,illu/ration3 ,cov]3 ,look+ s\?w>d along
 ,groton ,pond f ne>      ,/illwat]     
,brook4                                 
,,! ,,geology ,,(                       
,,groton ,,/ate ,,=e/                   
,by                            ,,rob]t  
,a4 ,,*ri/man                           
,,dep>tm5t ,,( ,,=e/s ,,& ,,p>ks        
,p]ry ,h4 ,m]rill1 ,director            
,,v]mont ,,developm5t ,,commission      
,,v]mont ,,geological ,,survey          
,*>les ,g4 ,doll1 ,/ate ,geologi/       
#aief                                   
,,geology ,,( ,,groton ,,/ate ,,=e/     
,by                            ,,rob]t  
,a4 ,,*ri/man                           
,,introduction      ,geology is ! /udy (
 ! hi/ory ( ! e>? z record$ 9 its       
rocks4 ,?is /udy expla9s :y c]ta9 types 
( rocks & m9]als occur  at "o place & n 
ano!r1 :y ! =ms ( ! l& diff] f "o       
region to ano!r1 & :y p>ticul> animal & 
plant rema9s are  sometimes pres]v$ z   
fossils 9 c]ta9 k9ds ( rocks4 ,!        
pr(essional geologi/ makes ^! /udies 8  

bus9ess2 ! amateur  f9ds ^! /udies a    
fasc9at+ hobby2 b ! un9itiat$ p]son     
misses mu* ( ! pleasure ( travel4       
,anyone :o notices ! diff]5ce  betwe5   
rocks or t]ra9s & wond]s 8:y801 has a   
pot5tial =  geology4 ,_m fall into ?is  
class & x is = !m t ?is booklet  has be5
 writt54 ,x is hop$ t ) its aid1 !      
travel] or  vacation] may come to "k    
some?+ ab\t ! geology ( ,groton ,/ate   
,=e/4 ,! au?or is confid5t t ^? :o come 
into ! habit (  obs]v+ nature & ! _w    
ar\nd !m w f9d m mean+ 9  life itself4  
,9 any case1 ^? travel+ ) *ildr5 may f9d
 answ]s  to "s ( _! que/ions ab\t       
m9]als1 rocks & m\nta9s4    ,groton     
,/ate ,=e/ is n a geologi/'s p>adise--z 
comp>$ to  ,yell[/one ,p>k or ! ,gr&    
,canyon--b x does conta9 int]e/+  rocks 
& l& =ms :i* c be expla9$ geologically4 
,9 keep+  ) ! calm1 subdu$ & mature     
atmosph]e ( ! ,v]mont c\ntryside1  !    
geology is unobtrusive4 ,!re are few    
jutt+ cliffs or b>e rock  exposures2 all
 is mantl$ ) vegetation4 ,if ?is        

vegetation c\ld be  /ripp$              
away--admitt$ly1 a po/ulation t w\ld    
de/roy !  wild]ness & *>m t belongs to  
,groton--b\ld]s & gravelly  glacial     
deposits w\ld be se5 to fill ! valleys4 
,if 9 turn ^!  b\ld]s & ! soil c\ld be  
/ripp$ away1 a cont9u\s floor ( rock    
w\ld be expos$4 ,?is w\ld be a          
geologi/'s p>adise--squ>e miles (  b>e  
rock w\ld be available = /udy4 ,h[ev]1  
lack+ ! magic w&  to p]=m ?is feat1 we  
mu/ be satisfi$ to glean :at in=mation  
we  c f ! exi/+ rock exposures4    ,to  
use a pun1 x c be said t almo/ all !    
rocks f\nd at ,groton  ,/ate ,=e/ c be  
tak5 = granite4 ,z well z has be5       
det]m9$1  all ! und]ly+ rock is         
granite#a & mo/ ( ! b\ld]s  deposit$ by 
glaci]s ( ! la/ ice age are ! same type 
( granite4  ,to avoid confusion 9       
describ+ ^! rocks1 ! discussion has be5 
divid$ into two p>ts3 ! fir/ deals ) !  
granite ( ! b$rock1  & ! second deals ) 
! glaciation ( ! area & ! deposits      
result+ f x4 ,a ?ird section describes !

 geology 9 "s ( !  ne>by areas4         
,,granite ,,& ,,relat$ ,,rocks          
,occurr5ce ( ! granite    ,l$ges (      
light-color$ granite occur at ! summits 
( mo/ ( !  m\nta9s & hills 9 ! ,/ate    
,=e/ area & are f\nd occasionally  at   
l[] elevations4 ,!y are conspicu\s on   
,owl%ead1 ,silv] ,l$ge1  ,little ,de]1  
,big ,de]1 ,nigg]head & ,spic] ,m\nta9s2
 small] l$ges  also occur on ,kettle1 & 
,little ,spruce m\nta9s1 ,h>dwood ,ridge
 &  ! l[ hills ea/ ( ,groton ,pond4 ,at 
l[] elevations1 granite is f\nd  at !   
outlet ( ,groton ,pond1 along ! railroad
 tracks we/ ( ,groton  ,pond & at       
,/illwat] ,brook1 along ,osmore brook & 
at sev]al o!r  m9or locations4 ,^!      
locations are %[n diagrammatically on ! 
map  by a black dot4 ,^! dots indicate  
:]e ! granite occurs b no?+  ab\t !     
ext5t ( ! exposure4 ,if e location (    
expos$ rock 7  m>k$ ) a dot1 c]ta9 p>ts 
( ! map1 = in/ance1 ! we/ side  (       
,nigg]head1 w\ld be solid black & !     
cont\r l9es :i* %[ !  elevation w\ld be 

