black des]t v>ni% on ^!    
rocks ( ,egypt's s\?we/ des]t           
7photograph by ,c>ol ,bre$74    ,a d>k1 
%9y /a91 call$ des]t v>ni% or rock      
v>ni%1 is (t5  f\nd on surfaces ( "s    
des]t rocks t h be5 expos$ at !  surface
 = a long p]iod ( "t4 ,manganese1 iron  
oxides1 hydroxides1  & clay m9]als =m   
mo/ v>ni%es & provide ! %9e4            
,deflation bas9s1 call$ bl[\ts1 are     
holl[s =m$ by ! removal  ( p>ticles by  
w9d4 ,bl[\ts are g5]ally small1 b may be
 up to  sev]al kilomet]s 9 diamet]4     
,w9d-driv5 gra9s abrade l&=ms4 ,gr9d+ by
 p>ticles c>ri$ 9  ! w9d creates grooves
 or small depressions4 ,v5tifacts are   
rocks  :i* h be5 cut1 & sometimes       
poli%$1 by ! abrasive action (  w9d4    
,sculpt$ l&=ms1 call$ y>dangs1 are up to
 t5s ( met]s high &  kilomet]s long &   
are =ms t h be5 /reaml9$ by des]t  w9ds4
 ,! fam\s sph9x at ,giza 9 ,egypt may be
 a modifi$ y>dang4        ,y>dangs ( !  
,lut ,des]t ( ,iran4 ,^! y>dangs are    

among !            l>ge/ on ,e>?1 )     
almo/ #ajj met]s ( relief4              
,illu/ration3 ,view f ,l&sat4           
,illu/ration3 ,view f high-altitude     
photograph 7photograph by ,u4,s4  ,air  
,=ce74    ,illu/ration3 ,view f         
l[-altitude photograph 7photograph by   
,j4,t4  ,daniels74                      
,eolian transportation    ,p>ticles are 
transport$ by w9ds ?r\gh susp5sion1     
saltation1 &  creep4    ,small p>ticles 
may be held 9 ! atmosph]e 9 susp5sion4  
,upw>d  curr5ts ( air support ! weight (
 susp5d$ p>ticles & hold !m  indef9itely
 9 ! surr\nd+ air4 ,typical w9ds ne> !  
,e>?'s  surface susp5d p>ticles less ?an
 #j4b millimet]s 9 diamet] &  scatt] !m 
al(t z du/ or haze4    ,saltation is    
d[nw9d movem5t ( p>ticles 9 a s]ies (   
jumps or  skips4 ,saltation normally    
lifts s&-size p>ticles no m ?an "o      
c5timet] above ! gr\nd1 & proce$s at    
"o-half to "o-?ird !  spe$ ( ! w9d4 ,a  
saltat+ gra9 may hit o!r gra9s t jump up
  to cont9ue ! saltation4 ,! gra9 may   

also hit l>g] gra9s t are  too heavy to 
hop1 b t sl[ly creep =w>d z !y are pu%$ 
by  saltat+ gra9s4 ,surface creep       
acc\nts = z mu* z #be p]c5t (  gra9     
movem5t 9 a des]t4    ,eolian turbidity 
curr5ts are bett] kn[n z du/ /orms4 ,air
 ov]  des]ts is cool$ significantly :5  
ra9 passes ?r\gh x4 ,?is cool]  & d5s]  
air s9ks t[>d ! des]t surface4 ,:5 x    
rea*es !  gr\nd1 ! air is deflect$ =w>d 
& sweeps up surface debris 9 its        
turbul5ce z a du/ /orm4    ,illu/ration3
 ,saltation moves small p>ticles 9 !    
direction ( !  w9d 9 a s]ies ( %ort hops
 or skips4    ,crops1 p1 villages1 &    
possibly ev5 climates are affect$ by du/
  /orms4 ,"s du/ /orms are              
int]cont95tal1 a few may circle !       
globe1 & occasionally !y may engulf     
entire planets4 ,:5 ! ,m>9]  #i         
spacecraft arriv$ at ,m>s 9 #aiga1 !    
entire planet 0 en%r\d$  9 global du/4  
,illu/ration3 ,du/ /orm along ! ,mohave 
,riv] ne> ,daggett1  ,cali=nia1 ,octob] 
#bd1 #aiai 7photograph by ,d4 ,g4       

,?ompson74    ,mo/ ( ! du/ c>ri$ by du/ 
/orms is 9 ! =m ( silt-size  p>ticles4  
,deposits ( ?is w9dbl[n silt are kn[n z 
loess4 ,!  ?icke/ kn[n deposit ( loess1 
#cce met]s1 is on ! ,loess ,plateau 9   
,*9a4 ,9 ,europe & 9 ! ,am]icas1        
accumulations ( loess are  g5]ally f #bj
 to #cj met]s ?ick4    ,small :irlw9ds1 
call$ du/ devils1 are common 9 arid l&s 
& are  ?\ght to be relat$ to v int5se   
local heat+ ( ! air t  results 9        
in/abilities ( ! air mass4 ,du/ devils  
may be z mu* z  "o kilomet] high4       
,eolian deposition    ,w9d-deposit$     
mat]ials hold clues to pa/ z well z to  
pres5t w9d  directions & int5sities4 ,^!
 features help u und]/& !  pres5t       
climate & ! =ces t mold$ x4             
,w9d-deposit$ s&  bodies occur z s&     
%eets1 ripples1 & dunes4    ,s& %eets   
are flat1 g5tly undulat+ s&y plots ( s& 
surfac$  by gra9s t may be too l>ge =   
saltation4 ,!y =m approximately  #dj    
p]c5t ( eolian depositional surfaces4 ,!
 ,selima ,s& ,%eet1 :i*  occupies       

