The Ocean FloorThe Ocean Floor

Chapter 13 Section 2Chapter 13 Section 2

Studying the Ocean FloorStudying the Ocean Floor

Sonar- used on ocean surfaceSonar- used on ocean surface

Satellite- Seasat and Geosat- used in Satellite- Seasat and Geosat- used in spacespace

SonarSonar

SoSound und NaNavigation and vigation and RRanginganging

Scientists Scientists send sound waves to the bottom send sound waves to the bottom of the ocean by shipof the ocean by ship..

The The sound waves bounce off the ocean sound waves bounce off the ocean floor and return to the ship.floor and return to the ship.

The The deeper the ocean , the longer it takes deeper the ocean , the longer it takes for the sound waves to returnfor the sound waves to return..

SONAR-FYISONAR-FYI

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

SeasatSeasatSatellites send images to Earth that Satellites send images to Earth that measure direction and speed of ocean measure direction and speed of ocean waveswaves

Seasat-1978

Geosat- Geosat- Navy SatelliteNavy Satellite

Military satelliteMilitary satellite

Measures height of the Measures height of the ocean surfaceocean surface..

Different underwater Different underwater features affect the features affect the height of the water height of the water above them.above them.

The Ocean FloorThe Ocean Floor

Continental shelfContinental shelfContinental slopeContinental slopeContinental riseContinental riseAbyssal PlainAbyssal PlainMid-ocean ridgeMid-ocean ridgeRift valleyRift valleyOcean trenchOcean trenchSeamountsSeamounts

You do not have to write all of these, just make sure they are your headings.

Continental shelf AContinental shelf AContinental slope BContinental slope BContinental rise CContinental rise CAbyssal Plain EAbyssal Plain EMid-ocean ridge FMid-ocean ridge FRift valley FRift valley FOcean trench HOcean trench HSeamounts D/GSeamounts D/G

    AA B

D E F G

H

C

Continental MarginContinental Margin

Made up of:Made up of: Continental shelfContinental shelf Continental slopeContinental slope Continental riseContinental rise

Continental ShelfContinental Shelf

Begins at the Begins at the shorelineshoreline

Continues until the ocean floor starts to Continues until the ocean floor starts to slopeslope

Depth Depth can reach about 200 meterscan reach about 200 meters

Continental SlopeContinental SlopeBegins atBegins at edge of edge of continental shelfcontinental shelf

Continues Continues down down toto the the flat part of the flat part of the ocean floorocean floor

Ranges Ranges between 200 meters to about between 200 meters to about 4000 meters4000 meters

Continental RiseContinental Rise

Base of continental slopeBase of continental slope

Made of large piles of sedimentMade of large piles of sediment

Deep Ocean BasinDeep Ocean Basin

Made up of:Made up of: Abyssal plainAbyssal plain Mid-ocean ridgeMid-ocean ridge Rift valleysRift valleys SeamountsSeamounts Ocean trenchesOcean trenches

Abyssal PlainAbyssal Plain

Large, Large, flat area of the ocean floorflat area of the ocean floor

Covered in mud and remains of tiny Covered in mud and remains of tiny marine organismsmarine organisms

Average depth 4000 metersAverage depth 4000 meters

Abyssal Plain

Mid-Ocean RidgeMid-Ocean Ridge

Underwater mountain rangesUnderwater mountain ranges

Form where tectonic plates pull apartForm where tectonic plates pull apart

Rising magma between the plates creates Rising magma between the plates creates the ridgethe ridge

Mid-Ocean RidgeMid-Ocean Ridge

Rift ValleyRift ValleyZone between the platesZone between the plates

In the rift valley, which In the rift valley, which can be 15 to 30can be 15 to 30 milesmiles (24 to 48 kilometers) (24 to 48 kilometers) widewide, , new new oceanic crust is being made, which means oceanic crust is being made, which means lots of seismic activity is happening. lots of seismic activity is happening.

Hydrothermal ventsHydrothermal vents were discovered in rift were discovered in rift valleys.valleys.