obscur$ completely4    ,all ^! rocks are
 presumably "p ( "o l>ge mass ( granite 
:i*  ext5ds deep bel[ ! surface ( ! e>?4
 ,mo/ ( ?is body (  granite is hidd5 by 
! soil & b\ld]y glacial deposits1 s t   
its  exact areal ext5t is n kn[n4 ,x    
appe>s likely t x ext5ds to  ! s\?we/ to
 ! vic9ity ( ,ea/ ,b>re4                
,description ( ! granite    ,! granite  
f\nd at ,groton ,/ate ,=e/ is a gray to 
:ite1  m$ium-gra9$ rock ) ! m9]al gra9s 
all ab\t ! same size4  ,surfaces expos$ 
to wea!r+ are g5]ally d>k] 9 color &    
frequ5tly are cov]$ ) scales ( d>k      
color$ li*54 ,if ! rock  is brok5 to    
reveal an unalt]$ surface close         
exam9ation w disclose  individual m9]al 
gra9s ( mica1 feldsp> & qu>tz4 ,mica    
occurs z  v small plates :i* appe> ei!r 
:ite or colorless1 call$  muscovite1 or 
z black %9y plates call$ biotite4 ,!    
feldsp>1  :i* is ! mo/ abundant m9]al 9 
! granite1 has a *alky :ite  appe>ance &
 may occur z tabul> gra9s :i* reflect   
light f  _! flat surfaces :5 held 9 !   

prop] position4 ,qu>tz1 :i*  conta9s    
only silicon & oxyg51 ! two mo/ common  
elem5ts 9 !  e>?'s cru/1 is a transp>5t1
 glassy m9]al :i* has no flat  surfaces4
 ,x may appe> gray because "o c look d[n
 into ! glassy  m9]al :]e !re is no     
light s\rce4    ,a specim5 ( granite f  
,owl%ead 0 /udi$ ) a microscope aft]  x 
_h be5 cut & gr\nd to a ?ickness ( only 
#j4jc millimet]s4 ,_m  m9]als1 :i*      
ord9>ily appe> to be opaque1 are        
transp>5t :5  gr\nd ?is ?94 ,by _! v>i\s
 optical prop]ties1 ! diff]5t  m9]als c 
be id5tifi$ & ! composition ( ! rock c  
be  det]m9$4 ,figure #a %[s a           
photograph1 tak5 ?r\gh a microscope1 (  
"o ( ^! ?9 sections ( granite4 ,by      
c>eful exam9ation ( !  ?9 section & by  
measur+ ! areal ext5t ( ! diff]5t m9]als
  pres5t1 ! rock 0 det]m9$ to conta91 by
 volume1 #ce p]c5t  qu>tz1 #fj p]c5t    
feldsp> 79 proportions ( #be p]c5t      
microcl9e  feldsp>1 ,k,al,si,o & #ce    
p]c5t plagioclase feldsp>1 ,na,al,si,o7 
&  #e p]c5t mica 79 proportions ( #d    

p]c5t biotite & #a p]c5t  muscovite74   
,al?\gh x is a memb] ( ! granite family1
 ?is rock  %\ld1 9 /rict t]m9ology1 be  
call$ a qu>tz monzonite r ?an  a granite
 to indicate m precisely ! m9]al        
composition4 ,because (  slight         
diff]5ces 9 composition1 granite f !    
same body may  else:]e be correctly     
call$ granodiorite1 qu>tz diorite or    
granite  prop]1 dep5d+ on ! relative    
am\nts ( ! two feldsp>s &  qu>tz4 ,9 ?is
 report ^! close di/9ctions h n be5 made
 &  ! rock is simply call$ granite4     
,cracks 9 ! granite    ,two k9ds (      
natural breaks1 or cracks1 occur 9 !    
granite 9 !  ,/ate ,=e/ area4 ,jo9ts are
 breaks :i* occur along plane surfaces  
& exfoliation is ! "n giv5 to ! breakage
 along curv$  surfaces relat$ to !      
exposure ( ! rock4 ,granite1 z contra/$ 
) o!r rocks1 is *>act]iz$ by its        
uni=mity ( texture &  massiv5ess1 s t   
any cracks pres5t are conspicu\s4       
,illu/ration3 ,figure #a4               
,photomicrograph ( a ?9 section (       

granite f ,owl%ead ,m\nta94 ,! m9]al ) !
 grid patt]n      7upp] left7 is a      
feldsp> nam$ microcl9e :i* has !        
composition ( ,k,al,si,o4 ,! "o ) !     
indi/9ct /rip$ patt]n      7l[] c5t]7 is
 a feldsp> nam$ plagioclase1 v>iety     
oligoclase1      :i* has ! composition (
 approximately ,na,al,si,o4 ,! patt]ns  
= ^! m9]als result f diff]5t portions ( 
! same      m9]al gra9 hav+ diff]5t     
ori5tations1 call$ tw9n+1 s z      to   
give a diff]5t optical appe>ance4 ,!    
cle> :ite m9]al      7"r c5t]7 is qu>tz4
 ,! d>k gray m9]al ) ! f9e l9es         
7upp] c5t]7 is biotite & ! small]1      
light]-color$1 elongate      m9]al to ! 
"r ( ! biotite is muscovite4 ,! o!r     
m9]als      are feldsp> & qu>tz 9       
diff]5t ori5tations4 ,! actual          
diamet] ( ! cle> :ite qu>tz gra9 7"r    
c5t]7 is ab\t      f\r-t5?s ( a         
millimet] s t ! photograph is a         
magnification ( ab\t "o hundr$4         
,jo9ts are m conspicu\s ( ! two types1 &
 typically belong to a  g5]al sy/em s t 

