46 



Physiography 



STATUTE 



MILES 



— 1200 



I 



REDONDO CANYON 



V X 5 



Figure 46. Cross sections of Redondo Canyon made from echo soundings at 60-foot intervals aboard R/V Velero IV. 

 Note fan at mouth. Shelf-breaks of profiles 3, 4, and 5 are nearly uniform, suggesting at least partial planation of the 

 shelf by wave erosion after the canyon was formed. Depths must be increased by 9 feet to correct for tide and keel 

 depth of hydrophone. 



mean that nickpoints do not exist but simply 

 that few of those shown on charts can be 

 considered as proven. The general lack of 

 tributaries along this part of the canyons is 

 also a reflection of the lesser density of 

 soundings far from shore compared to those 

 made nearer the canyon heads. As shown 

 by Figure 1 and the accompanying discus- 

 sion of Shepard and Emery (1941), the 

 sounding density at the outer parts of the 

 canyons may be more than an order of mag- 

 nitude less than at the heads. For this 

 reason, tributaries as large as Scripps Can- 

 yon could be completely overlooked if they 

 occur 5 or 10 miles from shore. In addi- 

 tion, the front of the sound wave from the 

 ship's echo sounder is an approximately 

 spherical surface. At great depth, reflection 

 of nearly all the sound from a fairly flat sur- 

 face into which such narrow slot-like tribu- 



taries may be cut would prevent the recogni- 

 tion of the tributaries. Again, we must 

 consider the limitations of survey methods 

 in comparing the characteristics of different 

 portions of the canyons. 



The outer part of the canyons, where they 

 leave the base of the slope and debouch on 

 the adjoining basin or trough floor, is even 

 less well known than the other two parts, 

 owing to greater distance from shore, 

 greater depth of water, and smaller cross 

 section of valley. In this area two forms 

 are taken, constructional and erosional. 

 The constructional form is that of a large 

 fan; although it has been referred to during 

 the past as a delta, the term delta implies a 

 control by sea level, but sea level actually 

 was probably not related in any way to the 

 feature. Fans exist at the mouths of the 

 Hueneme-Mugu group of five canyons and 



