1975 Volume 84 Issue 1 Pages 36-40
From the results of the bathymetric survey conducted by the Survey Ship SHOYO from 18 April to 13 May 1974, the following ocean bottom features have been confirmed :
1. All of the Kyushu-Palau Ridge, West Mariana Ridge and the knolls at the central part of the Philippine Basin present their profiles as gentle on their western slopes but steep on their eastern side.
2. On the western part of the bottom of each of the basins separated by the above mentioned ridges, a rugged sea knoll group exists, while a comparatively flat bottom extends at the eastern part.
3. The average depths of the Philippine Basin, West Mariana Basin and Mariana Trough are 5, 800 m, 4, 500 m and 3, 500 m, respectively, presenting a stepped feature separated by the ridges.