at a giv5 location !y t5d to be p>allel4
 ,on  top ( ,owl%ead1 = example1 ! mo/  
prom95t jo9ts tr5d ,n4#be,w4  7read3    
,nor? tw5ty-five degrees to ! we/7 )    
dips#b t are  v]tical or dipp+ /eeply to
 ! s\?we/4 ,ano!r set ( jo9ts  tr5ds    
,n4#aj;,e4 ) dips t are v]tical or dipp+
 /eeply to !  s\?we/4 ,jo9ts repres5t ! 
breakage ( ! rock due to /ress &  /ra94 
,"s jo9ts result f t5sional =ces set up 
)9 ! rock  itself by contraction due to 
cool+ ( ! orig9ally hot solidifi$  rock4
 ,o!r jo9ts result f l>g]-scale =ces )9 
! e>?'s  cru/ :i* cause e>?quakes &     
g5]al movem5t ( l& masses4 ,an          
exhau/ive /udy ( all ! rocks 9 a l>ge   
area w\ld be requir$ to  det]m9e        
conclusively ! orig9 ( ! jo9ts on       
,owl%ead4    ,9 addition to ! ne>ly     
v]tical jo9ts1 a ?ird set ( ne>ly       
horizontal jo9ts may be obs]v$ on       
cliffs4 ,^! jo9ts are call$  %eet+ &    
app>5tly are relat$ to ! dep? f a =m]   
topographic surface :i* exi/$ at ! "t ! 
%eet+ orig9at$4  ,! v]tical jo9ts &     

%eet+ are important qualities ( a rock  
to be  consid]$ 9 *oos+ a rock =        
comm]cial qu>ry+4 ,n only d  ^! factors 
effect ! ease ( qu>ry+1 b !y also       
det]m9e !  am\nt ( wa/e mat]ial :i* w\ld
 h to be remov$ & disc>d$  because (    
poor size & %ape4    ,exfoliation is !  
t]m = breakage due to ! dis9tegration   
caus$ by  decomposition ( ! rock on     
surfaces expos$ to ! wea!r4 ,x is       
*>act]iz$ by ! scal+ (f ( conc5tric     
%ells ( alt]$ rock to  produce a convex 
surface4 ,rocks %[+ exfoliation surfaces
 are n  common at ,groton4 ,"o ( ! be/  
develop$ exfoliation surfaces1          
illu/rat$ 9 ,figure #b1 occurs at ! base
 ( ! cliffs on ! s\?  side ( ,owl%ead   
,m\nta94    ,once jo9ts h =m$1 !y are   
enl>g$ by wea!r+4 ,9 p>ticul>1  rocks   
are pu%$ ap>t by a 8fro/ w$g+40 ,:5 wat]
 freezes x  exp&s by ab\t "o-t5? ( its  
volume4 ,if x is conf9$ x may ex]t  a   
pressure ( z mu* z #ach tons p] squ>e   
foot4 ,9 ?is mann]1 huge  blocks may be 
pu%$ ap>t4 ,if !y are at ! edge ( a     

cliff1 or "p  ( ! cliff itself1 !y may  
ev5tually break (f & fall to ! slope    
bel[4 ,! accumulation ( brok5 rock at ! 
base ( a cliff is call$  talus4         
,orig9 & age ( ! granite    ,! granite  
orig9at$ 9 ! int]ior ( ! e>? _m million 
ye>s  ago z a molt5 mass1 call$ magma4  
,?is magma mov$ upw>d ?r\gh  ! e>?'s    
cru/ by a process ( melt+ ! pre-exi/+   
rock or by  =cefully pu%+ x aside4 ,:5 x
 rea*$ its pres5t position x  became    
cool] & m9]als began to cry/allize out4 
,h[ev]1 z is  %[n 9 ,figure #c1 x is    
important to und]/& t ! surface ( !  l& 
0 n 9 its pres5t position & t ! magma   
actually cool$  b5ea? a consid]able     
?ickness ( o!r rocks4 ,^! ov]ly+ rocks1 
n[ gone1 act$ z an insulator & prev5t$ !
 magma f cool+ too  quickly4 ,if ! magma
 _h ris5 ?r\gh ^! rocks & rea*$ _!  upp]
 surface1 x w\ld h =m$ a lava fl[ simil>
 to ^? (  pres5t-day volcanoes & w\ld h 
cool$ mu* m rapidly4 ,rocks  =m$ ne> !  
surface are *>act]iz$ ei!r by be+       
f9e-gra9$  )\t visible cry/als or by    

hav+ a few l>ge cry/als 9 a  f9e-gra9$  
matrix2 !y nev] h a uni=mly1            
m$ium-to-co>se-gra9$ texture4 ,?us1 !   
texture ( ! granite at  ,groton ,/ate   
,=e/ proves t x cool$ sl[ly & indicates 
t1 at  ! "t ( cool+1 ! granite 0 n at ! 
surface4 ,?is is a  reasonable          
po/ulation because /udies ( ! regional  
geology indicate  t a l>ge am\nt ( rock 
has be5 remov$ f ?is area by erosion    
?r\gh ! long p]iods ( geologic "t4      
,illu/ration3 ,figure #b4 ,exfoliation  
surface on ! s\? side (      ,owl%ead   
,m\nta94 ,jo9ts1 ( ! %eet+ type1 are    
visible 9 !      granite cliff4 ,!      
decomposition ( ! granite by wea!r+ 9 ! 
ni*es has result$ 9 small pat*es ( soil4
 ,! boy 9 ! upp]      "r gives ! scale4 
,illu/ration3 ,figure #c4 ,sequ5ce (    
ev5ts at ,groton ,/ate ,=e/      %[n    
diagrammatically4        ,illu/ration3  
,a4 ,! ,waits ,riv] ,=mation & o!r y\ng]
      =mations are deposit$ f a %all[   
sea dur+ ,ordovician "t4      ,,y\ng]   
,,=mations    ,,waits ,,riv] ,,=mation  