#fj1jjj squ>e kilomet]s 9 s\!rn ,egypt &
 nor!rn ,sudan1  is "o ( ! ,e>?'s l>ge/ 
s& %eets4 ,! ,selima is absolutely flat 
9 "s places2 9 o!rs1 active dunes move  
ov] its surface4    ,w9d bl[+ on a s&   
surface ripples ! surface into cre/s &  
tr\ghs ^: long axes are p]p5dicul> to ! 
w9d direction4 ,!  av]age l5g? ( jumps  
dur+ saltation corresponds to !         
wavel5g?1  or di/ance betwe5 adjac5t    
cre/s1 ( ! ripples4 ,9 ripples1 !       
co>se/ mat]ials collect at ! cre/s4 ,?is
 di/+ui%es small  ripples f dunes1 :]e !
 co>se/ mat]ials are g5]ally 9 !        
tr\ghs4    ,illu/ration3 ,w9d-bl[n s&   
moves up ! g5tle upw9d side ( !  dune by
 saltation or creep4 ,s& accumulates at 
! br9k1 ! top (  ! slipface4 ,:5 !      
buildup ( s& at ! br9k exce$s ! angle ( 
repose1 a small avalan*e ( gra9s slides 
d[n ! slipface4 ,gra9 by  gra91 ! dune  
moves d[nw9d4    ,accumulations ( s$im5t
 bl[n by ! w9d into a m\nd or ridge1    
dunes  h g5tle upw9d slopes on !        
w9d-fac+ side4 ,! d[nw9d portion  ( !   

dune1 ! lee slope1 is commonly a /eep   
avalan*e slope ref]r$  to z a slipface4 
,dunes may h m ?an "o slipface4 ,!      
m9imum  height ( a slipface is ab\t #cj 
c5timet]s4    ,s& gra9s move up ! dune's
 g5tle upw9d slope by saltation &       
creep4 ,:5 p>ticles at ! br9k ( ! dune  
exce$ ! angle (  repose1 !y spill ov] 9 
a t9y l&slide or avalan*e t re=ms  !    
slipface4 ,z ! avalan*+ cont9ues1 ! dune
 moves 9 !  direction ( ! w9d4    ,"s ( 
! mo/ significant exp]im5tal measurem5ts
 on eolian s&  movem5t 7 p]=m$ by ,ralph
 ,bagnold1 a ,briti% eng9e] :o work$  9 
,egypt prior to ,_w ,w> ,,ii4 ,bagnold  
inve/igat$ ! physics (  p>ticles mov+   
?r\gh ! atmosph]e & deposit$ by w9d4 ,he
  recogniz$ two basic dune types1 !     
cresc5tic dune1 :i* he call$  8b>*an10 &
 ! l9e> dune1 :i* he call$ longitud9al  
or 8sief0  7,arabic = 8sword074         
,illu/ration3 ,s& dunes 9 ,dea? ,valley1
 ,cali=nia 7photograph by  ,ri*>d       
,fre>74    ,illu/ration3 ,ripples on a  
dune 9 ,eureka ,valley1 ,cali=nia       

7photograph by ,t]r5ce ,moore74         
,types ( ,dunes      ,a worldwide       
inv5tory ( des]ts has be5 develop$ us+  
images f  ! ,l&sat satellites & f space 
& a]ial photography4 ,x def9es  five    
basic types ( dunes3 cresc5tic1 l9e>1   
/>1 dome1 &  p>abolic4    ,illu/ration3 
,^! cresc5tic dunes ( coa/al ,p]u are   
migrat+  t[>d ! left 7photograph by     
,john ,mc,cauley74    ,! mo/ common dune
 =m on ,e>? & on ,m>s is ! cresc5tic4   
,cresc5t-%ap$ m\nds g5]ally are wid] ?an
 long4 ,! slipface is on  ! dune's      
concave side4 ,^! dunes =m "u w9ds t bl[
 f "o  direction1 & !y also are kn[n z  
b>*ans1 or transv]se dunes4  ,"s types (
 cresc5tic dunes move fa/] ov] des]t    
surfaces ?an any  o!r type ( dune4 ,a   
gr\p ( dunes mov$ m ?an #ajj met]s p]   
ye>  betwe5 #aied & #aiei 9 ,*9a's      
,n+xia ,prov9ce2 simil> rates h  be5    
record$ 9 ! ,we/]n ,des]t ( ,egypt4 ,!  
l>ge/ cresc5tic  dunes on ,e>?1 ) mean  
cre/-to-cre/ wid?s ( m ?an #c           
kilomet]s1 are 9 ,*9a's ,taklimakan     

,des]t4    ,/raight or slightly s9u\s s&
 ridges typically mu* long] ?an !y  are 
wide are kn[n z l9e> dunes4 ,!y may be m
 ?an #afj  kilomet]s long4 ,l9e> dunes  
may occur z isolat$ ridges1 b !y        
g5]ally =m sets ( p>allel ridges sep>at$
 by miles ( s&1  gravel1 or rocky       
int]dune corridors4 ,"s l9e> dunes m]ge 
to =m  ,y-%ap$ comp\nd dunes4 ,_m =m 9  
bidirectional w9d regimes4 ,!  long axes
 ( ^! dunes ext5d 9 ! resultant         
direction ( s&  movem5t4                
,illu/ration3 ,/> dunes1 su* z ^! ( !   
,namib1 indicate !  w9ds t =m$ !m blew f
 _m directions 7photograph by ,georg    
,g]/]74    ,radially symmetrical1 />    
dunes are pyramidal s& m\nds )          
slipfaces on ?ree or m arms t radiate f 
! high c5t] ( !  m\nd4 ,!y t5d to       
accumulate 9 areas ) multidirectional   
w9d  regimes4 ,/> dunes gr[ upw>d r ?an 
lat]ally4 ,!y dom9ate !  ,gr& ,erg      
,ori5tal ( ! ,sah>a4 ,9 o!r des]ts1 !y  
occur ar\nd  ! m>g9s ( ! s& seas1       
p>ticul>ly ne> topographic b>ri]s4 ,9  !

 s\!a/ ,bada9 ,j>an ,des]t ( ,*9a1 ! /> 
dunes are up to #ejj  met]s tall & may  
be ! talle/ dunes on ,e>?4              
,illu/ration3 ,l9e> dunes advance on    
small playas ea/ ( ,lake ,eyre 9  !     
,simpson ,des]t ( c5tral ,au/ralia      
7photograph by ,c4 ,twidale74           
,illu/ration3 ,l9e> dunes 9 ! ,we/]n    
,des]t ( ,egypt 7photograph  by ,c>ol   
,bre$74    ,oval or circul> m\nds t     
g5]ally lack a slipface1 dome dunes are 
r>e & occur at ! f> upw9d m>g9s ( s&    
seas4    ,u-%ap$ m\nds ( s& ) convex    
noses trail$ by elongat$ arms are       
p>abolic dunes4 ,sometimes ^! dunes are 
call$ ,u-%ap$1 bl[\t1  or hairp9 dunes1 
& !y are well kn[n 9 coa/al des]ts4     
,unlike  cresc5tic dunes1 _! cre/s po9t 
upw9d4 ,! elongat$ arms (  p>abolic     
dunes foll[ r ?an lead because !y h be5 
fix$ by  vegetation1 :ile ! bulk ( ! s& 
9 ! dune migrates =w>d4 ,!  longe/ kn[n 
p>abolic dune has a trail+ arm #ab      
kilomet]s long4    ,illu/ration3 ,small 
cresc5tic dunes occur on ! cre/s ( ^!   

