﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  2$ 
  

  

  and 
  into 
  Westchester 
  county. 
  The 
  relief 
  is 
  rather 
  rugged 
  with 
  the 
  

   higher 
  points 
  commonly 
  reaching 
  altitudes 
  of 
  over 
  1000 
  feet. 
  The 
  

   rocks 
  are 
  chiefly 
  granites 
  and 
  gneisses 
  of 
  Precambric 
  age, 
  and 
  are 
  

   in 
  most 
  ways 
  much 
  like 
  those 
  of 
  the 
  Adirondacks. 
  

  

  Region 
  north 
  of 
  the 
  Highlands. 
  North 
  of 
  the 
  Highlands 
  the 
  

   rocks 
  are 
  in 
  the 
  main 
  highly 
  metamorphosed 
  shales, 
  sandstones 
  and 
  

   limestones, 
  and 
  the 
  relief 
  is 
  generally 
  low 
  except 
  along 
  the 
  eastern 
  

   border 
  where 
  it 
  -is 
  almost 
  mountainous. 
  A 
  characteristic 
  feature 
  

   along 
  this 
  eastern 
  side 
  is 
  the 
  presence 
  of 
  long, 
  fairly 
  high, 
  nearly 
  

   north-south 
  ridges 
  separated 
  by 
  comparatively 
  narrow 
  valleys. 
  

  

  Shawangunk 
  mountain. 
  Lying 
  close 
  to 
  the 
  southeastern 
  border 
  

   of 
  the 
  Catskills 
  and 
  extending 
  northeastward 
  from 
  the 
  State 
  line 
  

   in 
  Orange 
  county 
  well 
  into 
  Ulster 
  county, 
  is 
  a 
  distinct 
  mountain 
  

   ridge 
  known 
  as 
  Shawangunk 
  mountain. 
  This 
  long, 
  narrow 
  moun- 
  

   tain 
  rises 
  iooo 
  feet 
  or 
  more 
  above 
  the 
  surrounding 
  country, 
  and 
  

   with 
  the 
  deep 
  narrow 
  Rondout 
  valley 
  immediately 
  on 
  its 
  west 
  side 
  

   and 
  the 
  broad, 
  open 
  Wallkill 
  valley 
  on 
  the 
  east, 
  it 
  is 
  truly 
  a 
  re- 
  

   markable 
  topographic 
  form. 
  The 
  capping 
  of 
  very 
  hard 
  Siluric 
  

   conglomerate 
  upon 
  the 
  soft 
  Ordovicic 
  shales 
  has 
  caused 
  the 
  ridge 
  

   to 
  stand 
  out 
  so 
  boldly 
  against 
  erosion 
  (see 
  figure 
  9 
  and 
  plate 
  28). 
  

  

  Region 
  south 
  of 
  the 
  Highlands. 
  Southern 
  Rockland 
  county 
  is 
  

   covered 
  by 
  Mesozoic 
  (Triassic) 
  sandstone. 
  This 
  rock 
  is 
  not 
  folded 
  

   but 
  contains 
  within 
  its 
  mass 
  great 
  sheets 
  of 
  lava 
  which 
  outcrop 
  to 
  

   form 
  the 
  Palisades 
  along 
  and 
  west 
  of 
  the 
  Hudson 
  (see 
  figure 
  20). 
  

  

  In 
  southern 
  Westchester 
  county 
  and 
  in 
  New 
  York 
  county 
  there 
  

   are 
  highly 
  folded 
  and 
  metamorphosed 
  Precambric 
  and 
  Ordovicic 
  

   rocks, 
  and 
  the 
  country 
  is 
  typically 
  hilly. 
  

  

  LONG 
  ISLAND 
  PROVINCE 
  

   This 
  province, 
  including 
  Staten 
  Island, 
  is 
  really 
  a 
  part 
  of 
  the 
  

   broad 
  Atlantic 
  coastal 
  plain 
  and 
  is 
  therefore 
  practically 
  devoid 
  of 
  

   any 
  hard 
  rock 
  formations 
  at 
  the 
  surface. 
  Except 
  for 
  a 
  few 
  ex- 
  

   posures 
  of 
  Cretacic 
  sands 
  and 
  gravels 
  along 
  the 
  northern 
  border, 
  

   the 
  whole 
  province 
  is 
  made 
  up 
  of 
  glacial 
  sands 
  and 
  gravels. 
  From 
  

   the 
  standpoint 
  of 
  surface 
  relief 
  the 
  province 
  is 
  clearly 
  divisible 
  into 
  

   two 
  parts, 
  a 
  northern 
  and 
  a 
  southern, 
  which 
  are 
  sharply 
  separated 
  

   from 
  each 
  other 
  (see 
  plate 
  12). 
  The 
  northern 
  part 
  is 
  character- 
  

   istically 
  hilly, 
  the 
  hills 
  being 
  of 
  glacial 
  (morainic) 
  origin. 
  The 
  

   maximum 
  elevation 
  is 
  less 
  than 
  400 
  feet, 
  while 
  in 
  general 
  the 
  hills 
  

   are 
  from 
  100 
  to 
  200 
  feet 
  high. 
  This 
  line 
  of 
  hills 
  ends 
  abruptly 
  

   about 
  midway 
  of 
  the 
  island 
  (north-south) 
  and 
  the 
  southern 
  part 
  of 
  

   the 
  province 
  is 
  a 
  sand 
  plain 
  of 
  remarkable 
  smoothness 
  with 
  a 
  gentle 
  

   slope 
  toward 
  the 
  ocean. 
  

  

  