,illu/ration3 ,b4 ,! s$im5t>y rocks are 
fold$ & metamorphos$      & ! granite is
 intrud$ into ! old] rocks & cry/allizes
      dur+ ,devonian "t4      ,,waits   
,,riv] ,,=mation    ,,granite           
,illu/ration3 ,c4 ,erosion removes mu* (
 ! rock f ! area4      ,,granite        
,illu/ration3 ,d4 ,dur+ ! ice age1      
cont95tal glaci]s move ov]      ! l& &  
erosion by ! ice =ms ,owl%ead ,m\nta9 & 
!      bas9 = ,groton ,pond4      ,,ice 
,,granite        ,illu/ration3 ,e4      
,pres5t topography1 exagg]at$4          
,,owl%ead ,,m\nta9    ,,rick] ,,mills   
,evid5ce t ! granite 0 emplac$ into !   
old] rocks ( !  e>?'s cru/ c be se5 at  
c]ta9 locations outside ( ! ,/ate  ,=e/4
 ,at ,rick] ,mills1 = example1 n>r[     
bodies ( granite c be  se5 cross cutt+ !
 old] rocks4 ,a full] description ( !   
geology  at ,rick] ,mills is giv5 9 a   
lat] section ( ?is report4 ,ano!r type  
( evid5ce %[+ t ! granite came into old]
 rocks is f\nd 9  ! occurr5ce ( fragm5ts
 ( old] rock incorporat$ into ! granite4

  ,^! are call$ inclusions & repres5t   
brok5 pieces ( old] rock  :i* 7 envelop$
 by ! granite4 ,inclusions are l pea*   
slices 9  jello 9 t ! surr\nd+ mat]ial  
solidifi$ aft] !y 7  dropp$ 94          
,inclusions 7 obs]v$ 9 rocks on top (   
,kettle & ,j]ry  ,lund ,m\nta9s4    ,ne>
 ! cov]$ picnic %elt] at ,rick] ,pond1  
"o ( ! l>ge granite  b\ld]s deposit$ by 
! glaci] conta9s inclusions4 ,al?\gh ?is
  b\ld] has be5 mov$ f its orig9al      
occurr5ce1 x probably has n  mov$ f> z x
 is compos$ ( ! :ite granite :i* is     
typical ( !  area4 ,x is cut by sev]al  
pegmatitic dikes4 ,! mo/ int]e/+        
feature is ! occurr5ce ( inclusions (   
elongate1 lay]$ b&s (  old] rocks ( gray
 to d>k gray s*i/4#c ,^! relations are  
%[n  9 ! sket* ( ?is b\ld] 9 ,figure #d4
 ,a c>eful exam9ation ( !  s*i/         
inclusions reveals t !y conta9 small    
plates ( biotite 9 a  f9e matrix ( qu>tz
 & m mica4 ,! contact betwe5 ! s*i/ &   
granite is gradational at places because
 :5 ! rock 0 =m$ !  hot molt5 granite 0 

9 ! process ( melt+ ! solid s*i/4 ,!    
s*i/ resembles ! rock :i* occurr$ 9 ?is 
area be=e ! granite  0 intrud$ & :i*    
occurs 9 ne>by areas :]e no granite is  
expos$4 ,old] rocks ( some:at simil>    
appe>ance c be se5 at  ,rick] ,mills &  
on top ( ,j]ry ,lund ,m\nta94    ,!     
composition ( ! granite at ,groton ,/ate
 ,=e/ is ne>ly ! same  z t :i* occurs   
?r\gh\t ?is region ( ,v]mont4           
,incomplete  mapp+ sugge/s t ! granite  
at ,groton is "p ( a l>ge mass  :i*     
ext5ds to ! s\?we/ to ! vic9ity ( ,ea/  
,b>re4  ,und\bt$ly all ! granitic rocks 
( ?is region are relat$ al?\gh  !y are n
 cont9u\s at ! surface4 ,!y 7 all       
emplac$ at ab\t  ! same "t foll[+ a     
m\nta9-build+ episode 9 :i* ! old]      
rocks 7 fold$ & metamorphos$4 ,on !     
geologic "t scale1 !  granites 7 emplac$
 ne> ! end ( ! ,devonian p]iod :i* is   
e/imat$ to be m ?an #cjj million ye>s   
ago4        ,illu/ration3 ,figure #d4   
,sket* ( b\ld] ( granite conta9+        
pegmatite b& & s*i/ inclusions at picnic

 area at ,rick] ,pond4      ,,granite   
,,pegmatite    ,,s*i/      ,aplite &    
pegmatite    ,two o!r types ( igne\s    
rocks call$ aplite & pegmatite occur    
sp>+ly 9 ,groton ,/ate ,=e/4 ,bo? ( ^!  
are productions (  cry/allization (     
residual fluids or late /age magma      
relat$ to !  granite4 ,^! 7 emplac$     
along cracks or planes ( weakness 9 !   
granite aft] ! granite _h solidifi$4 ,:5
 view$ f ! surface  ! aplite or         
pegmatite g5]ally appe> z b&s cutt+     
?r\gh !  granite4 ,h[ev]1 :5 !          
?ird-dim5sion is consid]$ x is easily   
realiz$ t !y are tabul> or %eet-l 9     
%ape4 ,igne\s rock  masses hav+ ^!      
dim5sions are call$ dikes4 ,at ,groton  
mo/ ( !  dikes are ne>ly v]tical ) a    
?ickness rang+ f less ?an an  in* to m  
?an sev]al feet & ext5d+ = consid]able  
di/ances4  ,on ,owl%ead1 "o ( ^! dikes  
is ne>ly ?ree feet ?ick4 ,! ext5t  ( ^! 
dikes is n kn[n because !y are only     
p>tly expos$1 9  t !y ext5d beyond !    
limit$ areas ( rock exposure4           

