core catcher, as shown in figure 6-7. When 

 the cormg tube is driven into the ocean floor, 

 friction will exercise a downward pull on the 

 core sample which is opposed by the hydrostatic 

 pressure on the ocean bottom. The hydrostatic 

 pressure will not allow a vacuum to be created 

 betweeii the piston and the top of the core so 



long as the frictional forces do not exceed the 

 hydrostatic pressure. As the coring tube 

 penetrates the sea floor, the friction created will 

 always cause the pressure immediately below 

 the piston to be diminished as compared with 

 the hydrostatic pressure. The difference in 

 pressure between the mouth of the coring 



FREE FALL 



PARTIAL 

 PENETRATION 



FULL 

 PENETRATION 



HAULING IN 



n 



ir 



LOWERING 

 CABLE 



ICORER 



11 



ir 



-PISTON 



TRIGGER LINE 



A 



1 



n 



A 



TRIGGER 

 WEIGHT 



n 



w 



SEA BOTTOM 



^////////////////// 



58 



Figure 6-7. Principle of operation of piston corers. 



H. 0. 607 



(J 



