﻿-±10 
  J. 
  Bar 
  veil 
  — 
  The 
  Piedmont 
  Terraces 
  

  

  floor 
  dips 
  more 
  steeply 
  than 
  the 
  grade 
  of 
  the 
  streams 
  and 
  

   gives 
  rise 
  to 
  rapids. 
  When 
  the 
  land 
  stood 
  lower 
  the 
  

   Coastal 
  Plain 
  extended 
  farther 
  westward 
  and 
  the 
  fall 
  

   line 
  lay 
  west 
  of 
  its 
  present 
  position. 
  It 
  has 
  existed 
  only 
  

   during 
  the 
  youthful 
  stages 
  of 
  the 
  river 
  grades. 
  As 
  the 
  

   streams 
  have 
  sunk 
  to 
  baselevel 
  after 
  each 
  uplift 
  the 
  fall 
  

   line 
  has 
  disappeared. 
  There 
  is 
  no 
  evidence, 
  as 
  was 
  once 
  

   thought, 
  that 
  the 
  fall 
  line 
  marks 
  a 
  fault 
  which 
  has 
  sep- 
  

   arated 
  the 
  Piedmont 
  Plateau 
  from 
  the 
  Coastal 
  Plain. 
  

   On 
  the 
  contrary, 
  no 
  such 
  fault 
  is 
  needed 
  to 
  explain 
  the 
  

   existence 
  of 
  the 
  fall 
  line 
  ; 
  indeed, 
  the 
  manner 
  in 
  which 
  

   the 
  Coastal 
  Plain 
  deposits 
  extend 
  for 
  many 
  miles 
  west- 
  

   ward 
  up 
  the 
  interfluvial 
  slopes 
  shows 
  that 
  such 
  a 
  fault 
  

   does 
  not 
  exist. 
  

  

  Only 
  during 
  the 
  most 
  widely 
  submergent 
  phases 
  of 
  

   crustal 
  oscillations 
  has 
  marine 
  planation 
  acted 
  on 
  the 
  

   surface 
  of 
  the 
  Piedmont 
  Plateau. 
  Through 
  by 
  far 
  the 
  

   greater 
  part 
  of 
  later 
  geologic 
  time 
  fluvial 
  denudation 
  has 
  

   been 
  acting 
  and 
  destroying 
  such 
  marks 
  as 
  the 
  sea 
  left. 
  

   Evidence 
  of 
  marine 
  planation 
  must 
  be 
  sought, 
  therefore, 
  

   through 
  the 
  mask 
  of 
  later 
  cycles 
  of 
  fluvial 
  erosion. 
  The 
  

   older 
  traces 
  can 
  only 
  remain 
  on 
  the 
  hard 
  rocks 
  where 
  

   these 
  were 
  favorably 
  exposed 
  to 
  the 
  attack 
  of 
  the 
  sea 
  but 
  

   have 
  been 
  protected, 
  in 
  a 
  measure, 
  from 
  later 
  fluvial 
  

   denudation. 
  The 
  protected 
  situations 
  are 
  interfluvial 
  

   ridges 
  on 
  hard 
  formations 
  which 
  were 
  subjected 
  to 
  

   marine 
  planation 
  and 
  which 
  are 
  remote 
  from 
  the 
  prin- 
  

   cipal 
  drainage 
  channels. 
  

  

  It 
  would 
  thus 
  appear 
  that 
  a 
  particular 
  phase 
  of 
  marine 
  

   planation 
  is 
  apt 
  to 
  be 
  developed 
  on 
  a 
  particular 
  geologic 
  

   formation. 
  But 
  on 
  a 
  single 
  formation 
  it 
  will 
  be 
  difficult 
  

   to 
  tell 
  if 
  the 
  original 
  erosion 
  forms 
  are 
  due 
  to 
  fluvial 
  or 
  

   marine 
  action, 
  especially 
  after 
  further 
  erosion 
  in 
  later 
  

   cycles. 
  The 
  evidence 
  will 
  be 
  clearest 
  where 
  an 
  old 
  

   shore-line 
  crosses 
  a 
  single 
  geologic 
  formation 
  of 
  uniform 
  

   hardness 
  one 
  part 
  of 
  which 
  shows 
  higher 
  levels 
  and 
  one 
  

   character 
  of 
  topography 
  and 
  drainage 
  as 
  contrasted 
  with 
  

   another 
  lower 
  part. 
  In 
  particular, 
  southern 
  New 
  Eng- 
  

   land 
  is 
  adapted 
  to 
  show 
  these 
  relations 
  most 
  convinc- 
  

   ingly. 
  

  

  Enduring 
  distinctions 
  between 
  fluvial 
  and 
  marine 
  erosion. 
  

  

  "We 
  have 
  seen 
  that 
  streams, 
  even 
  those 
  of 
  moderate 
  

   size, 
  are 
  well 
  able 
  to 
  cut 
  their 
  channels 
  quickly 
  down 
  to 
  

  

  