,illu/ration3            ,,groton ,,/ate
 ,,=e/        ,,drew ,,mtn              
,,nigg]head ,,mtn      ,,blake ,,hill   
,,nigg]head ,,brook      ,,kettle ,,mtn 
,,spic] ,,mtn      ,,owl%ead ,,mtn      
,,kettle ,,pond      ,,/illwat] ,,bk4   
,,h>dwood ,,ridge      ,,beav] ,,brook  
,,silv] ,,l$ge      ,,little ,,spruce   
,,mtn      ,,pea*am ,,pond      ,,de]   
,,mtn      ,,devil',s ,,hill            
,,pea*am ,,bog      ,,little ,,de] ,,mtn
      ,,osmore ,,bk4      ,,coldwat]    
,,bk4      ,,groton ,,pond      ,,j]ry  
,,lund ,,mtn      ,,rick] ,,pond        
,,rick] ,,mills    ,,explanation        
,,granite ,,exposures      ,,s*i/       
,,exposures      ,,trail      ,,railroad
      ,,swampy ,,areas      ,,cont\r    
,,l9e ,,) ,,elevation      ,,cont\r     
,,int]val ,,is #ajj ,,feet              
,,topography ,,f ,u4 ,s4 ,,geological   
,,survey ,,maps        ,,by ,,rob]t     
,,*ri/man    ,! pegmatite dikes are     
co>se-gra9$1 9 "s cases consi/+ (       
individual m9]al gra9s z mu* z two to   

f\r in*es 9 diamet]4 ,!  m9]al          
composition ( ! pegmatites is ne>ly !   
same z ! granite1  except t biotite is  
usually abs5t4 ,because ( _! l>g] gra9  
size1 ! m9]als c be recogniz$ m easily 9
 pegmatites ?an 9  ei!r granite or      
aplite4 ,qu>tz is glassy & breaks )     
smoo? curv$  fractures4 ,feldsp> is     
*alky :ite1 or p9k1 & may occur z tabul>
  cry/als ) /raight-l9e contacts4 ,x    
t5ds to break along def9ite  int]sect+  
planes :i* c be se5 9 _! reflect+       
position4  ,muscovite occurs z 8books0 (
 semi-transp>5t leaves4 ,! l>ge  8books0
 ( muscovite are p>ticul>ly int]e/+     
because ( !  fasc9at+ fact t a m9]al    
%eet c be split along a giv5 plan>      
direction into ?9n] & ?9n] %eets until  
!y are too ?9 to  h&le4 ,!oretically !  
m9]al might be split into %eets only z  
?ick z "o lay] ( atoms4 ,! ability ( a  
m9]al to break along  def9ite planes is 
relat$ to its atomic /ructure & is call$
  cleavage4 ,! cleavage 9 mica is       
p]fect1 :]eas ! cleavage 9  feldsp> is  

only poorly develop$1 & qu>tz does n    
possess cleavage  at all4    ,! aplite  
dikes are compos$ ( ne>ly ! same m9]als 
z granite  except t ! av]age gra9 size  
is small]4 ,!y are *>act]iz$ by  !      
abs5ce ( d>k m9]als & muscovite & by a  
high qu>tz cont5t  :i* gives ! rock a   
8sug>y0 appe>ance4 ,mo/ ( ! aplite dikes
 are  less ?an six in*es ?ick4          
,inasmu* z ! pegmatite & aplite dikes   
bo? cut ?r\gh ! granite1  !y bo? mu/ be 
y\ng] 9 age ?an ! granite4 ,z is %[n by 
!  relations betwe5 ^! two types on     
,owl%ead 7reproduc$ 9 ,figure #e71  !   
pegmatite dike is y\ng] because x cuts  
across ! aplite dike4  ,?is is ! g5]al  
age relation%ip = ^! dikes 9 ?is age4   
,illu/ration3 ,figure #e4 ,sket* %[+    
aplite & pegmatite dikes      9 !       
granite on ,owl%ead ,m\nta94 ,! cross   
cutt+ relations      %[ t ! pegmatite is
 y\nge/ & t aplite is y\ng] ?an      !  
granite b old] ?an ! pegmatite4 ,9 !    
di/ance is ,kettle      ,pond & ,kettle 
,m\nta94      ,,granite    ,,aplite     

