﻿358 
  

  

  J. 
  Barrel! 
  — 
  The 
  Piedmont 
  Terraces 
  

  

  to 
  CO 
  at 
  T' 
  and 
  to 
  BN 
  midway 
  between 
  T 
  and 
  T'. 
  Then 
  

   when 
  the 
  strand-line 
  is 
  at 
  C, 
  for 
  example, 
  there 
  will 
  be 
  

   erosion 
  on 
  the 
  landward 
  side 
  from 
  T', 
  whereas 
  offshore 
  

   from 
  that 
  point 
  there 
  will 
  be 
  aggradation. 
  

  

  In 
  long 
  continued 
  planation 
  this 
  offshore 
  aggradation 
  

   very 
  greatly 
  reduces 
  the 
  work 
  of 
  the 
  sea 
  in 
  cutting 
  inland, 
  

   for 
  the 
  depth 
  of 
  bottom 
  erosion 
  is 
  reduced 
  from 
  AX, 
  the 
  

   ultimate 
  depth 
  of 
  effective 
  wave 
  action, 
  to 
  AT'. 
  For 
  

   example, 
  take 
  the 
  profile 
  given 
  in 
  the 
  preceding 
  topic 
  for 
  

   a 
  stormy 
  shelf 
  sea. 
  If 
  submergence 
  to 
  a 
  depth 
  of 
  three 
  

   fathoms 
  should 
  go 
  forward 
  while 
  the 
  sea 
  were 
  cutting 
  

  

  Pig. 
  17. 
  

  

  Coast 
  

  

  fn/f/al 
  sea 
  /et/e/. 
  

  

  Fig. 
  17. 
  — 
  Successive 
  stages 
  of 
  marine 
  erosion 
  on 
  a 
  sinking 
  coast. 
  

  

  inland 
  one 
  mile, 
  the 
  slope 
  would 
  be 
  tangent 
  to 
  the 
  profile 
  

   of 
  equilibrium 
  two 
  miles 
  from 
  the 
  shore 
  at 
  a 
  depth 
  of 
  

   eleven 
  fathoms. 
  To 
  maintain 
  this 
  profile 
  marine 
  denu- 
  

   dation 
  would 
  need 
  to 
  go 
  forward 
  to 
  a 
  depth 
  of 
  only 
  eleven 
  

   fathoms 
  instead 
  of 
  an 
  ultimate 
  depth 
  of 
  about 
  fifty, 
  as 
  in 
  

   the 
  case 
  of 
  a 
  static 
  sea-level. 
  Thus 
  the 
  work 
  of 
  marine 
  

   denudation 
  would 
  be 
  reduced 
  about 
  four-fifths. 
  A 
  very 
  

   slight 
  rate 
  of 
  submergence, 
  therefore, 
  will 
  bring 
  about 
  a 
  

   retreat 
  of 
  the 
  shore 
  inland 
  several 
  times 
  faster 
  than 
  

   under 
  stationary 
  conditions 
  of 
  land 
  and 
  sea. 
  

  

  Case 
  III. 
  The 
  more 
  usual 
  case 
  is 
  that 
  of 
  rapid 
  sub- 
  

   mergence 
  after 
  which 
  the 
  sea 
  cuts 
  inland 
  and 
  establishes 
  

   a 
  normal 
  profile. 
  This 
  condition 
  exists 
  at 
  present 
  in 
  

   many 
  regions. 
  The 
  best 
  studied 
  example 
  is 
  that 
  of 
  the 
  

  

  