4. Mass physical properties of the sediment and rock. 



a. The mass physical properties having effects 

 on acoustic transmission (such as sound speed and attenuation 

 at various frequencies; density; porosity; and elastic prop- 

 erties) and their lateral and vertical gradients. Appendix A 

 details these sediment properties. 



5. Miscellaneous. 



a. The vertical sound-velocity gradient (in micro- 

 detail) in the sea water for several hundred meters above 

 the bottom. 



b. Chemical properties of the bottom water. 



c. Physical chemistry of the sediment and rock 

 masses (including pore water) and the mineralogy of the 

 constituents. 



d. Heat-flow measurements within the sediment 

 body. 



All of these items, of course, can never be fully de- 

 termined for any actual segment of the sea floor, especially 

 in deeper waters. In subsequent sections, general infor- 

 mation on some of these items will be summarized in 

 tables or short statements; the specific areas under con- 

 sideration will be described more fully. 



METHODS OF CONSTRUCTING A MODEL 



Chart Production 



Echo sounding and ship positioning are essential to 

 production of any chart, and the worth of the chart is a 

 direct reflection of the care and techniques employed. Any 

 chart not based on information gained by electronic ship 

 positioning is almost certainly in serious error in rough 

 terrain. 