,,pegmatite                             
,,glaciation      ,al?\gh ! causes ( !  
ice ages rema9 a matt] = conjecture1 !  
fact is e/abli%$ t ! nor!rn "p ( ,nor?  
,am]ica 0 cov]$  by a ?ick %eet ( mov+  
ice sev]al diff]5t times beg9n+ ab\t a  
million ye>s ago4 ,z ! effect ( ! la/   
glaciation eras$ mu* (  ! evid5ce (     
previ\s glaciations1 ! pres5t topography
 c be  relat$ to t la/ "o4 ,r accurate  
dat+ by measur+ !  radioactive decay (  
,c>bon #ad1 indicates t ! ice ( ! la/   
glaciation retreat$ f ! area ab\t       
#ab1jjj ye>s ago4 ,because !  climates  
betwe5 ! f\r glaciations 7 z w>m1 if n  
w>m]1 ?an  our pres5t-day climate1      
geologi/s h speculat$ t ! _w may  n[ be 
9 a w>m p]iod & t ano!r ice age is      
s*$ul$ to occur  "s "t 9 ! di/ant       
future4    ,! effect ( cont95tal        
glaciation ^u a l& mass is tw(old4      
,fir/1  ! glaciation acts z an erosive  
ag5t :i* t5ds to scoop out !  areas (   
s(t] rock & we> d[n ! areas ( m resi/ant
 rock4  ,secondly1 :5 ! glaci] beg9s to 

melt1 x drops l>ge quantities (  gravel 
& b\ld]s :i* _h become incorporat$ )9 ! 
glaci]4  ,mo/ ( ?is mat]ial is pick$ up 
by ! glaci] z x moves ov] !  l&2 "s     
falls onto ! glaci] :]e x occupies a    
valley4 ,"s (  ! s&1 gravel & b\ld]     
deposits left by ! glaci] are  di/9ctive
 9 =m & composition & o!rs are *>act]iz$
 by  _! complete lack ( di/9ctive %apes1
 & ! utt]ly *aotic  nature ( ! mat]ial  
deposit$4 ,! deposits at ,groton ,/ate  
,=e/  seem to be ! latt] type4          
,erosion & deposition by ! glaci]    ,! 
%ape ( ,spic]1 ,owl%ead1 ,little ,de] & 
,big ,de] m\nta9s are  prim>ily ! result
 ( ! erosive action ( ! glaci] z x      
cont9ually mov$ s\?w>d ov] ! l& = a     
great numb] ( ye>s  dur+ ! la/          
glaciation4 ,:5 a cont95tal glaci]      
enc\nt]s a hill  or m\nta9 ( resi/ant   
rock1 x t5ds to sc\r ! rock on ! up-ice 
side ( ! hill & to 8pluck out0 ! rocks  
on ! leew>d side4 ,=  ?is reason ^!     
m\nta9s h broad g5tle slopes on ! side f
  :i* ! glaci] came & !y drop (f %>ply  

on ! side f :i*  mat]ial 0 remov$ by    
pluck+ action4 ,! la/ "p ( ,figure #c   
illu/rates h[ ^! m\nta9s may h be5 =m$4 
,su* prom95t  rock exposures :i* h be5  
subject$ to glacial erosion orig9ally   
%[$ deep scrat*es1 call$ glacial /riae1 
cut by cobbles dragg$  along ! bottom ( 
! glaci]4 ,un=tunately1 on mo/ prom95ces
 9  ,groton ,/ate ,=e/ exfoliation ( !  
rock has eras$ ^! m>k+s2  b x is        
possible t /riae may be f\nd on rec5tly 
uncov]$ rock  exposures4    ,!          
depressions 9 :i* ,groton & ,osmore     
ponds are locat$ probably  repres5t     
areas 9 :i* ! glaci] scoop$ out mat]ial 
to a great]  dep? ?an else:]e ei!r      
because ( *annel+ ( bottom fl[ betwe5   
topographically prom95t features1 or    
because ( subtle diff]5ces 9  rock      
h>dness4    ,:5 ! glaci] retreat$1 t is 
:5 x 0 melt+ fa/] ?an x  0 advanc+1 x   
dropp$ mat]ial 9 a helt]-skelt] mann]4  
,end  mora9es1 :i* are ridges ( gravel  
=m$ :]e ! front ( !  glaci] 0 /ation>y  
because ( a close balance betwe5 rates (

  movem5t & melt+1 are n evid5t 9       
,groton ,/ate ,=e/4 ,z f> z  c be       
det]m9$1 ! mat]ial 0 deposit$ irregul>ly
 ov] !  entire area1 s t b\ld]s dropp$  
by ! glaci] are f\nd  ev]y:]e4 ,^! are  
p>ticul>ly noticeable ar\nd ! lakes :]e 
!  f9e mat]ial has be5 remov$ & ! soil &
 =e/ cov] does n  hide ! b\ld]s4        
,almo/ all ( ! b\ld]s deposit$ by !     
glaci] are compos$ (  :ite granite      
simil> to ! rock :i* und]lies ! entire  
area4 ,?is  indicates t mo/ ( ! b\ld]s h
 n be5 transport$ v f>4  ,h[ev]1        
occasionally b\ld]s are f\nd :i* are n  
*>act]i/ic (  ! area & repres5t rocks   
br\ght 9 f ! nor?4 ,su* b\ld]s  :i* are 
=eign to ! area 9 :i* !y are f\nd are   
call$  erratics4 ,mo/ erratics 9 ?is    
area are d>k-color$ metamorphos$  rocks 
9 :i* ! m9]als are ori5t$ to give ! rock
 a lay]$  patt]n4 ,^! are call$ ei!r    
gneisses or s*i/s dep5d+ on  :e!r !     
lay]+ is co>se or f9e4 ,deposits ( !    
glaci] are  expos$ 9 two gravel or s&   
pits ne> ! ,/illwat] ,camp site4 ,^!    