complex dome dunes ( ,saudi ,arabia's   
,empty ,qu>t] 7photograph by ,elwood    
,fries574    ,illu/ration3 ,ripples &   
horns ( ?is cresc5tic dune 9 ,egypt     
indicate t ! dune is mov+ "r to left    
7photograph by ,john  ,ols574           
,occurr+ :]ev] w9ds p]iodically rev]se  
direction1 rev]s+  dunes are v>ieties ( 
any ( ! above types4 ,^! dunes typically
  h major & m9or slipfaces ori5t$ 9     
opposite directions4    ,all ^! dune    
types may occur 9 ?ree =ms3 simple1     
comp\nd1 &  complex4 ,simple dunes are  
basic =ms ) a m9imum numb] (  slipfaces 
t def9e ! geometric type4 ,comp\nd dunes
 are l>ge dunes  on :i* small] dunes (  
simil> type & slipface ori5tation are   
sup]impos$1 & complex dunes are         
comb9ations ( two or m dune  types4 ,a  
cresc5tic dune ) a /> dune sup]impos$ on
 its cre/ is  ! mo/ common complex dune4
 ,simple dunes repres5t a w9d regime t  
has n *ang$ 9 int5sity or direction s9ce
 ! =mation ( !  dune1 :ile comp\nd &    
complex dunes sugge/ t ! int5sity &     

direction ( ! w9d has *ang$4            
,illu/ration3 ,! nor!rn ,mojave ,des]t4 
,! ,l&sat ,!matic ,mapp]  7,,tm7        
acquires data 9 sev5 b&s ( !            
electromagnetic spectrum4 ,on  ?is      
image1 :ite & yell[ colors indicate     
rocks ri* 9 clay m9]als  & limonite 9   
rocks ( r$ & yell[ hues4 ,! l>ge        
conc5trations  ( limonite & clays may   
indicate m9]al deposits expos$ at !     
surface or buri$ up to sev]al ?\s& feet 
bel[ x 7photograph  c\rtesy ( ,melv9    
,podwysocki74                           
,remote ,s5s+ ( ,arid ,l&s      ,! _w's 
des]ts are g5]ally remote1 inaccessible1
 &  inhospitable4 ,hidd5 among !m1      
h[ev]1 are hydroc>bon res]voirs1        
evaporites1 & o!r m9]al deposits1 z well
 z human artifacts  pres]v$ = c5turies  
by ! arid climate4 ,9 ^! h>%            
environm5ts1 ! in=mation & p]spective   
requir$ to increase our  und]/&+ (      
arid-l& geology & res\rces (t5 dep5ds on
  remote-s5s+ me?ods4 ,remote s5s+ is ! 
collection ( in=mation  ab\t an object  

)\t be+ 9 direct physical contact ) x4  
,remote-s5s+ in/rum5ts 9 ,e>?-orbit     
satellites measure rad>1  visible light1
 & infr>$ radiation4 ,rad> imag+ sy/ems 
provide  _! own s\rce ( electromagnetic 
en]gy1 s !y c op]ate at any  "t ( day or
 night4 ,additionally1 cl\ds & all b !  
mo/ sev]e  /orms are transp>5t to rad>4 
,! fir/ ,%uttle ,imag+ ,rad> ,sy/em     
7,,sir-,a71 fl[n on ! ,u4,s4 space      
%uttle ,columbia 9 #aiha1 record$ images
 t %[ buri$ fluvial  topography1 faults1
 & intrusive bodies o!rwise conceal$    
b5ea?  s& %eets & dunes ( ! ,we/]n      
,des]t 9 ,egypt & ! ,sudan4 ,mo/  ( ^!  
features are n visible f ! gr\nd4 ,!    
rad> signal  p5etrat$ loose dry s&s &   
return$ images ( buri$ riv] *annels  n  
visible at ! surface4 ,^! images help$  
f9d new ar*eologic  sites & s\rces (    
potable wat] 9 ! des]t4 ,^! 8rad> riv]s0
  are ! remnants ( a n[ vani%$ major    
riv] sy/em t fl[$ across  ,africa "s #bj
 million ye>s be=e ! developm5t ( !     
,nile ,riv]  sy/em4 ,rad> imag]y also is

 a p[]ful tool = explor+ = plac]  m9]al 
deposits 9 arid l&s4    ,9 #aigb1 !     
,unit$ ,/ates laun*$ ! fir/ ( a gr\p (  
unmann$  satellites collectively kn[n z 
,l&sat4 ,l&sat satellites c>ry  s5sors t
 record 8light10 or portions ( !        
electromagnetic  spectrum1 z x reflects 
(f ! ,e>?4 ,l&sat acquires digital data 
t are conv]t$ into an image4            
,illu/ration3 ,! ,l&sat simulat$ true   
color mosaic 7left7 %[s !  ,selima ,s&  
,%eet cov]+ all b rocky areas ( ! ,sah>a
 ,des]t 9  ,sudan4 ,on ! "r1 a          
#ej-kilomet]-wide /rip ( ,%uttle ,imag+ 
,rad>1  ,,sir-,a1 is plac$ ov] ! ,l&sat 
mosaic to reveal old /ream *annels  &   
geologic /ructures l ^!4 ,/ructures t   
are o!rwise  invisible "u ! surface s&s 
are pot5tial s\rces ( wat]1 plac]       
m9]als1 anci5t artifacts1 & in=mation on
 *anges ( climate 9  arid areas 7c\rtesy
 ( ,,usgs ,image ,process+ ,facility1   
,flag/aff74    ,! sc>city ( vegetation  
makes spectral remote s5s+ especially   
effective 9 arid l&s4 ,rocks conta9+    

