1. Ocean floor Textbook pp 84-89
Chapter 3
Ocean floor
Textbook pp 84-89

2. Measuring Water Depth
Today's oceanographers use sonar instruments to generate a sound signal that is bounced or "echoed" off the sea floor and then recorded on board the ship. The speed of sound in water is 1,500 m per second, four times faster than the speed of sound in air. By carefully measuring the round-trip time of the sound waves and taking into account the variables of temperature and salinity, the depth of the water and the distance to another object can be measured accurately.

4. Ocean floor

5. Ocean Floor Bathymetry

8. Satellites tracking sea surface temperatures and currents

9. Alvin

10. Alvin
In 1979, scientists in Alvin dove to the Mid-Ocean Ridge in the eastern Pacific. A spectacular sight greeted them. Clouds of what looked like black smoke were billowing from tall chimneys on the ocean floor.

11. Hydrothermal vents

12. Hydrothermal vents
1.5 miles beneath the oceans surface on the seafloor, exists a strange and fascinating world that thrives in the absence of sunlight. Hydrothermal vents support a rich ecosystem that includes fish, shrimp, tubeworms, mussels, crabs, and clams. Hydrothermal Vents can be found on the ocean floor in areas with volcanic activity, where cracks allow seawater to seep beneath the earth’s crust. The water is heated up to 400 ° C (756 ° F) by the warmth of the Earth’s mantle, and it comes gushing out in what looks like plumes of smoke. The ‘smoke’ is actually superheated water rich with dissolved chemicals and metals. In the absence of sunlight specially adapted bacteria and similar organisms are able to convert the chemicals into useable bio-energy. This process is analogous to plants’ ability to use sunlight. The bacteria are the base of a hydrothermal vent community and allow the ecosystem to both exist and flourish.

15. Deep Flight

16. Jason II & Medea