﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  89 
  

  

  north 
  Atlantic 
  coast 
  line 
  was 
  then 
  considerably 
  farther 
  out 
  than 
  

   now 
  because 
  of 
  the 
  greater 
  elevation 
  of 
  the 
  land. 
  

  

  Direction 
  of 
  movement 
  and 
  depth 
  of 
  ice 
  in 
  New 
  York. 
  The 
  fact 
  

   that 
  glacial 
  ice 
  flows 
  as 
  though 
  it 
  were 
  a 
  viscous 
  substance 
  is 
  well 
  

   known 
  from 
  studies 
  of 
  present-day 
  glaciers 
  in 
  the 
  Alps, 
  Alaska, 
  

   or 
  the 
  Greenland 
  ice 
  sheet. 
  A 
  common 
  assumption, 
  either 
  that 
  the 
  

   land 
  at 
  the 
  center 
  of 
  accumulation 
  must 
  have 
  been 
  thousands 
  of 
  

   feet 
  higher 
  or 
  that 
  the 
  ice 
  there 
  must 
  have 
  been 
  immensely 
  thick, 
  

   in 
  order 
  to 
  permit 
  flowage 
  so 
  far 
  out 
  from 
  the 
  center, 
  is 
  not 
  neces- 
  

   sary. 
  For 
  instance, 
  if 
  one 
  proceeds 
  to 
  pour 
  viscous 
  tar 
  slowly 
  in 
  

   one 
  place 
  upon 
  a 
  perfectly 
  smooth 
  (level) 
  surface, 
  the 
  substance 
  

   will 
  gradually 
  flow 
  out 
  in 
  all 
  directions, 
  and 
  at 
  no 
  time 
  will 
  the 
  

   tar 
  at 
  the 
  center 
  of 
  accumulation 
  be 
  very 
  much 
  thicker 
  than 
  at 
  

   other 
  places. 
  The 
  movement 
  of 
  the 
  ice 
  from 
  one 
  of 
  the 
  great 
  

   centers 
  was 
  much 
  like 
  this, 
  only 
  in 
  the 
  case 
  of 
  the 
  glacier 
  the 
  

   accumulation 
  of 
  snow 
  and 
  ice 
  was 
  by 
  no 
  means 
  confined 
  to 
  the 
  

   immediate 
  centers 
  of 
  accumulation. 
  

  

  When 
  the 
  Labradorean 
  ice 
  sheet 
  spread 
  out 
  southward 
  as 
  far 
  as 
  

   northern 
  New 
  York, 
  the 
  Adirondack 
  mountains 
  stood 
  out 
  as 
  a 
  con- 
  

   siderable 
  obstacle 
  in 
  the 
  path 
  of 
  the 
  moving 
  ice, 
  and 
  the 
  tendency 
  

   was 
  for 
  the 
  current 
  to 
  divide 
  into 
  two 
  portions, 
  one 
  of 
  which 
  passed 
  

   southwestward 
  up 
  the 
  low, 
  broad 
  St 
  Lawrence 
  valley, 
  and 
  the 
  other 
  

   due 
  southward 
  through 
  the 
  deep, 
  narrow 
  Champlain 
  valley. 
  As 
  the 
  

   ice 
  kept 
  crowding 
  from 
  the 
  rear, 
  part 
  of 
  the 
  St 
  Lawrence 
  ice 
  lobe 
  

   pushed 
  into 
  the 
  Ontario 
  basin, 
  while 
  another 
  portion 
  pushed 
  its 
  

   way 
  up 
  the 
  broad, 
  low 
  Black 
  river 
  valley 
  and 
  finally 
  into 
  the 
  Mo- 
  

   hawk 
  valley. 
  At 
  the 
  same 
  time 
  the 
  Champlain 
  ice 
  lobe 
  found 
  its 
  

   way 
  into 
  the 
  upper 
  Hudson 
  valley, 
  and 
  sent 
  a 
  branch 
  lobe 
  up 
  the 
  

   broad, 
  low 
  Mohawk 
  valley. 
  The 
  two 
  Mohawk 
  lobes, 
  the 
  one 
  from 
  

   the 
  west 
  and 
  the 
  other 
  from 
  the 
  east, 
  met 
  in 
  the 
  Mohawk 
  valley 
  

   not 
  far 
  from 
  Little 
  Falls. 
  As 
  the 
  ice 
  sheet 
  continued 
  to 
  push 
  

   southward, 
  all 
  the 
  lowlands 
  of 
  northern 
  New 
  York 
  were 
  filled, 
  a 
  

   tongue 
  or 
  lobe 
  was 
  sent 
  down 
  the 
  Hudson 
  valley, 
  and 
  finally 
  the 
  

   whole 
  State, 
  except 
  the 
  southern 
  border 
  of 
  Long 
  Island, 
  was 
  buried 
  

   under 
  the 
  ice. 
  The 
  general 
  direction 
  of 
  ice 
  movement 
  at 
  this 
  time 
  

   of 
  greatest 
  ice 
  extent 
  was 
  southward 
  to 
  southwestward 
  with 
  per- 
  

   haps 
  some 
  undercurrents 
  determined 
  by 
  the 
  larger 
  topographic 
  

   features. 
  Thus 
  we 
  learn 
  that 
  the 
  major 
  relief 
  features 
  of 
  the 
  State 
  

   very 
  largely 
  determined 
  the 
  direction 
  of 
  ice 
  currents, 
  except 
  at 
  the 
  

   time 
  of 
  maximum 
  glaciation 
  when 
  only 
  the 
  undercurrents 
  were 
  

   controlled. 
  

  

  These 
  ideas 
  are 
  abundantly 
  borne 
  out 
  by 
  the 
  character 
  and 
  dis- 
  

   tribution 
  of 
  the 
  glacial 
  striae 
  and 
  boulders 
  over 
  the 
  State. 
  Central 
  

  

  