limonite1 a hydr\s iron  oxide1 may be  
id5tifi$ readily f ,l&sat ,multispectral
 ,scann]  data4 ,! ,l&sat ,!matic ,mapp]
 7,,tm7 has increas$ our ability to     
detect & map ! di/ribution ( m9]als 9   
volcanic rocks &  relat$ m9]al deposits 
9 arid & semi>id l&s4    ,m ?an a       
million images ( ,e>? h be5 acquir$ by !
 ,l&sat  satellites4 ,a ,l&sat image may
 be view$ z a s+le b& 9  black-&-:ite1  
or z a comb9ation repres5t$ by ?ree     
colors1 call$  a color composite4 ,! mo/
 widely us$ ,l&sat color image is call$ 
a  false-color composite because x      
reproduces ! infr>$ b& 7invisible  to ! 
nak$ eye7 z r$1 ! r$ b& z gre51 & ! gre5
 b& z  blue4 ,heal?y vegetation 9 a     
false-color composite is r$4    ,des]t  
/udies /ill are hamp]$ 9 _m regions by  
lack ( accurate  climate data4 ,mo/     
des]t wea!r /ations are 9 oases surr\nd$
 by  trees & build+s & h be5 subject$ to
 _m location &  elevation *anges ?r\gh\t
 ! life ( ! /ation4 ,data f oases d  n  
reflect conditions f ! surr\nd+ des]t4  

,a wide v>iety (  in/rum5ts has be5 us$ 
to record measurem5ts ov] v>y+ l5g?s (  
"t & 9 diff]5t =mats1 mak+ data         
difficult to int]pret &  comp>e4    ,to 
ov]come "s ( ^! problems 9 des]ts ( !   
,am]ican ,s\?we/1  ! ,u4,s4 ,geological 
,survey 7,,usgs7 e/abli%$ its ,des]t    
,w9ds ,project  to measure 9 a /&>d =mat
 sev]al key meteorologic *>act]i/ics  ( 
arid l&s4 ,project sci5ti/s h           
successfully e/abli%$  in/rum5t /ations 
to measure w9d-spe$1 includ+ peak gu/s1 
:i*  alt] ! l&=ms ! mo/4 ,a /ation      
record$ a w9d/orm ne>  ,vicksburg1      
,arizona1 = example1 ) peak gu/s ( almo/
 #aej  kilomet]s p] h\r4 ,us+           
l[-ma9t5ance1 automatic1 sol>-p[]$      
s5sors1 ! /ations also measure w9d      
direction1 precipitation1  humidity1    
soil & air temp]atures1 & b>ometric     
pressure at specific  heights above !   
surface4 ,data are sampl$ at #f-m9ute   
int]vals &  transmitt$ e #cj m9utes to a
 ,geo/ation>y ,op]ational  ,environm5tal
 ,satellite 7,,goes74 ,f ,,goes1 ! data 

are transmitt$ to  ! ,,usgs laboratory 9
 ,flag/aff1 ,arizona4    ,! ,des]t ,w9ds
 ,project's inve/igators comb9e analyses
 ( data )  detail$ geologic field /udies
 & repetitive remote-s5s+ cov]age  9    
ord] to inve/igate & und]/& ! long-t]m  
*anges produc$ by  w9d 9 des]ts ( diff]+
 geologic & climatic types4             
,illu/ration3 ,?is geometeorologic      
/ation ( ! ,des]t ,w9ds ,project        
measures w9d spe$ & direction1 soil &   
air temp]ature1 &  precipitation &      
humidity 9 ! ,great ,bas9 ,des]t        
7photograph by  ,c>ol ,bre$74           
,illu/ration3 ,nitrate work+s 9 a broad 
valley 9 ! ,atacama ,des]t  ( nor!rn    
,*ile1 :]e sal9e-cem5t$ surficial       
deposits =m$ ne>  a playa lake          
7photograph by ,george ,ericks574       
,m9]al ,res\rces 9 ,des]ts      ,"s     
m9]al deposits are =m$1 improv$1 or     
pres]v$ by geologic  processes t occur 9
 arid l&s z a consequ5ce ( climate4     
,gr\nd  wat] lea*es ore m9]als &        
r$eposits !m 9 zones ne> ! wat]  table4 

,?is lea*+ process conc5trates ^! m9]als
 z ore t c  be m9$4 ,( ! #ae major types
 ( m9]al deposits 9 ! ,we/]n  ,hemisph]e
 =m$ by action ( gr\nd wat]1 #ac occur 9
 des]ts4    ,evaporation 9 arid l&s     
enri*es m9]al accumulation 9 _! lakes4  
,playas may be s\rces ( m9]al deposits  
=m$ by evaporation4 ,wat]  evaporat+ 9  
clos$ bas9s precipitates m9]als su* z   
gypsum1 salts  7includ+ sodium nitrate &
 sodium *loride71 & borates4 ,!  m9]als 
=m$ 9 ^! evaporite deposits dep5d on !  
composition  & temp]ature ( ! sal9e     
wat]s at ! "t ( deposition4             
,significant evaporite res\rces occur 9 
! ,great ,bas9 ,des]t ( !  ,unit$       
,/ates1 m9]al deposits made =ev] fam\s  
by ! 8#bj-mule  teams0 t once haul$     
borax-lad5 wagons f ,dea? ,valley to !  
railroad4 ,boron1 f borax & borate      
evaporites1 is an ess5tial  +r$i5t 9 !  
manufacture ( glass1 c]amics1 enamel1   
agricultural  *emicals1 wat] s(t5]s1 &  
ph>maceuticals4 ,borates are m9$ f      
evaporite deposits at ,se>les ,lake1    

