THE  ELDERS  RIDGE  COAL  FIELD,  PENNSYLVANIA. 
By  Ralph  TV.  Stone, 
GENERAL  DESCRIPTION. 
The  Pittsburg  coal  seam  underlies  about  2,000  square  miles  in  the 
southwestern  part  of  Pennsylvania.  In  Greene  and  Washington 
counties  it  is  deeply  buried  beneath  the  surface,  but  to  the  north  and 
east  the  geologic  structure  is  such  that  the  coal  is  brought  to  a  higher 
elevation,  and  shows  hundreds  of  miles  of  outcrop  along  the  border  of 
the  main  field  and  in  detached  synclinal  basins.  The  northernmost 
remnant  of  the  Pittsburg  coal  is  a  small  area  which  lies  to  the  north- 
east of  the  main  body  of  the  coal  and  is  separated  from  it  by  the  valley 
of  Kiskiminitas  River.  The  field  on  the  north  side  of  the  river  lies 
along  the  Armstrong-Indiana  county  line  and  terminates  in  the  valley 
of  Crooked  Creek.  This  detached  portion  of  the  great  Pittsburg  coal 
field  takes  its  name  from  the  village  of  Elders  Ridge,  which  is  situated 
near  the  middle  of  the  area. 
Extent. — Geographically  the  limits  of  the  Elders  Ridge  coal  field  are 
clearly  defined.  It  is  bounded  on  the  north  by  Gobbler  Run,  on  the  east 
by  Blackleg  Creek,  on  the  south  by  Kiskiminitas  River,  and  on  the 
west  b}^  Long  Run.  It  is  about  9  miles  long  and  2^  miles  wide,  with 
the  long  axis  in  a  northeast-southwest  direction.  This  belt  of  coal  is 
divided  transversely  into  three  large  blocks  by  the  valleys  of  Whiskey 
Run  and  Big  Run,  which  have  cut  through  the  horizon  of  the  coal  and 
expose  long  lines  of  outcrop  on  both  sides  of  the  streams.  The  mid- 
dle one  of  these  three  blocks,  which  lies  between  Olivet  and  Clarks- 
burg, is  the  largest,  and  the  northernmost  is  the  smallest.  All  three 
have  irregular  outlines.  There  are  a  number  of  outliers  of  a  few  acres 
in  extent  on  the  northern  and  western  sides  of  the  field.  Roughly 
estimated,  there  are  about  1-1  square  miles  of  coal  in  this  area,  or 
between  8,500  and  9,000  acres.  Over  probably  600  to  700  acres  the 
coal  has  been  mined  out.     The  thickness  of  the  bed  will  average  close 
to  7  feet. 
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