Ocean Floor and Underwater Discovery

Studying the Ocean Floor Sonar- used on ocean surface Satellite- Seasat and Geosat- used in space

Sonar Sound Navigation and Ranging Scientists send sound waves to the bottom of the ocean by ship. The sound waves bounce off the ocean floor and return to the ship. The deeper the ocean , the longer it takes for the sound waves to return.

SONAR 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.

Seasat Satellites send images to Earth that measure direction and speed of ocean waves Seasat-1978

Geosat- Navy Satellite Military satellite Measures height of the ocean surface. Different underwater features affect the height of the water above them.

Mid-Ocean Ridge

Rift Valley Zone between the plates In the rift valley, which can be 15 to 30 miles (24 to 48 kilometers) wide, new oceanic crust is being made, which means lots of seismic activity is happening. Hydrothermal vents were discovered in rift valleys.

Rift Valley

Ocean Trench Huge cracks on ocean floor Created by oceanic plate pushing beneath continental plate or another oceanic plate Deep-sea trenches are the deepest parts of the ocean. The deepest one, the Marianas Trench in the South Pacific Ocean, is more than 35,000 feet (10,668 meters), or almost 6.6 miles (10.6 kilometers) deep. A Navy-owned submarine, the Trieste, still holds the record for diving to the bottom of the deepest part of the Marianas Trench, the Challenger Deep, on January 23,1960.

Bioluminescence Scientists estimate that 90 percent of deep-sea species are bioluminescent . Bioluminescence is the production of visible light by living organisms.

Seamounts Mountains of volcanic material Formed when magma pushes it way through or between tectonic plates If seamounts build up they can become volcanic islands; Example: Hawaiian Islands Seamounts are usually 25 miles (40 kilometers) in diameter and can be 10,000 to 15,000 feet (3000 to 4500 meters) tall.

Seamounts Less than 0.1 percent of the world's seamounts have been explored to learn what species live on them, but many of the species that have been found so far are new to science. It has been estimated that more than 30,000 seamounts reaching more than 1,000 meters tall are found in the Pacific Ocean. Approximately 800 are in the Atlantic Ocean, and an unknown number exist in the Indian Ocean. They usually have volcanic origins.

Alvin Alvin, the world's first deep-sea submersible Three-person, self-propelling capsule-like submarine nearly eight meters long. Alvin has an operational maximum depth of about 4,000 meters.

Shinkai 6500- Japan Shinkai 6500, a Japanese research submarine built in 1989, can work at depths down to 6,400 m. World's deepest-diving manned research submarine.

Study Questions 1. The Hawaiian Islands form from what type of ocean feature? 2. Where is pressure the greatest or the most intense? 3. What is sonar? 4. Underwater mountain range? 5. Underwater volcano? 6. Feature of the ocean that is at the edge of a continent? 7. Production of visible light by an organism? 8. Besides organisms in the ocean, what other organism can you think of that produces visible light? 9. The flat part of the ocean floor? 10. What makes up the continental margin? 11. What makes up the deep ocean basin? 12. Where do tectonic plates pull apart or move away from each other? 13. Deepest part of the ocean?

Answers 1. seamount 2. at the bottom of the ocean 3. Sound navigation and ranging- scientists send sound waves to the ocean floor and measure the time it takes for the sound waves to return 4. mid-ocean ridge 5. seamount 6. Continental shelf 7. Bioluminescence 8. fireflies/lightning bugs 9. abyssal plain 10. continental shelf, continental slope and continental rise 11.abyssal plain, mid-ocean ridge, rift valley, Ocean trench and seamount 12. Mid-ocean ridge 13. Ocean trench