,cali=nia1 & o!r des]t  locations4 ,!   
total value ( *emicals t h be5 produc$ f
  ,se>les ,lake sub/antially exce$s #a  
billion4    ,! ,atacama ,des]t ( ,s\?   
,am]ica is unique among ! des]ts ( !  _w
 9 its great abundance ( sal9e m9]als4  
,sodium nitrate has be5  m9$ =          
explosives & f]tiliz] 9 ! ,atacama s9ce 
! middle (  ! #ai? c5tury4 ,ne>ly #c    
million metric tons 7 m9$ dur+ ,_w  ,w> 
,i4    ,valuable m9]als locat$ 9 arid   
l&s include copp] 9 ! ,unit$  ,/ates1   
,*ile1 ,p]u1 & ,iran2 iron & lead-z9c   
ore 9 ,au/ralia2  *romite 9 ,turkey2 &  
gold1 silv]1 & uranium deposits 9       
,au/ralia  & ! ,unit$ ,/ates4           
,nonmetallic m9]al res\rces & rocks su* 
z  b]yllium1 mica1 li?ium1 clays1       
pumice1 & scoria also occur 9 arid      
regions4 ,sodium c>bonate1 sulfate1     
borate1 nitrate1 li?ium1 brom9e1  iod9e1
 calcium1 & /rontium comp\nds come f    
s$im5ts &  ne>surface br9es =m$ by      
evaporation ( inl& bodies ( wat]1  (t5  
dur+ geologically rec5t times4          

,illu/ration3 ,?is op5-pit m9e 9 !      
,sonoran ,des]t ne> ,ajo1  ,arizona1 has
 expos$ an elliptical copp] deposit ab\t
 #a1jjj met]s  long & #gej met]s wide4  
,! copp] ore m9$ "h is 9 a b$ t  av]ages
 #aej met]s 9 ?ickness 7photograph by   
,pet] ,kresan74    ,! ,gre5 ,riv]       
,=mation ( ,colorado1 ,wyom+1 & ,utah   
conta9s  alluvial fan deposits & playa  
evaporites creat$ 9 a huge lake ^:      
level fluctuat$ = millions ( ye>s4      
,economically significant  deposits (   
trona1 a major s\rce ( sodium comp\nds1 
& ?ick lay]s  ( oil %ale 7 creat$ 9 !   
arid environm5t4    ,illu/ration3 ,trona
 m9e at ,se>les ,lake1 ,cali=nia        
7photograph by  ,john ,kei?74    ,"s ( !
 m productive petroleum areas on ,e>?   
are f\nd 9 arid  & semi>id regions (    
,africa & ! ,midea/1 al?\gh ! oil       
res]voirs 7 orig9ally =m$ 9 %all[ m>9e  
environm5ts4 ,rec5t  climate *ange has  
plac$ ^! res]voirs 9 an arid environm5t4
    ,o!r oil res]voirs1 h[ev]1 are      
presum$ to be eolian 9 orig9 &  are     

pres5tly f\nd 9 humid environm5ts4 ,!   
,rotlieg5des1 a  hydroc>bon res]voir 9 !
 ,nor? ,sea1 is associat$ ) ext5sive    
evaporite deposits4 ,_m ( ! major ,u4,s4
 hydroc>bon res\rces may  come f eolian 
s&s4 ,anci5t alluvial fan sequ5ces may  
also be  hydroc>bon res]voirs4          
,illu/ration3 ,! ,sahelian dr\ght t     
began 9 #aifh 0 responsible  = ! dea?s (
 betwe5 #ajj1jjj & #bej1jjj p1 !        
disruption (  millions ( lives1 & !     
collapse ( ! agricultural bases ( five  
c\ntries 7photograph by ,daniel ,/iles1 
,,unep74                                
,des]tification      ,! _w's great      
des]ts 7 =m$ by natural processes       
int]act+  ov] long int]vals ( "t4 ,dur+ 
mo/ ( ^! times1 des]ts h  gr[n & %runk  
indep5d5t ( human activities4           
,paleodes]ts1 l>ge  s& seas n[ inactive 
because !y are /abiliz$ by vegetation1  
ext5d  well beyond ! pres5t m>g9s ( core
 des]ts1 su* z ! ,sah>a4 ,9  "s regions1
 des]ts are sep>at$ %>ply f surr\nd+1   
less arid  areas by m\nta9s & o!r       

contra/+ l&=ms t reflect basic          
/ructural diff]5ces 9 ! regional        
geology4 ,9 o!r areas1 des]t  fr+es =m a
 gradual transition f a dry to a m humid
  environm5t1 mak+ x m difficult to     
def9e ! des]t bord]4    ,illu/ration3   
,ov]graz+ has made ! ,rio ,pu]co ,bas9 (
 c5tral ,new  ,mexico "o ( ! mo/ erod$  
riv] bas9s ( ! ,am]ican ,we/ & has      
increas$ ! high s$im5t cont5t ( ! riv]  
7photograph by ,t]r5ce  ,moore74        
,illu/ration3 ,l9e> dunes ( ! ,sah>a    
,des]t encroa* on ,n\ak*ott1  ! capital 
( ,mauritania4 ,! dunes bord] a mosque  
at left 7photograph  by ,georg ,g]/]74  
,^! transition zones h v fragile1       
delicately balanc$  ecosy/ems4 ,des]t   
fr+es (t5 are a mosaic ( microclimates4 
,small  holl[s support vegetation t     
picks up heat f ! hot w9ds &  protects !
 l& f ! prevail+ w9ds4 ,aft] ra9fall !  
vegetat$ areas are di/9ctly cool] ?an ! 
surr\nd+s4 ,9 ^!  m>g9al areas1 human   
activity may /ress ! ecosy/em beyond its
  tol]ance limit1 result+ 9 degradation 

( ! l&4 ,by p\nd+ !  soil ) _! hooves1  
live/ock compact ! sub/rate1 increase ! 
proportion ( f9e mat]ial1 & r$uce !     
p]colation rate ( !  soil1 ?us enc\rag+ 
erosion by w9d & wat]4 ,graz+ & !       
collection ( firewood r$uces or         
elim9ates plants t help to b9d  ! soil4 
,?is degradation ( =m]ly productive     
l&--des]tification--is a  complex       
process4 ,x involves multiple causes1 & 
x proce$s at v>y+  rates 9 diff]5t      
climates4 ,des]tification may int5sify a
 g5]al  climatic tr5d t[>d great]       
aridity1 or x may initiate a *ange 9    
local climate4    ,des]tification does n
 occur 9 l9e>1 easily mappable patt]ns4 
,des]ts advance erratically1 =m+ pat*es 
on _! bord]s4 ,areas f>  f natural      
des]ts c degrade quickly to b>r5 soil1  
rock1 or s&  ?r\gh poor l& managem5t4 ,!
 pres5ce ( a ne>by des]t has no  direct 
relation%ip to des]tification4          
,un=tunately1 an area  und]go+          
des]tification is br\ght to public      
att5tion only aft] !  process is well   

