SECT. 2] 



TRENCHES 



421 



B 



\ 5000 



\ 



^. 



-6000 



\ 



-6000 



\ 



^ 



. 7000 



F' 



-7C^ 



V 



B' 



\ 



A 



:j 



•^ — 6000 





-f 



I 



r 



1 9000 / 



'\— 9000 --, f 



V 



\/ 



G' 



A /k i 



\ 10,000 — >»i«— 10.024 



-/ 



CROSSING NEARLY 

 PARALLELS TRENCH AXIS 



J' 



'NV 9500 



_/^ 



■■'J 



Fig. 4. Cross-sections of the Philippine Trench traced from R.V.^irang'ej- Precision Depth 

 Recorder tapes. Sounding scales corrected after Matthews (1939). (See Fig. 3 for 

 location of the sections.) Note: — Since a wide-beam sounder was employed, many 

 side echoes appear as early, late or faint returns. The upper surface, ordinarily 

 accepted as the sounding trace, is actually the envelope of minimum reflection times. 



15 — s. m 



