﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  19 
  

  

  escarpment, 
  standing 
  out 
  abruptly 
  and 
  to 
  a 
  great 
  height, 
  forms 
  a 
  

   sharp 
  boundary. 
  On 
  the 
  eastern 
  side 
  the 
  Catskills 
  present 
  a 
  very 
  

   steep, 
  high 
  front 
  facing 
  the 
  Hudson 
  valley. 
  This 
  steep 
  front 
  rises 
  

   about 
  3000 
  feet 
  and 
  consists 
  of 
  hard 
  Devonic 
  sandstones 
  and 
  con- 
  

   glomerates 
  overlying 
  the 
  Siluric 
  strata 
  (see 
  figure 
  6). 
  

  

  MOHAWK 
  VALLEY 
  PROVINCE 
  

  

  The 
  Mohawk 
  valley 
  province, 
  though 
  comparatively 
  small, 
  is 
  of 
  

   great 
  importance 
  because 
  it 
  so 
  clearly 
  separates 
  the 
  Adirondack 
  

   highlands 
  on 
  the 
  north 
  from 
  the 
  highlands 
  of 
  the 
  Catskills 
  and 
  

   southwestern 
  plateau 
  provinces 
  on 
  the 
  south. 
  In 
  fact 
  it 
  should 
  be 
  

   noted 
  that 
  the 
  Mohawk 
  valley 
  is 
  by 
  far 
  the 
  lowest 
  passageway 
  across 
  

   the 
  mountains 
  between 
  the 
  St 
  Lawrence 
  river 
  and 
  the 
  southern 
  end 
  

   of 
  the 
  Appalachian 
  range. 
  This 
  low 
  pass 
  is 
  one 
  of 
  the 
  great 
  eastern 
  

   " 
  gateways 
  " 
  which, 
  with 
  the 
  St 
  Lawrence, 
  have 
  afforded 
  the 
  easiest 
  

   means 
  of 
  communication 
  between 
  the 
  Atlantic 
  seaboard 
  and 
  the 
  

   region 
  west 
  of 
  the 
  Appalachian 
  mountains. 
  

  

  The 
  comparatively 
  narrow 
  inner 
  valley 
  through 
  which 
  the 
  river 
  

   now 
  flows 
  is 
  often 
  erroneously 
  called 
  the 
  Mohawk 
  valley, 
  but 
  in 
  

   reality 
  the 
  whole 
  depression, 
  from 
  10 
  to 
  30 
  miles 
  wide 
  and 
  fully 
  

   1000 
  feet 
  deep, 
  between 
  the 
  northern 
  and 
  southern 
  highlands 
  of 
  

   the 
  State, 
  should 
  be 
  called 
  the 
  Mohawk 
  valley. 
  At 
  Little 
  Falls 
  the 
  

   inner 
  valley 
  narrows 
  to 
  a 
  gorge 
  several 
  hundred 
  feet 
  deep, 
  where 
  

   the 
  river 
  has 
  cut 
  its 
  way 
  through 
  a 
  preglacial 
  divide 
  (see 
  plate 
  7 
  

   and 
  figure 
  7). 
  Had 
  it 
  not 
  been 
  for 
  the 
  recent 
  cutting 
  of 
  this 
  gorge 
  

   (see 
  explanation 
  accompanying 
  plate 
  44 
  in 
  chapter 
  6) 
  through 
  the 
  

   barrier 
  at 
  Little 
  Falls, 
  the 
  Mohawk 
  valley 
  would 
  never 
  have 
  been 
  so 
  

   important 
  as 
  a 
  great 
  gateway 
  between 
  the 
  Atlantic 
  coast 
  and 
  the 
  west. 
  

   Today 
  the 
  four 
  tracks 
  of 
  the 
  New 
  York 
  Central 
  Railroad, 
  two 
  tracks 
  

   of 
  the 
  West 
  Shore 
  Railroad, 
  the 
  Erie 
  canal 
  (now 
  being 
  enlarged 
  to 
  

   the 
  Barge 
  canal), 
  an 
  important 
  highway, 
  many 
  telegraph 
  and 
  tele- 
  

   phone 
  wires, 
  and 
  the 
  Mohawk 
  river 
  all 
  pass 
  through 
  this 
  narrow 
  

   gorge 
  and 
  within 
  a 
  few 
  hundred 
  feet 
  of 
  sea 
  level. 
  Eastward 
  and 
  

   westward 
  from 
  Little 
  Falls, 
  the 
  inner 
  valley 
  is 
  generally 
  fairly 
  wide 
  

   and 
  open 
  (see 
  plate 
  7). 
  At 
  Little 
  Falls 
  the 
  Mohawk 
  river 
  is 
  less 
  

   than 
  400 
  feet 
  above 
  sea 
  level 
  and 
  even 
  at 
  Rome, 
  in 
  the 
  western 
  

   part 
  of 
  the 
  province, 
  the 
  river 
  shows 
  an 
  altitude 
  of 
  only 
  420 
  feet. 
  

  

  The 
  principal 
  rocks 
  of 
  the 
  province 
  are 
  shales, 
  sandstones 
  and 
  

   limestones 
  of 
  Cambric 
  and 
  Ordovicic 
  ages 
  ; 
  of 
  these 
  the 
  soft, 
  black 
  

   shales 
  of 
  Trenton, 
  Utica, 
  and 
  Frankfort 
  ages 
  are 
  in 
  greatest 
  

   abundance. 
  The 
  valley 
  owes 
  its 
  existence 
  largely 
  to 
  the 
  presence 
  

   of 
  this 
  belt 
  of 
  soft 
  shales 
  lying 
  between 
  -the 
  hard 
  crystalline 
  rocks 
  

  

  