und]way4 ,(t5 little or no data are     
available to  indicate ! previ\s /ate ( 
! ecosy/em or ! rate ( degradation4     
,sci5ti/s /ill "q :e!r des]tification1 z
 a process (  global *ange1 is p]man5t  
or h[ & :5 x c be halt$ or  rev]s$4     
,illu/ration3 ,camels & o!r animals     
trample ! soil 9 ! semi>id  ,sahel (    
,africa z !y move to wat] holes su* z   
?is "o 9 ,*ad  7photograph c\rtesy ( !  
,u4,s4 ,ag5cy = ,int]national           
,developm5t74                           
,problem    ,des]tification became well 
kn[n 9 ! #aicj's1 :5 p>ts ( ! ,great    
,pla9s 9 ! ,unit$ ,/ates turn$ into !   
8,du/ ,b[l0 z a result (  dr\ght & poor 
practices 9 f>m+1 al?\gh ! t]m itself 0 
n  us$ until almo/ #aiej4 ,dur+ ! du/   
b[l p]iod1 millions ( p  7 =c$ to ab&on 
_! f>ms & livelihoods4 ,greatly improv$ 
me?ods ( agriculture & l& & wat]        
managem5t 9 ! ,great ,pla9s  h prev5t$ t
 disa/] f recurr+1 b des]tification     
pres5tly affects millions ( p 9 almo/ e 
cont95t4    ,illu/ration3 ,(f-road      

vehicles significantly increase soil    
loss 9 !  delicate des]t environm5t ( ! 
we/]n ,unit$ ,/ates4 ,9 a few  seconds1 
soils t took hundr$s ( ye>s to develop c
 be de/roy$  7photograph by ,t]r5ce     
,moore74    ,increas$ population &      
live/ock pressure on m>g9al l&s has     
accel]at$ des]tification4 ,9 "s areas1  
nomads mov+ to less arid  areas disrupt 
! local ecosy/em & increase ! rate (    
erosion (  ! l&4 ,nomads are try+ to    
escape ! des]t1 b because ( _!  l&-use  
practices1 !y are br++ ! des]t ) !m4    
,x is a misconception t dr\ghts cause   
des]tification4 ,dr\ghts are  common 9  
arid & semi>id l&s4 ,well-manag$ l&s c  
recov] f  dr\ght :5 ! ra9s return4      
,cont9u$ l& abuse dur+ dr\ghts1  h[ev]1 
increases l& degradation4 ,by #aigc1 !  
dr\ght t began 9  #aifh 9 ! ,sahel (    
,we/ ,africa & ! l&-use practices !re _h
  caus$ ! dea?s ( m ?an #ajj1jjj p & #ab
 million cattle1 z  well z ! disruption 
( social organizations f villages to !  
national level4    ,:ile des]tification 

has receiv$ trem5d\s publicity by !     
political  & news m$ia1 !re are /ill _m 
?+s t we don't "k ab\t !  degradation ( 
productive l&s & ! expansion ( des]ts4  
,9 #aihh  ,ridley ,nelson po9t$ out 9 an
 important sci5tific pap] t !           
des]tification problem & processes are n
 cle>ly def9$4 ,!re is  no cons5sus     
among rese>*]s z to ! specific causes1  
ext5t1 or  degree ( des]tification4     
,contr>y to _m popul> reports1          
des]tification is actually a subtle &   
complex process (  det]ioration t may   
(t5 be rev]sible4    ,illu/ration3 ,goat
 seeks food 9 ! sp>sely vegetat$ ,sahel 
( ,africa  7photograph c\rtesy ( !      
,u4,s4 ,ag5cy = ,int]national           
,developm5t74                           
,global monitor+    ,9 ! la/ #be ye>s1  
satellites h begun to provide ! global  
monitor+ necess>y = improv+ our und]/&+ 
( des]tification4  ,l&sat images ( !    
same area1 tak5 sev]al ye>s ap>t b dur+ 
! same po9t 9 ! gr[+ season1 may        
indicate *anges 9 !  susceptibility ( l&

 to des]tification4 ,/udies us+ ,l&sat  
data  help demon/rate ! impact ( p &    
animals on ! ,e>?4 ,h[ev]1  o!r types ( 
remote-s5s+ sy/ems1 l&-monitor+         
networks1 &  global data bases ( field  
obs]vations are ne$$ be=e ! process  &  
problems ( des]tification w be          
completely und]/ood4                    
,local rem$ies    ,at ! local level1    
individuals & gov]nm5ts c help to       
reclaim &  protect _! l&s4 ,9 areas ( s&
 dunes1 cov]+ ! dunes )  l>ge b\ld]s or 
petroleum w int]rupt ! w9d regime ne> ! 
face  ( ! dunes & prev5t ! s& f mov+4   
,s& f5ces are us$  ?r\gh\t ! ,middle    
,ea/ & ! ,unit$ ,/ates1 9 ! same way sn[
  f5ces are us$ 9 ! nor?4 ,placem5t (   
/raw grids1 ea* up to a  squ>e met] 9   
area1 w also decrease ! surface w9d     
velocity4  ,%rubs & trees plant$ )9 !   
grids are protect$ by ! /raw  until !y  
take root4 ,9 areas :]e "s wat] is      
available =  irrigation1 %rubs plant$ on
 ! l[] "o-?ird ( a dune's w9dw>d  side w
 /abilize ! dune4 ,?is vegetation       

decreases ! w9d  velocity ne> ! base ( !
 dune & prev5ts mu* ( ! s& f  mov+4     
,high] velocity w9ds at ! top ( ! dune  
level x (f &  trees c be plant$ atop ^! 
flatt5$ surfaces4    ,illu/ration3 ,/raw
 grids 7"o ( :i* is %[n above7 &        
vegetation  irrigat$ by wat] f ! ,yell[ 
,riv] /abilize dunes 9 ?is "p (  ,*9a's 
,t5gg] ,des]t 7%[n bel[7 & protect a    
ne>by railroad f  w9dbl[n s&4           
,illu/ration3 ,t5gg] ,des]t    ,oases & 
f>ml&s 9 w9dy regions c be protect$ by  
plant+ tree  f5ces or grass belts4 ,s& t
 manages to pass ?r\gh ! grass belts  c 
be caught 9 /rips ( trees plant$ z w9d  
breaks #ej to #ajj met]s  ap>t adjac5t  
to ! belts4 ,small plots ( trees may    
also be scatt]$  inside oases to        
/abilize ! area4 ,on a mu* l>g] scale1 a
 8,gre5  ,wall10 :i* w ev5tually /ret* m
 ?an #e1gjj kilomet]s 9  l5g?1 mu* long]
 ?an ! fam\s ,great ,wall1 is be+ plant$
 9  nor!a/]n ,*9a to protect 8s&y       
l&s0--des]ts believ$ to h  be5 creat$ by
 human activity4    ,m effici5t use (   

