﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  93 
  

  

  In 
  conclusion 
  we 
  may 
  say 
  that 
  while 
  many 
  comparatively 
  small, 
  

   local 
  features 
  were 
  produced 
  by 
  ice 
  erosion, 
  the 
  major 
  topographic 
  

   features 
  of 
  the 
  State 
  were 
  practically 
  unaffected 
  by 
  ice 
  erosion 
  

   due 
  to 
  the 
  passage 
  of 
  the 
  great 
  ice 
  sheet. 
  

  

  Ice 
  deposits. 
  The 
  vast 
  amount 
  of 
  debris 
  transported 
  by 
  the 
  great 
  

   ice 
  sheet 
  was 
  carried 
  either 
  on 
  its 
  surface, 
  or 
  frozen 
  within 
  it, 
  or 
  

   pushed 
  along 
  under 
  it. 
  It 
  was 
  very 
  heterogeneous 
  material 
  ranging 
  

   from 
  the 
  finest 
  clay 
  through 
  sand 
  and 
  gravel, 
  to 
  boulders 
  of 
  many 
  

   tons 
  weight. 
  The 
  deposition 
  of 
  these 
  materials, 
  as 
  we 
  now 
  see 
  

   them, 
  took 
  place 
  during 
  both 
  the 
  advance 
  and 
  retreat 
  of 
  the 
  ice, 
  but 
  

   chiefly 
  during 
  its 
  retreat. 
  Most 
  of 
  the 
  deposits 
  made 
  during 
  the 
  

   ice 
  advance 
  were 
  obliterated 
  by 
  ice 
  erosion, 
  while 
  those 
  formed 
  

   during 
  the 
  ice 
  retreat 
  have 
  been 
  left 
  intact 
  except 
  for 
  the 
  small 
  

   amount 
  of 
  postglacial 
  erosion. 
  The 
  general 
  term 
  applied 
  to 
  all 
  

   deposits 
  of 
  glacial 
  origin 
  is 
  " 
  drift," 
  this 
  term 
  having 
  been 
  given 
  

   at 
  the 
  time 
  when 
  they 
  were 
  regarded 
  as 
  flood 
  deposits. 
  Drift 
  

   deposits 
  cover 
  practically 
  all 
  of 
  New 
  York 
  State 
  except 
  where 
  bare 
  

   rock 
  is 
  actually 
  exposed, 
  and 
  its 
  thickness 
  is 
  very 
  variable, 
  ranging 
  

   from 
  nothing 
  to 
  several 
  hundred 
  feet. 
  

  

  The 
  ice 
  sheet 
  could 
  advance 
  only 
  when 
  the 
  rate 
  of 
  motion 
  was 
  

   greater 
  than 
  the 
  rate 
  of 
  melting 
  of 
  the 
  ice 
  front 
  and 
  vice 
  versa 
  in 
  

   the 
  case 
  of 
  retreat. 
  Thus 
  it 
  is 
  true, 
  though 
  seemingly 
  paradoxical, 
  

   to 
  assert 
  that 
  the 
  ice 
  was 
  constantly 
  flowing 
  southward 
  even 
  while 
  

   the 
  ice 
  front 
  was 
  retreating 
  northward. 
  Whenever, 
  during 
  the 
  

   great 
  general 
  retreat, 
  the 
  ice 
  front 
  remained 
  stationary 
  because 
  the 
  

   forward 
  motion 
  of 
  the 
  ice 
  was 
  just 
  counterbalanced 
  by 
  the 
  melting, 
  

   all 
  the 
  ice 
  reaching 
  the 
  margin 
  of 
  the 
  glacier 
  dropped 
  its 
  load 
  to 
  

   build 
  up 
  a 
  terminal 
  moraine. 
  Such 
  a 
  moraine 
  is 
  a 
  more 
  or 
  less 
  

   distinct 
  range 
  of 
  low 
  hills 
  and 
  depressions 
  consisting 
  of 
  very 
  

   heterogeneous 
  and 
  generally 
  unstratified 
  debris, 
  though 
  at 
  times 
  

   waters 
  emerging 
  from 
  the 
  ice 
  caused 
  stratification. 
  The 
  depres- 
  

   sions 
  are 
  usually 
  called 
  kettle 
  holes. 
  The 
  so-called 
  great 
  terminal 
  

   moraine 
  marks 
  the 
  southernmost 
  limit 
  of 
  the 
  ice 
  sheet, 
  and 
  is 
  

   wonderfully 
  well 
  shown 
  by 
  the 
  ridge 
  o-f 
  low 
  irregular 
  hills 
  extend- 
  

   ing 
  the 
  whole 
  length 
  of 
  Long 
  Island 
  (see 
  plate 
  12). 
  It 
  is 
  also 
  

   clearly 
  traceable 
  across 
  northern 
  New 
  Jersey 
  and 
  Pennsylvania 
  and 
  

   passes 
  through 
  southern 
  Cattaraugus 
  county 
  in 
  New 
  York. 
  

   Terminal 
  moraines 
  farther 
  northward 
  are 
  generally 
  not 
  so 
  long 
  

   nor 
  sharply 
  defined, 
  the 
  one 
  of 
  perhaps 
  most 
  prominence 
  having 
  

   been 
  traced 
  from 
  Herkimer 
  through 
  Oriskany 
  Falls, 
  Cortland, 
  

   Watkins, 
  Bath, 
  Portageville, 
  Dayton, 
  and 
  Jamestown. 
  Moraines, 
  

   either 
  terminal 
  or 
  lateral, 
  are 
  often 
  locally 
  very 
  prominently 
  

   developed. 
  

  

  