﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  7 
  

  

  The 
  area 
  is 
  one 
  of 
  low 
  altitude 
  and 
  comparatively 
  little 
  relief, 
  

   forming 
  the 
  west 
  end 
  of 
  the 
  plain 
  which 
  borders 
  the 
  entire 
  north 
  

   front 
  of 
  the 
  Adirondack 
  highland, 
  and 
  merges 
  hereabouts 
  into 
  

   the 
  north 
  end 
  of 
  the 
  Black 
  river 
  lowland. 
  To 
  the 
  southward 
  

   the 
  altitude 
  considerably 
  increases 
  and 
  a 
  bit 
  of 
  the 
  high 
  Trenton 
  

   escarpment 
  which 
  forms 
  the 
  -west 
  wall 
  of 
  the 
  larger 
  part 
  of 
  the 
  

   valley 
  of 
  the 
  Black 
  river, 
  appears 
  in 
  the 
  extreme 
  southwest 
  

   corner 
  of 
  the 
  Theresa 
  sheet, 
  reaching 
  an 
  altitude 
  of 
  over 
  800 
  

   feet, 
  the.highest 
  elevation 
  in 
  the 
  mapped 
  district. 
  Altitudes 
  con- 
  

   siderably 
  in 
  excess 
  of 
  this 
  appear 
  not 
  far 
  to 
  the 
  southward 
  on 
  the 
  

   A¥atertown 
  sheet. 
  But 
  with 
  this 
  one 
  trifling 
  exception 
  the 
  high- 
  

   est 
  elevations 
  in 
  the 
  mapped 
  area 
  but 
  little 
  exceed 
  600 
  feet 
  

   (this 
  in 
  the 
  southeast 
  corner 
  of 
  the 
  Theresa 
  sheet) 
  and 
  thence 
  

   drop 
  gently 
  to 
  the 
  north 
  and 
  west 
  to 
  the 
  level 
  of 
  the 
  lake 
  and 
  

   river 
  (246 
  feet). 
  

  

  Though 
  the 
  district 
  is 
  thus 
  moderately 
  flat, 
  the 
  local 
  relief 
  is 
  

   considerable, 
  in 
  minor 
  fashion. 
  Ridges 
  and 
  valleys 
  characterize 
  

   the 
  districts 
  underlaid 
  by 
  Precambric 
  rocks. 
  The 
  flat-lying 
  

   Paleozoic 
  rocks 
  form 
  plains 
  which 
  are 
  fronted 
  by 
  steep 
  cliff 
  

   escarpments. 
  In 
  both 
  cases 
  abrupt 
  changes 
  of 
  level 
  of 
  from 
  50 
  

   to 
  100 
  feet 
  are 
  quite 
  common. 
  These 
  features 
  also 
  are 
  most 
  

   pronounced 
  in 
  the 
  eastern 
  part 
  of 
  the 
  area 
  and 
  fade 
  out 
  westward, 
  

   so 
  that 
  but 
  little 
  relief 
  is 
  manifested 
  on 
  the 
  Cape 
  Vincent 
  and 
  

   the 
  larger 
  part 
  of 
  the 
  Clayton 
  sheet. 
  

  

  With 
  the 
  exception 
  of 
  the 
  St 
  Lawrence, 
  the 
  Black 
  and 
  Indian 
  

   rivers 
  are 
  the 
  only 
  streams 
  of 
  respectable 
  size 
  within 
  the 
  mapped 
  

   area. 
  Most 
  of 
  the 
  streams 
  flow 
  in 
  narrow, 
  steep 
  walled 
  valleys, 
  

   and 
  no 
  deep, 
  broadly 
  opened 
  valleys 
  have 
  been 
  detected. 
  There 
  

   are 
  many 
  features 
  of 
  interest 
  in 
  the 
  minor 
  drainage 
  to 
  which 
  

   attention 
  will 
  be 
  directed 
  later 
  on. 
  The 
  group 
  of 
  lakes 
  of 
  an 
  

   unusual 
  type 
  forms 
  a 
  very 
  prominent 
  feature. 
  Several 
  of 
  these 
  

   lakes 
  may 
  be 
  noted 
  near 
  the 
  eastern 
  edge 
  of 
  the 
  Alexandria 
  sheet 
  

   and 
  there 
  are 
  a 
  few 
  more 
  beyond 
  the 
  map 
  limits. 
  They 
  are 
  not 
  

   a 
  usual 
  feature 
  of 
  this 
  part 
  of 
  the 
  State. 
  Their 
  presence 
  and 
  

   their 
  very 
  localized 
  distribution 
  require 
  explanation. 
  

  

  Glacial 
  deposits 
  are 
  in 
  small 
  bulk 
  in 
  the 
  district 
  and 
  much 
  bare 
  

   rock 
  -appears, 
  with 
  wide 
  areas 
  where 
  the 
  soil 
  is 
  very 
  thin. 
  In 
  

   the 
  limestone 
  districts 
  the 
  streams 
  show 
  a 
  tendency 
  to 
  go 
  under- 
  

   ground 
  and 
  bared 
  limestone 
  surfaces 
  show 
  considerable 
  amount 
  

   of 
  rock 
  removal 
  through 
  solution 
  along 
  the 
  joint 
  planes. 
  

  

  The 
  district 
  is 
  largely 
  one 
  of 
  small 
  farms. 
  Little 
  or 
  no 
  forest 
  

   remains 
  on 
  it, 
  though 
  there 
  is 
  much 
  waste 
  land. 
  The 
  largest 
  

  

  