MARINE SCIENCE 111 



It is rich in plant and fish life and other resources. The shelf begins 

 at the coastline and extends seaward in gentle sloping plains. 



Slide No. 11. Continental Slope: Once beyond tlie edge of the shelf, 

 the steeper Continental Slope begins — with its gathering darkness, 

 growing pressure, and the absence of all forms of plantlife. These 

 slopes are the most imposing features of the surface of the earth, in- 

 terlaced with submerged canyons, in some places reaching the impres- 

 sive depths of over 36,000 feet. 



Slide No. 12. Bottom Sediment : The floors of the deep ocean basins 

 are probably as old as the sea itself. Here in the eternal cold and 

 darkness lie the undersea mountain ranges and the strange, fiat-topped 

 sea mounts. Underlying the ocean bottoms are a number of sedimen- 

 tary layers, averaging one-half mile in depth — the product of a bil- 

 lion years of deposits of debris. 



Slide No. 13. Waves : Although the sea is impressive from a stand- 

 point of sheer size and depth, an even more impressive characteristic 

 is the constant motion of the sea in the form of waves, tides, and cur- 

 rents. Most waves are a result of the action of wind on water. 



Slide No. 13A. Breakers: The force of waves is almost incredible. 

 It is estimated that a 12-foot wave strikes wdth a force of 113 tons for 

 every foot of its width. 



Slide No. 14 : Tides, Sun, Moon, Earth : Tides are another form of 

 mass movement of the oceans. There is no drop of water in the ocean, 

 not even on the deepest ocean floor, that does not respond to the forces 

 that create the tides. No other force which affects the sea is so strong. 

 Tides are the natural result of the gravitational pull of the Sun and 

 the Moon. 



Slide No. 15. Global Thermostat: Because water is unique in its 

 heat transfer characteristics, the oceans act as a global thermostat. 

 They keep temperatures within limits which can support life. They 

 regulate the world's climate and weather. 



Slide No. 16. Ocean Currents : By redistributing heat received from 

 the Sun, ocean currents are a major factor which tend to make up for 

 the uneven heating of the globe. 



The currents are literally rivers in the sea — some with a volume of 

 flow that makes the Amazon a meadow brook by comparison. 



Slide No. 17. Gulf Stream : Perhaps the best known example is the 

 Gulf Stream which keeps Great Britain 35° warmer than would be 

 normally expected at her latitude. 



This current, 40 miles wide and 3,000 feet deep, moves more than 

 50 miles a day up the coast of Florida toward Cape Hatteras where 

 it turns eastward toward Europe and then divides into several 

 branches. One branch moderates the climate of north(>rn Europe 

 turning around North Cape to give Eussia its ice free Murmansk 

 coast. Another branch turns toward Africa and the Azores then 

 westward across the Atlantic. 



Slide No. 18. Humboldt Current: In contrast to the warm Gulf 

 Stream is the cold Hmnboldt Current, which flows up the west coast 

 of South America. As a result of this cold current less than 1 inch 

 of rain per year falls on the arid western coast. For no apparent 

 reason, a small shift in the course of the Humboldt Current occui^s 

 about once every 10 years and brings disaster in the form of torrential 

 rain and floods. 



