-400 



-300 



-200 



-100 100 



Distance km 



200 



300 



400 



Fig. 19. Crustal section across continental margin near San Francisco computed from 

 surface geology and gravity data. (After Thompson and Talwani, 1959.) 



PROJECTED DISTANCE IS KM 

 JOO 200 300 400 500 



~7db ' ^25d ' ^» ' ^ ' '55o' 



PROJECTED DISTANCE IS KM 



Fig. 20. Gravity and topographic sections across the Mid -Atlantic Ridge. (After Talwani, 

 Heezen and Worzel, 1961.) 



