﻿92 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  erosion 
  in 
  the 
  Black 
  river 
  valley, 
  and 
  figure 
  35 
  is 
  a 
  structure 
  sec- 
  

   tion 
  across 
  the 
  valley 
  showing 
  the 
  rock 
  terraces 
  and 
  the 
  relations 
  

   of 
  the 
  various 
  rock 
  formations. 
  The 
  high, 
  steep, 
  terrace 
  fronts 
  

   are 
  certainly 
  young 
  topographic 
  features 
  which 
  could 
  not 
  have 
  been 
  

   present 
  at 
  the 
  close 
  of 
  the 
  long 
  preglacial 
  erosion 
  period, 
  nor 
  could 
  

   they 
  have 
  been 
  formed 
  since 
  the 
  Ice 
  age 
  because 
  glacial 
  deposits, 
  

   even 
  near 
  the 
  valley 
  bottom, 
  have 
  not 
  yet 
  been 
  removed. 
  There 
  is 
  

   still 
  the 
  possibility 
  that 
  glacial 
  waters 
  may 
  have 
  done 
  the 
  work, 
  

   but 
  there 
  is 
  no 
  evidence 
  for 
  such 
  vigorous 
  water 
  action 
  especially 
  

   on 
  the 
  higher 
  part 
  of 
  the 
  Trenton 
  limestone 
  terrace 
  where 
  records 
  

   would 
  surely 
  be 
  left. 
  On 
  the 
  contrary, 
  there 
  are 
  glaciated 
  rock 
  

   surfaces 
  and 
  also 
  glacial 
  deposits 
  (kames) 
  on 
  the 
  great 
  limestone 
  

   terrace 
  and 
  near 
  the 
  base 
  of 
  the 
  steep 
  front 
  of 
  the 
  shale 
  terrace, 
  

   so 
  that 
  the 
  work 
  could 
  not 
  have 
  been 
  done 
  by 
  glacial 
  waters 
  before 
  

   the 
  ice 
  retreat. 
  Evidently, 
  we 
  have 
  here 
  a 
  fine 
  example 
  of 
  ice 
  

   erosion, 
  and 
  before 
  the 
  Ice 
  age 
  the 
  limestones 
  and 
  shales 
  extended 
  

   somewhat 
  farther 
  eastward 
  than 
  they 
  now 
  do. 
  The 
  conditions 
  for 
  

   ice 
  erosion 
  were 
  here 
  unusually 
  favorable 
  because 
  the 
  ice, 
  in 
  its 
  

   great 
  sweep 
  around 
  the 
  Adirondacks, 
  was 
  shod 
  with 
  many 
  frag- 
  

   ments 
  of 
  very 
  hard 
  rocks 
  and 
  entered 
  the 
  deep 
  Black 
  river 
  valley 
  

   striking 
  with 
  greatest 
  force 
  against 
  the 
  soft 
  sedimentary 
  rocks 
  of 
  

   the 
  west 
  side 
  of 
  the 
  valley. 
  As 
  the 
  figure 
  clearly 
  shows, 
  the 
  very 
  

   soft 
  shales 
  were 
  worn 
  back 
  more 
  than 
  the 
  harder 
  limestones, 
  while 
  

   the 
  very 
  hard 
  Precambric 
  rocks 
  were 
  very 
  little 
  affected. 
  This 
  is 
  

   perhaps 
  the 
  best 
  example 
  of 
  ice 
  erosion 
  in 
  northern 
  New 
  York, 
  and 
  

   even 
  here 
  we 
  must 
  admit 
  that 
  only 
  soft 
  rocks 
  were 
  much 
  eroded 
  

   and 
  that 
  the 
  great 
  preglacial 
  Black 
  river 
  valley 
  was 
  comparatively 
  

   little 
  modified. 
  If 
  soft 
  shales 
  had 
  made 
  up 
  the 
  valley 
  bottom, 
  ice 
  

   erosion 
  would 
  have 
  caused 
  considerable 
  deepening 
  as 
  was, 
  no 
  doubt, 
  

   the 
  case 
  in 
  the 
  valleys 
  of 
  the 
  Finger 
  lakes 
  region. 
  

  

  Most 
  of 
  the 
  Adirondack 
  mountain 
  peaks, 
  especially 
  the 
  more 
  

   isolated 
  ones, 
  were 
  thoroughly 
  scraped 
  off 
  and 
  rounded 
  down 
  to 
  

   the 
  very 
  live 
  or 
  fresh 
  rock 
  (see 
  upper 
  view, 
  plate 
  17), 
  while 
  the 
  

   favorably 
  situated 
  valleys 
  were 
  vigorously 
  glaciated 
  by 
  the 
  removal 
  

   of 
  all 
  the 
  rotten 
  and 
  at 
  least 
  some 
  of 
  the 
  fresh 
  rock, 
  especially 
  

   when 
  this 
  latter 
  was 
  the 
  comparatively 
  soft 
  Grenville 
  limestone. 
  

   Such 
  phenomena 
  are 
  particularly 
  well 
  exhibited 
  in 
  Warren 
  county 
  

   (see 
  figure 
  13) 
  where 
  the 
  landscape 
  is 
  characterized 
  by 
  many 
  great, 
  

   glaciated 
  rock 
  domes 
  which 
  rise 
  above 
  the 
  valleys 
  of 
  weak 
  Gren- 
  

   ville. 
  In 
  a 
  few 
  cases 
  where 
  the 
  ice 
  moved 
  directly 
  across 
  deep 
  

   valleys, 
  like 
  that 
  between 
  Lake 
  George 
  village 
  and 
  Warren 
  sburg, 
  

   the 
  rotten 
  rock 
  to 
  great 
  depth 
  may 
  still 
  be 
  seen 
  in 
  its 
  original 
  place. 
  

  

  