﻿50 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Accompanying 
  the 
  Taconic 
  disturbance 
  and 
  possibly 
  aiding 
  the 
  

   metamorphism 
  were 
  minor 
  molten 
  rock 
  intrusions 
  in 
  the 
  form 
  of 
  

   dikes. 
  These 
  dikes 
  break 
  through 
  late 
  Ordovicic 
  strata 
  and 
  hence 
  

   can 
  not 
  be 
  older 
  than 
  late 
  Ordovicic. 
  A 
  fine 
  example 
  of 
  one 
  of 
  

   these 
  dikes 
  on 
  Manhattan 
  island 
  is 
  shown 
  in 
  plate 
  24. 
  

  

  The 
  great 
  compressive 
  force 
  which 
  folded 
  and 
  upraised 
  the 
  

   Taconic 
  mountains 
  did 
  not 
  accomplish 
  its 
  work 
  suddenly. 
  The 
  

   force 
  was 
  slowly 
  and 
  irresistibly 
  applied 
  and 
  the 
  mass 
  of 
  strata 
  

   was 
  gradually 
  bulged 
  and 
  bent, 
  or 
  fractured 
  if 
  near 
  the 
  surface, 
  the 
  

   amount 
  of 
  time 
  required 
  for 
  the 
  whole 
  operation 
  being 
  perhaps 
  

   very 
  long 
  but 
  beyond 
  estimate. 
  Such 
  a 
  length 
  of 
  time 
  is, 
  however, 
  

   so 
  short 
  compared 
  with 
  all 
  known 
  geologic 
  history 
  that 
  we 
  are 
  

   accustomed 
  to 
  refer 
  to 
  the 
  formation 
  of 
  such 
  a 
  mountain 
  range 
  as 
  

   simply 
  an 
  event 
  of 
  earth 
  history. 
  

  

  From 
  these 
  statements 
  we 
  see 
  that, 
  even 
  before 
  the 
  range 
  had 
  

   attained 
  its 
  maximum 
  height 
  above 
  sea 
  level, 
  a 
  very 
  considerable 
  

   amount 
  of 
  erosion 
  must 
  have 
  taken 
  place. 
  When 
  the 
  very 
  first 
  

   fold 
  appeared 
  above 
  the 
  ocean 
  level, 
  erosion 
  began 
  its 
  work 
  and 
  

   continued 
  with 
  increasing 
  vigor 
  as 
  the 
  mountain 
  masses 
  got 
  higher 
  

   and 
  higher. 
  Thus 
  we 
  have 
  the 
  warfare 
  between 
  two 
  great 
  natural 
  

   processes 
  — 
  the 
  building 
  up 
  and 
  the 
  tearing 
  down. 
  So 
  long 
  as 
  the 
  

   building 
  up 
  process 
  predominated, 
  the 
  mountain 
  range 
  increased 
  in 
  

   elevation, 
  and 
  we 
  say 
  the 
  range 
  was 
  in 
  its 
  period 
  of 
  youth. 
  When 
  

   the 
  opposing 
  forces 
  were 
  about 
  equally 
  balanced, 
  the 
  range 
  tended 
  

   to 
  remain 
  at 
  a 
  constant 
  elevation 
  and 
  we 
  say 
  the 
  mountains 
  were 
  

   in 
  the 
  period 
  of 
  maturity. 
  When 
  the 
  tearing 
  down 
  (erosive) 
  

   process 
  was 
  predominant, 
  we 
  speak 
  of 
  the 
  range 
  as 
  having 
  been 
  in 
  

   old 
  age. 
  When 
  the 
  mountains 
  have 
  been 
  completely 
  worn 
  down 
  

   close 
  to 
  sea 
  level 
  (peneplain) 
  we 
  speak 
  of 
  the 
  death 
  of 
  the 
  range. 
  

   Here 
  is 
  an 
  example 
  of 
  one 
  of 
  the 
  remarkable 
  procedures 
  of 
  

   nature. 
  After 
  millions 
  of 
  years 
  of 
  work 
  by 
  the 
  deposition 
  of 
  

   thousands 
  of 
  feet 
  of 
  strata, 
  layer 
  upon 
  layer 
  on 
  an 
  ocean 
  bottom, 
  

   a 
  great 
  compressive 
  force 
  is 
  brought 
  to 
  bear 
  and 
  a 
  magnificent 
  

   mountain 
  range 
  is 
  literally 
  born 
  out 
  of 
  the 
  ocean. 
  No 
  sooner 
  is 
  

   this 
  great 
  mountain 
  range 
  well 
  formed 
  than 
  the 
  destructive 
  

   processes 
  unceasingly 
  destroy 
  this 
  marvelous 
  work. 
  But 
  the 
  sedi- 
  

   ments 
  derived 
  from 
  the 
  wear 
  of 
  this 
  range 
  are 
  carried 
  into 
  the 
  

   nearest 
  ocean 
  again 
  to 
  accumulate 
  and 
  after 
  long 
  ages 
  to 
  be 
  raised 
  

   up 
  into 
  another 
  range; 
  and 
  so 
  the 
  process 
  is 
  often 
  repeated. 
  From 
  

   this 
  . 
  we 
  learn 
  that 
  the 
  mountain 
  ranges 
  of 
  the 
  earth 
  are 
  by 
  no 
  

   means 
  all 
  of 
  the 
  same 
  ag'e. 
  The 
  Adirondacks 
  are 
  older 
  than 
  the 
  

   Taconics, 
  and 
  these 
  older 
  than 
  the 
  Appalachians 
  ; 
  the 
  latter, 
  in 
  turn, 
  

  

  