﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  21 
  

  

  Falls 
  and 
  " 
  The 
  Noses 
  " 
  (Yosts), 
  the 
  river 
  has 
  cut 
  down 
  to 
  the 
  Pre- 
  

   cambric 
  (Adirondack) 
  rock. 
  In 
  general, 
  the 
  rock 
  formations 
  of 
  

   the 
  province 
  tilt 
  slightly 
  southwestward 
  and 
  show 
  folding 
  only 
  on 
  

   a 
  very 
  small 
  scale. 
  From 
  Little 
  Falls 
  eastward, 
  however, 
  the 
  strata 
  

   are 
  greatly 
  disturbed 
  by 
  numerous 
  nearly 
  north-south 
  faults 
  which 
  

   are 
  often 
  of 
  considerable 
  magnitude 
  (see 
  figure 
  25). 
  

  

  ERIE-ONTARIO 
  PLAINS 
  PROVINCE 
  

  

  On 
  the 
  extreme 
  western 
  side 
  of 
  the 
  State, 
  and 
  lying 
  between 
  

   Lake 
  Erie 
  and 
  the 
  Southwestern 
  plateau, 
  there 
  is 
  a 
  strip 
  of 
  land 
  

   only 
  a 
  few 
  miles 
  wide 
  which 
  may 
  be 
  called 
  the 
  Erie 
  plain. 
  This 
  

   plain 
  is 
  of 
  very 
  low 
  relief 
  and 
  slopes 
  from 
  an 
  altitude 
  of 
  from 
  

   800 
  to 
  900 
  feet 
  down 
  to 
  the 
  level 
  of 
  Lake 
  Erie, 
  whose 
  altitude 
  is 
  

   573 
  feet. 
  Where 
  the 
  Erie 
  plain 
  joins 
  the 
  Southwestern 
  plateau 
  

   there 
  is 
  a 
  very 
  decided 
  change 
  of 
  slope. 
  The 
  rocks 
  underlying 
  this 
  

   plain 
  are 
  dark 
  shales 
  of 
  Devonic 
  age 
  and 
  show 
  the 
  usual 
  slight 
  

   southwestward 
  tilt 
  (see 
  plate 
  31). 
  

  

  The 
  Ontario 
  plain 
  is 
  much 
  larger 
  and 
  lies 
  between 
  Lake 
  Ontario 
  

   and 
  the 
  Southwestern 
  plateau, 
  the 
  southern 
  boundary 
  being 
  marked 
  

   by 
  the 
  " 
  Helderberg 
  escarpment." 
  This 
  large 
  province 
  slopes 
  

   gradually 
  to 
  the 
  shores 
  of 
  Lake 
  Ontario 
  and 
  is 
  remarkably 
  free 
  

   from 
  relief 
  features 
  of 
  any 
  considerable 
  magnitude. 
  One 
  that 
  

   deserves 
  mention 
  is 
  the 
  presence 
  of 
  many 
  hundreds 
  of 
  low, 
  glacial 
  

   knoibs 
  (drumlins) 
  which 
  are 
  thickly 
  scattered 
  over 
  the 
  whole 
  plain 
  

   between 
  Rochester 
  and 
  Syracuse 
  (see 
  plate 
  42). 
  .Another 
  feature 
  

   which 
  serves 
  to 
  break 
  the 
  monotony 
  of 
  the 
  plain 
  on 
  the 
  west 
  is 
  the 
  

   low 
  but 
  distinct 
  escarpment 
  of 
  Niagara 
  limestone, 
  which 
  extends 
  

   from 
  Lewiston 
  eastward 
  to 
  beyond 
  Lockport. 
  On 
  the 
  east 
  the 
  

   Ontario 
  plain 
  gradually 
  merges 
  into 
  the 
  Mohawk 
  valley 
  province 
  

   on 
  the 
  one 
  hand, 
  and 
  on 
  the 
  other 
  hand 
  comes 
  against 
  the 
  western 
  

   foot 
  of 
  the 
  highlands 
  of 
  the 
  Tug 
  Hill 
  province. 
  

  

  The 
  rocks 
  underlying 
  the 
  Ontario 
  plain 
  are 
  chiefly 
  sandstones, 
  

   limestones 
  and 
  shales 
  of 
  Siluric 
  age, 
  which 
  show 
  the 
  usual 
  tilt 
  

   toward 
  the 
  south. 
  At 
  the 
  extreme 
  northeast, 
  limestone 
  and 
  shale 
  

   of 
  Ordovicic 
  age 
  are 
  present 
  and 
  these 
  show 
  a 
  slight 
  westward 
  tilt. 
  

  

  TUG 
  HILL 
  PROVINCE 
  

  

  The 
  Tug 
  Hill 
  region 
  is 
  worthy 
  of 
  recognition 
  as 
  a 
  distinct 
  physio- 
  

   graphic 
  province 
  because 
  we 
  have 
  here 
  a 
  highland 
  mass 
  of 
  con- 
  

   siderable 
  extent 
  entirely 
  separated 
  from 
  the 
  neighboring 
  provinces. 
  

   The 
  highest 
  point, 
  six 
  miles 
  west-northwest 
  of 
  Lyons 
  Falls, 
  Lewis 
  

  

  