deposits are compos$ pr9cipally ( s& b  
conta9 scatt]$ b\ld]s  ( diff]5t sizes4 
,a few erratics are f\nd 9 ^!           
deposits--p>ticul>ly a v>iety ( rock :i*
 wea!rs to a s(t1 br[n  por\s mass      
resembl+ decay$ wood4 ,^! s&y deposits  
probably 7  pla/]$ onto ! gr\nd f ! sole
 ( ! creep+ glaci] or 7  simply let d[n 
z ! glaci] wa/$ away4    ,because ( !   
irregul> mann] 9 :i* ! glaci] may       
deposit its  load ( s& & gravel1 !      
topography 9 su* areas is unev5 &       
*>act]iz$ by poor dra9age4 ,at a numb] (
 places 9 ,groton swampy  areas occur at
 high] elevation :i* might normally be  
expect$ to be  well-dra9$4 ,"s ( ^!     
areas h become ! sites ( beav] dams     
because !y are ideal = damm+ up ! wat]4 
,,geology ,,( ,,ne>by ,,areas           
,rick] ,mills    ,j s\? ( ! p>k at      
,rick] ,mills "s ( ! olde/ rocks 9 !    
area are expos$ 9 ! railroad cut j nor? 
( ! highway cross+4  ,^! rocks belong to
 a ?ick sequ5ce ( simil> rocks :i* are  
collectively call$ ! ,waits ,riv]       

=mation4 ,/udies 9 o!r areas  indicate t
 ^! rocks belong to ! portion ( geologic
 "t call$  ! ,ordovician p]iod :i* 0 m  
?an #cej million ye>s ago4    ,! ,waits 
,riv] =mation repres5ts a s]ies (       
s$im5ts :i*  accumulat$ at ! bottom ( a 
%all[ sea dur+ ,ordovician "t4 ,^!      
s$im5ts includ$ bo? limy & s&y b$s1 &   
fossils may orig9ally  h be5 pres]v$ 9  
"s ( ! b$s4 ,s$im5ts ( o!r types lat]   
accumulat$ ov] ! ,waits ,riv] =mation   
dur+ a long p]iod (  geologic "t1 s t   
ev5tually ! =mation became deeply buri$4
  7,see ,figure #c47 ,! sea retreat$ & !
 rocks 7 subject$ to high  pressure &   
temp]atures dur+ a p]iod (              
m\nta9-build+4 ,!  rocks :i* _h be5     
s$im5t>y 7 fold$ & conv]t$ to           
metamorphic rocks by p>tial melt+ &     
recry/allization ( !  compon5ts4 ,z a   
result ! rocks became s*i/s or m>bles4  
,any fossils  :i* may h be5 pres5t 7    
de/roy$ or badly alt]$ 9 !  process4    
,?is is un=tunate because valuable      
geologic in=mation z  ! age ( ! rocks c 

be det]m9$ f ! type ( fossils pres5t4   
,! rocks ( ! ,waits ,riv] =mation at    
,rick] ,mills are dom9antly  mica s*i/s 
) lay]s conta9+ limy mat]ial4 ,^! are   
too impure  to be consid]$ m>ble b en\gh
 lime is pres5t s t !y react  /rongly ) 
acid1 a te/ = detect+ ! pres5ce ( lime4 
,!  s*i/s pr9cipally conta9 qu>tz1      
biotite1 calcite 7lime7 ) less]  am\nts 
( muscovite1 feldsp> & impurities4 ,!   
rocks wea!r to d>k  colors2 ! gray limy 
b$s are p>ticul>ly susceptible to wea!r+
  & turn d>k br[n to black on ! surface4
 ,:5 m lime is pres5t1  ! rock wea!rs to
 a deep br[n por\s rock :i* resembles   
decay$  wood4 ,"s b\ld]s ( ^! alt]$     
lime/ones are f\nd 9 ! glacial  deposits
 9 ! ,/ate ,=e/4    ,an additional      
factor :i* makes ! rocks 9 ! railroad   
cut at ,rick]  ,mills look 8messy0 is ! 
iron & manganese /a9+ & ! =mation  (    
m9]al cru/s on ! surface ( ! rocks ?r\gh
 ! action (  gr\nd wat]4 ,ra9 wat] fall+
 on ! hills above passes ?r\gh !  soils1
 dissolv+ m9]als1 & precipitat+ !m :]e !

 wat] seeps  out & evaporates at ! l[]  
level ( ! railroad tracks4    ,! s*i/s  
tr5d ab\t ,n4#hj,w4 & dip ab\t #cj to ! 
nor!a/4  ,along ! l5g? ( ! rock         
exposures x c be se5 t ?is dip is  n    
con/ant b v>ies f #aj to #cj4 ,!        
v>iation 9 dip gives !  s*i/s a wavy    
appe>ance4    ,at two places along !    
railroad cut1 ! s*i/ has be5 intrud$ by 
granite4 ,z is %[n 9 ,figure #f1 :i* is 
a sket* ( ! rocks expos$  on ! ea/ side 
( ! railroad1 ! granite =ms v]tical     
dikes4 ,z  ! s*i/ ends abruptly at !    
contact ( ! granite1 ?is indicates  t ! 
granite =m$ aft] ! s*i/4 ,! granite is  
ne>ly ! same  z ! granite 9 ,groton     
,/ate ,=e/ except t ! mica is muscovite 
r ?an biotite4 ,= ?is reason ! granite  
is light] 9 color on  fre% surfaces4 ,9 
g5]al ! ext]ior is d>k 9 color due to ! 
/a9+ ( iron f wea!r+ ( ! m9]al pyrite1  
an iron sulfide1  :i* occurs 9 small    
am\nts 9 ! granite4      ,j]ry ,lund    
,m\nta9    ,on top ( ,j]ry ,lund ,m\nta9
 occur o!r outcrops ( ! ,waits ,riv]    