Rift ValleyRift Valley

Ocean TrenchOcean TrenchHuge cracks on ocean floorHuge cracks on ocean floorCreated by Created by oceanic plate pushing beneath oceanic plate pushing beneath continental plate or another oceanic platecontinental plate or another oceanic plateDeep-sea trenchesDeep-sea trenches are the are the deepest parts of the deepest parts of the ocean. ocean. The The deepest one, the Marianas Trenchdeepest one, the Marianas Trench in the in the South Pacific Ocean, is more than 35,000 feet South Pacific Ocean, is more than 35,000 feet (10,668 meters), or almost (10,668 meters), or almost 6.6 miles6.6 miles (10.6 (10.6 kilometers) kilometers) deep.deep. A Navy-owned submarine, the A Navy-owned submarine, the TriesteTrieste, still holds , still holds the record for diving to the bottom of the deepest the record for diving to the bottom of the deepest part of the Marianas Trench, the Challenger part of the Marianas Trench, the Challenger Deep, on January 23,1960.Deep, on January 23,1960.

Scientists estimate that Scientists estimate that 90 percent of 90 percent of deep-sea species are bioluminescentdeep-sea species are bioluminescent . .

Bioluminescence is the Bioluminescence is the production of production of visible light by living organismsvisible light by living organisms. .

BioluminescenceBioluminescence

SeamountsSeamounts

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

SeamountsSeamounts

Less than 0.1 percent of the world's seamounts Less than 0.1 percent of the world's seamounts have been exploredhave been explored to learn what species live on to learn what species live on them, but many of the species that have been them, but many of the species that have been found so far are new to science. found so far are new to science.

It has been estimated that more than 30,000 It has been estimated that more than 30,000 seamounts reaching more than 1,000 meters tall seamounts reaching more than 1,000 meters tall are found in the Pacific Ocean. Approximately are found in the Pacific Ocean. Approximately 800 are in the Atlantic Ocean, and an unknown 800 are in the Atlantic Ocean, and an unknown number exist in the Indian Ocean. number exist in the Indian Ocean.

They usually have volcanic originsThey usually have volcanic origins. .

AlvinAlvin

Alvin,Alvin, the world's first deep-sea the world's first deep-sea submersiblesubmersible

Three-personThree-person, self-propelling capsule-like , self-propelling capsule-like submarine submarine nearly eight meters long. nearly eight meters long.

Alvin has an operational maximum depth Alvin has an operational maximum depth of about 4,000 meters.of about 4,000 meters.

Shinkai 6500- JapanShinkai 6500- Japan

Shinkai 6500,Shinkai 6500, a Japanese research a Japanese research submarine built in 1989, can work at submarine built in 1989, can work at depths down to 6,400 m.depths down to 6,400 m.

World's deepest-diving manned research World's deepest-diving manned research submarine. submarine.

Study QuestionsStudy Questions1. The Hawaiian Islands form from what type of ocean 1. The Hawaiian Islands form from what type of ocean feature?feature?2. Where is pressure the greatest or the most intense?2. Where is pressure the greatest or the most intense?3. What is sonar?3. What is sonar?4. Underwater mountain range?4. Underwater mountain range?5. Underwater volcano?5. Underwater volcano?6. Feature of the ocean that is at the edge of a 6. Feature of the ocean that is at the edge of a continent?continent?7. Production of visible light by an organism?7. Production of visible light by an organism?8. Besides organisms in the ocean, what other organism 8. Besides organisms in the ocean, what other organism can you think of that produces visible light? can you think of that produces visible light? 9. The flat part of the ocean floor?9. The flat part of the ocean floor?10. What makes up the continental margin?10. What makes up the continental margin?11. What makes up the deep ocean basin?11. What makes up the deep ocean basin?12. Where do tectonic plates pull apart or move away 12. Where do tectonic plates pull apart or move away from each other?from each other?13. Deepest part of the ocean?13. Deepest part of the ocean?