exi/+ wat] res\rces & control (         
sal9ization are o!r effective tools =   
improv+ arid l&s4 ,new  ways are be+    
s\ght to use surface-wat] res\rces su* z
 ra9 wat]  h>ve/+ or irrigat+ ) seasonal
 run(f f adjac5t highl&s4  ,new ways are
 also be+ s\ght to f9d & tap gr\ndwat]  
res\rces &  to develop m effective ways 
( irrigat+ arid & semi>id l&s4  ,rese>* 
on ! reclamation ( des]ts also is focus+
 on discov]+  prop] crop rotation to    
protect ! fragile soil1 on und]/&+ h[   
s&-fix+ plants c be adapt$ to local     
environm5ts1 & on h[  graz+ l&s & wat]  
res\rces c be develop$ effectively )\t  
be+ ov]us$4    ,illu/ration3 ,f wa/el&  
to v9ey>d4 ,gr\nd wat] & und]gr\nd      
*annels help ?is v9ey>d fl\ri% on l&    
reclaim$ f des]t  pavem5t 9 ,*9a's      
,turpan ,depression4    ,if we are to   
/op & rev]se ! degradation ( arid &     
semi>id  l&s1 we mu/ und]/& h[ & :y !   
rates ( climate *ange1  population gr[?1
 & food production adv]sely affect ^!   
environm5ts4 ,! mo/ effective int]v5tion

 c come only f !  wise use ( ! be/      
e>?-sci5ce in=mation available4         
,select$ ,read+s        ,bagnold1 ,r4   
,a41 #aida1 ,! physics ( bl[n s& & des]t
 dunes3    ,me?u51 ,london1 #bfe p4 7,a 
classic treatise conc]n+ ! orig9 &      
evolution ( dunes47      ,bre$1 ,c4 ,s41
 & o!rs1 #aigi1 ,regional /udies ( s&   
seas1 us+    ,l&sat 7,,erts7 imag]y3 9  
,mc,kee1 ,e4 ,d41 ed41 ,a /udy ( global 
s&    seas3 ,u4,s4 ,geological ,survey  
,pr(essional ,pap] #ajeb1 p4 #cje-cig4  
7,a    /udy ( select$ s& seas bas$ on   
analysis ( remote s5s+    images1       
surface w9d summ>ies1 & available       
lit]ature47      ,cook1 ,r4 ,u41 &      
,w>r51 ,&rew1 #aigc1 ,geomorphology 9   
des]ts3    ,univ]sity ( ,cali=nia       
,press1 ,b]keley1 ,cali=nia1 #cgd p4    
7,exam9es    ! nature ( l&=ms1 soils1 & 
geomorphological processes 9 !    _w's  
des]ts47      ,eigel&1 ,tor1 & o!rs1    
#aihb1 ,! des]t realm3 ,national        
,geographic    ,society1 ,wa%+ton1 #cjd 
p4 7,a well illu/rat$ discussion (      

des]ts    ( ,am]ica1 ,africa1 ,asia1 &  
,au/ralia47      ,ericks51 ,g4 ,e41     
#aihc1 ,! ,*ilean nitrate deposits3     
,am]ican    ,sci5ti/1 v4 #ga1 p4        
#cff-cgd4 7,a discussion ( ! orig9 ( !  
,*ilean nitrate deposits :i* has puzzl$ 
sci5ti/s = m ?an    #ajj ye>s47         
,g]/]1 ,georg1 #aifj1 ,sah>a-des]t (    
de/9y3 ,c[>d-,mc,cann1 ,new    ,york1   
#cjb p4 7,h[ plants1 animals1 & p       
survive 9 ! ,sah>a47      ,greeley1     
,ronald1 & ,iv]s51 ,j4 ,d41 #aihe1 ,w9d 
z a geological    process on ,e>?1 ,m>s1
 ,v5us & ,titan3 ,cambridge ,univ]sity  
,press1    ,new ,york1 #ccc p4 7,exp&s !
 classic "w ( ,bagnold to discuss       
eolian processes 9 a planet>y context4  
,describes ! processes on    all moons &
 t]re/rial planets ) atmosph]es47       
,h>e1 ,f4 ,k41 #aihc1 ,climate on !     
des]t fr+e3 9 ,g>dn]1 ,ritz1    &       
,scog+1 ,hel51 eds41                    
,mega-geomorphology3 ,cl>5don ,press1   
,ox=d1    p4 #acd-aea4 7,! m>g9s ( _m   
des]ts are affect$ by t5sion    betwe5  

society & environm5t4 ,?is pap]         
summ>izes ! climatology    ( arid       
zones47      ,mac,mahon1 ,james ,a41    
#aihe1 ,des]ts3 ,alfr$ ,a4 ,knopf1      
,inc41 ,new ,york1    #fdj p4 7,an      
,audubon ,society ,nature ,guide to !   
des]ts ( ! ,unit$    ,/ates1 & _!       
inhabitants47      ,mc,cauley1 ,j4 ,f41 
& o!rs1 #aihd1 ,remote monitor+ (       
processes t    %ape des]t surfaces3 ,!  
,des]t ,w9ds ,project3 ,u4,s4           
,geological    ,survey ,bullet9 #afcd1  
#ai p4 7,describes a new /udy on        
collect+    wea!r data f sol>-p[]$      
data-collection plat=ms 9 des]ts4    ,! 
data are relay$ by a ,,goes satellite to
 ! ,,usgs 9 ,flag/aff1    ,arizona1 &   
conv]t$ to graphic =m47      ,meigs1    
,pev]il1 #aiec1 ,_w di/ribution ( arid &
 semi-arid    homoclimates3 9 ,reviews (
 rese>* on arid zone hydrology3 ,p>is1  
,unit$ ,nations ,educational1           
,sci5tific1 & ,cultural ,organization1  
,arid ,zone ,programme-#a1 p4 #bjc-bji4 
7,classifies arid l&s accord+ to        