=mation & granite4 ,_! exact            
relation%ips _c be se5 easily  because (
 ! ?ick vegetation4 ,! ,waits ,riv]     
=mation on ,j]ry ,lund  ,m\nta9 is      
compos$ pr9cipally ( qu>tz mica s*i/4   
,,trips ,,to ,,take      ,hik+ 9 ! ,/ate
 ,=e/    ,! hike f ! end ( ! road to !  
top ( ,owl%ead ,m\nta9 takes  only t5 to
 fifte5 m9utes4 ,a spl5did view ( !     
surr\nd+ area1  p>ticul>ly ,groton &    
,kettle ponds1 is obta9$ f "h4 ,if      
possible1 ev]yone :o visits ! p>k %\ld  
take ?is %ort walk4 ,!  granite is      
well-expos$ at ! summit & dikes ( aplite
 & pegmatite  may be se54    ,! m       
v5turesome p>k visitor w want to make   
o!r trips away  f ! 8beat5 pa?0 into !  
wild]ness ( ! ,v]mont woods4 ,!         
pr9cipal difficulty arises 9 t !        
wild]ness is s real a p]son  may well   
become lo/ if he /rays too f> f !       
trails4 ,"s ( !  trails h become ov]gr[n
 s t !y are difficult to foll[ &        
portions ( o!rs h be5 de/roy$ by ! damm+
 up ( brooks by  ! beav]s4 ,x is sugge/$

 t 9 plann+ hikes in=mation be  obta9$ f
 ! p>k sup]9t5d5t ab\t ! condition ( !  
v>i\s  trails4        ,illu/ration3     
,figure #f4 ,diagrammatic sket* %[+ !   
relations      betwe5 ! s*i/ ( ! ,waits 
,riv] =mation & ! granite on      ! ea/ 
side ( ! railroad cut1 at ,rick] ,mills4
      ,,granite    ,,waits ,,riv]       
,,=mation    ,an int]e/+ hike c be made 
f ,osmore ,pond to ,de] ,m\nta9 b z  !  
trail is poorly m>k$1 "o mu/ ma9ta9 a   
s5se ( direction4 ,f  ! ,osmore picnic  
area walk s\? ne> ! %ore ( ! pond to its
  outlet into ,osmore ,brook4 ,at ?is   
po9t turn left to ! nor!a/ &  foll[ !   
trail :i* p>allels a wire m>k+ ! edge ( 
! game  pres]ve4 ,ab\t ?ree-f\r?s ( a   
mile f ,osmore ,brook ! trail  meets    
ano!r trail at "r angles4 ,to ! left !  
trail foll[s !  game pres]ve b\nd>y     
nor?we/w>d4 ,! trail to ! "r leads      
directly to ! top ( ,de] ,m\nta9 :]e a  
view may be obta9$ on !  s\? side ( !   
summit4 ,z an alt]nate r\te = return+1  
foll[  ! trail along ! game pres]ve to !

 nor?we/4 ,"s di/ance beyond  a         
%elt]-lean-to ! trail divides sev]al    
times ) ! ma9 trail  lead+ to ,blake    
,hill & o!r trails to ! left lead+ to ! 
,osmore  ,pond road4    ,a hike along ! 
trail on ! nor? side ( ,kettle ,pond to 
!  %elt]-lean-tos makes a pleasant trip 
along ! wat]4 ,also1 ! trail  f ,owl%ead
 ,m\nta9 to ,osmore ,pond is conv5i5t = 
a %ort hike  ?r\gh ! woods1 if ! trail c
 be f\nd4      ,qu>ries at ,ea/ ,b>re   
,! granite qu>ries at ,ea/ ,b>re are 9  
ne>ly ! same type ( rock  z t :i* occurs
 at ,groton ,/ate ,=e/4 ,! qu>ry        
op]ations are  int]e/+ & educational & !
 qu>ries af=d a good opportunity  ( see+
 fre%1 unalt]$ specim5s ( granite4      
,guide s]vice is  (f]$ at "s ( !        
qu>ries4                                
,,footnotes      #a;,granite is a type (
 igne\s rock consi/+ ( l>ge int]lock+   
gra9s ( light-color$ m9]als4 ,rocks are 
classifi$ z be+      ei!r igne\s1       
s$im5t>y1 or metamorphic4 ,igne\s rocks 
=m by      ! solidification ( molt5     

mat]ial2 s$im5t>y rocks =m by      !    
accumulation ( s$im5ts d]iv$ f old]     
rocks2 &      metamorphic rocks =m by ! 
recry/allization ( old] rocks      "u   
conditions ( high temp]atures &         
pressures4    #b;,dip is ! incl9ation ( 
a surface z1 = example1 a jo9t          
surface describ$ above4    #c,s*i/ is ! 
"n giv5 to rocks 9 :i* ! m9]als h a     
p>allel alignm5t due to reorganization (
 ! rock con/itu5ts      dur+ a condition
 ( high temp]ature & pressure4 ,! platy 
m9]als1 l mica1 =m at "r angles to !    
pressure s t      ! result+ rock may h a
 8b$d$0 appe>ance4                      
,illu/ration3 ,look+ nor?we/ ov] ,groton
 ,pond t[>d ,owl%ead      ,m\nta9       
,illu/ration3 ,look+ nor? ov] ,groton   
,pond t[>d ,little ,de]      ,m\nta9    
,transcrib]'s ,notes      --,sil5tly    
correct$ a few typos4    --,reta9$      
publication in=mation f ! pr9t$ edition3
 ?is e,book    is public-doma9 9 !      
c\ntry ( publication4    --,9 ! text    
v]sions only1 text 9 italics is delimit$

 by    und]scores4