AnswersAnswers1. seamount1. seamount2. at the bottom of the ocean2. at the bottom of the ocean3. Sound navigation and ranging- scientists send sound 3. Sound navigation and ranging- scientists send sound waves to the ocean floor and measure the time it takes waves to the ocean floor and measure the time it takes for the sound waves to returnfor the sound waves to return4. mid-ocean ridge4. mid-ocean ridge5. seamount5. seamount6. Continental shelf6. Continental shelf7. Bioluminescence7. Bioluminescence8. fireflies/lightning bugs8. fireflies/lightning bugs9. abyssal plain9. abyssal plain10. continental shelf, continental slope and continental 10. continental shelf, continental slope and continental riserise11.abyssal plain, mid-ocean ridge, rift valley, Ocean 11.abyssal plain, mid-ocean ridge, rift valley, Ocean trench and seamounttrench and seamount12. Mid-ocean ridge12. Mid-ocean ridge13. Ocean trench13. Ocean trench

The Ocean FloorThe Ocean FloorThe continents lie on the The continents lie on the continental platescontinental plates. The edges of these plates are under . The edges of these plates are under water, and they form the water, and they form the continental shelvescontinental shelves. These shelves slope outward very . These shelves slope outward very gently towards the ocean depths. In some places these shelves go out a long way, up gently towards the ocean depths. In some places these shelves go out a long way, up to 900 miles: In other places the shelves are much narrower. These shelves are fairly to 900 miles: In other places the shelves are much narrower. These shelves are fairly smooth because debris from the land is falling onto them from the water. This debris smooth because debris from the land is falling onto them from the water. This debris contains nutrients washed down from the land, and these nutrients, plus the shallow contains nutrients washed down from the land, and these nutrients, plus the shallow water, contribute to the abundance of life forms near the continents.water, contribute to the abundance of life forms near the continents.          Where the continental shelves end, there is a steep drop downwards. This is Where the continental shelves end, there is a steep drop downwards. This is called the called the continental slopecontinental slope. It plunges down into the dark, cold waters of the ocean. . It plunges down into the dark, cold waters of the ocean. At the bottom of the continental slope there is a an area that slopes gradually At the bottom of the continental slope there is a an area that slopes gradually downward to blend into the downward to blend into the abyssal plainabyssal plain. This is the bottom of the ocean as we think . This is the bottom of the ocean as we think of it.of it.          The ocean floor seems like a different world. There is no sun light down here. The The ocean floor seems like a different world. There is no sun light down here. The water is very cold. The pressure of the weight of miles of water above this area would water is very cold. The pressure of the weight of miles of water above this area would easily crush a submarine. Tiny flecks of material from the sunlit world float downward easily crush a submarine. Tiny flecks of material from the sunlit world float downward and eventually settle on the bottom. There is almost nothing to eat, and the animals and eventually settle on the bottom. There is almost nothing to eat, and the animals that live here are few and far between. There are many different kinds of animals, but that live here are few and far between. There are many different kinds of animals, but they are small and widely scattered. They are able to survive on very little.they are small and widely scattered. They are able to survive on very little.          However, it is not all silence and darkness here. The earth's crust is thinnest in the However, it is not all silence and darkness here. The earth's crust is thinnest in the ocean basins, and volcanic eruptions are part of this environment.  Here and there ocean basins, and volcanic eruptions are part of this environment.  Here and there isolated peaks called sea mounts rise above the flat abyssal plain. However, the most isolated peaks called sea mounts rise above the flat abyssal plain. However, the most active part of deep ocean geology occurs in the deep sea trenches, where the ocean active part of deep ocean geology occurs in the deep sea trenches, where the ocean floor is spreading apart. Lava comes up through the fissures, building up mountains floor is spreading apart. Lava comes up through the fissures, building up mountains and deep sea vents, called smokers. The constantly up-welling lava pushes the sea and deep sea vents, called smokers. The constantly up-welling lava pushes the sea floor away from the trenches and out towards the continents. When the sea floor floor away from the trenches and out towards the continents. When the sea floor reaches the continental plates, it subducts, or slides underneath them, carrying the reaches the continental plates, it subducts, or slides underneath them, carrying the cold rocky floor back into the hot mantle of the earth. cold rocky floor back into the hot mantle of the earth.