precipitation47      ,nelson1 ,r41      
#aihh1 ,dryl& managem5t3 !              
des]tification problem3    ,environm5tal
 ,dep>tm5t ,work+ ,pap] ,no4 #h1        
,wa%+ton3 ,_w ,bank1    #db p4 7,an     
excell5t review ( ! pres5t /ate ( k     
conc]n+ des]tification47      ,tolba1   
,m4 ,k41 #aihd1 ,des]tification is      
/oppable3 ,arid ,l&s    ,newslett] ,no4 
#ba1 p4 #b-i4 7,a discussion ( !        
problems involv$ 9    prev5t+           
des]tification & reclaim+ arid l&s47    
,walk]1 ,a4,s41 #aihf1 ,eolian          
geomorphology3 9 ,%ort1 ,n4,m41 &       
,blair1    ,r4,w41 eds41 ,geomorphology 
f space3 a global ov]view ( regional    
l&=ms3 ,,nasa ,,sp-#dhf1 p4 #ddg-ebj 7a 
brief review ( des]t    processes74     
,w>r51 ,a4 & ,agnew1 ,c41 #aihh1 ,an    
assessm5t ( des]tification &    l&      
degradation 9 arid & semi-arid areas3   
,int]national ,in/itute    = ,environm5t
 & ,developm5t1 ,dryl&s ,programme1     
,pap] #b1 ,london3    ,,ii$1 #ajc p4    
7,an evaluation ( l& degradation        

problems47          ,! metric units us$ 
9 ?is publication c be conv]t$ to       
,engli%  units by us+ ! approximate     
conv]sions giv5 bel[3      ,l5g?      #a
 kilomet]              #j4f ( a mile    
#a met]                   #ci4cg in*es  
#a c5timet]                  #j4d in*   
#a millimet]                 #j4jd in*  
,area      #a sq4 kilomet]              
#j4jd sq4 mile    #a sq4 met]           
#a4b sq4 y>ds    #a sq4 c5timet]        
#j4aee sq4 in*      ,temp]ature      ,to
 conv]t ,celsius to ,fahr5heit1 multiply
 ,c by #a4h & add #cb4    ,to conv]t    
,fahr5heit to ,celsius1 subtract #cb f  
,f & divide !            result by #a4h4
    ,illu/ration3 ,l&sat image %[s      
complex l9e> & cresc5tic dunes  9 !     
nor!a/]n ,taklimakan ,des]t ( ,*9a4     
,9 ?is des]t !re are a great _m evil    
spirits & also hot w9ds2  ^? :o enc\nt] 
!m p]i% to a man4 ,!re are nei!r birds  
above  nor bea/s bel[4 ,gaz+ on all     
sides z f> z ! eye c rea* 9  ord] to m>k
 ! track1 no guidance is to be obta9$   

save f !  rott+ bones ( dead m51 :i*    
po9t ! way4       ,explor] ,fa ,xian    
describ+ ! ,taklimakan ,des]t ( ,*9a    
ab\t #djj                               
,a4,d4          ,?is publication is "o (
 a s]ies ( g5]al int]e/ publications    
prep>$ by ! ,u4,s4 ,geological ,survey  
to provide in=mation ab\t !  e>?        
sci5ces1 natural res\rces1 & !          
environm5t4 ,to obta9 a  catalog (      
additional titles 9 ! s]ies 8,g5]al     
,int]e/  ,publications ( ! ,u4,s4       
,geological ,survey10 write3            
,u4,s4 ,geological ,survey      ,bran* (
 ,di/ribution      ,p4,o4 ,box #bebhf   
,d5v]1 ,,co #hjbbe     ,u4 ,s4          
,,gov]nm5t ,,pr9t+ ,,(fice 3 #aiib      
#j-ccb-cbf ,,ql #b      ,z ! ,nation's  
pr9cipal cons]vation ag5cy1 ! ,dep>tm5t 
( !  ,int]ior has responsibility = mo/ (
 our nationally-own$ public  l&s &      
natural & cultural res\rces4 ,?is       
includes fo/]+ wise  use ( our l& & wat]
 res\rces1 protect+ our fi% & wildlife1 
pres]v+ ! environm5tal & cultural values

 ( our national p>ks  & hi/orical       
places1 & provid+ = ! enjoym5t ( life   
?r\gh  outdoor recreation4 ,! ,dep>tm5t 
assesses our en]gy & m9]al  res\rces &  
works to assure t _! developm5t is 9 !  
be/  int]e/s ( all our p4 ,! ,dep>tm5t  
also promotes ! goals (  ! ,take ,pride 
9 ,am]ica campaign by enc\rag+ /ew>d%ip 
&  citiz5 responsibility = ! public l& &
 promot+ citiz5  p>ticipation 9 _! c>e4 
,! ,dep>tm5t also has a major           
responsibility = ,am]ican ,indian       
res]vation communities & =  p :o live 9 
,isl& ,t]ritories "u ,u4,s4             
,adm9i/ration4      ,cov] ,photographs3 
,illu/ration3 ,granite ,m\nta9 9 !      
,great ,bas9 ,des]t 7photograph by      
,t]r5ce ,moore74    ,illu/ration3       
,sonoran ,des]t 7photograph by ,pet]    
,kresan74    ,illu/ration3 ,zabriskie   
,po9t 9 ,dea? ,valley1 ,cali=nia        
7photograph  by ,pet] ,kresan74         
,illu/ration3 ,arti/s ,po9t 9 ,monum5t  
,valley 7photograph by ,pet]  ,kresan74 
,illu/ration3 ,dea? ,valley1 ,cali=nia  

7photograph by ,cecil  ,/\ghton74       
,illu/ration3 ,cacti 9 ! ,sonoran ,des]t
 7photograph by ,john ,olson74          
,illu/ration3 ,back ,cov]               
,transcrib]'s ,notes      --,correct$ a 
few typographical errors4    --,slightly
 displac$ photographs & captions = bett]
 display on    scroll+ e,book view]s4