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10 Fascinating Facts About the Deep Ocean

Amanda is a retired educator with many years of experience teaching children of all ages and abilities in a wide range of contexts.

Most of the deep ocean floor remains unexplored

Most of the deep ocean floor remains unexplored

Deep Ocean: The Last Great Frontier

While we've explored almost the entire surface of our planet, put people on the Moon, and sent robots into the far corners of the solar system and beyond, we still know very little about the deepest waters of our oceans.

It's dark down there, beyond the reach of sunlight. There's also huge pressure, making it impossible for humans to venture to the bottom of the ocean without being crushed.

But despite these many difficulties, science has been able to discover many of the secrets of what lies beneath the ocean waves. As new technologies and techniques develop, we are able to uncover more and more of the mysteries of the deep ocean.

Are you ready to venture into the watery depths? Then climb into the submersible, check your breathing apparatus, and come with me on a journey to the last frontier, where we'll uncover 10 fascinating facts about the deep ocean floor.

1. Features of the Ocean Floor

The ocean floor is where the earth's crust is created and destroyed. Volcanic activity associated with mid-ocean ridges and subduction zones creates many of the most striking and interesting features of the ocean floor.

Continental Shelf

The continental shelf is the gently sloping rim of the continent where the land mass meets the sea.

Continental Slope

The continental slope descends steeply from the continental shelf into the abyssal plain.

Abyssal Plain

About 3,500 to 5,500 m (11,480 to 18,040 feet) below sea level is a vast plain covered with deep sediment, called the abyssal plain.

Continental Rise

Below the steep continental slope, sediment may collect to form a gentler slope known as the continental rise.

An illustration showing the key features of the ocean floor leading down to the abyssal plain

An illustration showing the key features of the ocean floor leading down to the abyssal plain

Submarine Canyon

A river flowing off the land into the sea may carve a deep canyon in the ocean floor.

Mid-Ocean Ridge

A long, undersea mountain range runs along the mid-ocean ridge, where two tectonic plates are pulling apart.

Seamount

A seamount is an underwater volcano that rises 1,000 m (3,280 feet) or more above the surrounding plain.

Guyot

A guyot is a flat-topped seamount that once rose above the surface of the ocean as a volcanic island.


A computer generated image created from bathymetric data, showing the Bear guyot in the foreground and the Physalia seamount behind

A computer generated image created from bathymetric data, showing the Bear guyot in the foreground and the Physalia seamount behind

Island Arc

A curved line of volcanic islands, called an island arc, often forms close to a subduction zone.

Trench

A deep trough may form at a subduction zone, where one plate plunges beneath another. The ocean floor is destroyed at subduction zones. Deep-sea trenches are about 100 km (62 miles) wide. They may be thousands of yards long.

Illustration of the deep sea Atlantic trench

Illustration of the deep sea Atlantic trench

2. Major Ridges and Trenches

The major features of the ocean floor form at the boundaries of the plates that make up the earth's crust. Mid-ocean ridges form where two plates are pulling apart. Trenches form at subduction zones, where one plate is plunging beneath another.

Vast undersea mountain ranges form where two tectonic plates are pulling apart.

Computer generated image based on satellite data, showing the major mid-ocean ridges and deep sea trenches of the world's oceans

Computer generated image based on satellite data, showing the major mid-ocean ridges and deep sea trenches of the world's oceans

3. The World's Deepest Sea Trenches

The depth of deep sea trenches is measured from sea level.

A table showing the depth in metres and feet of the 10 deepest ocean trenches in the world

TrenchOceanDepth in m (feet)

Mariana

West Pacific

10,920 (35,827)

Tonga

South Pacific

10,800 (35,433)

Philippine

West Pacific

10,057 (32,995)

Kermadec

South Pacific

10,047 (32,963)

Izu-Ogasawara

West Pacific

9,780 (32,087)

Kuril

West Pacific

9,550 (31,332)

North New Hebrides

South Pacific

9,175 (30,102)

New Britain

South Pacific

8,940 (29,331)

Puerto Rico

West Atlantic

8,605 (28,232)

Yap

West Pacific

8,527 (27,976)

4. Smokers (Hydrothermal Vents)

Smokers are tall, chimney-like vents on the ocean floor that belch out clouds of super-heated water. They occur at volcanically active spots on mid-ocean ridges.

Smokers were first discovered in 1977 by a team on board the American submersible, "Alvin".

Smokers are created as water seeps down deep into the sea floor where it is heated by volcanic activity. The heated water then rises back to the surface. "Chimneys" up to 50 m (164 feet) high build up from minerals deposited by the heated water. The heated water rises up the chimney and erupts in tail jets. It can be as hot as 350 degrees Celsius (662 degrees Fahrenheit).

Smokers also support strange life forms that derive energy not from the sun as other life forms on Earth, but from volcanic activity.

5. Ocean Floor Sediment

Close to the coast, sediment consists mainly of mud, sand, and silt washed off the land by rivers. The deep ocean floor is blanketed with ooze (the remains of dead marine plants and animals). The amount of sediment and ooze can help scientists to calculate the age of the ocean floor.

Newly formed Rock

At the mid-ocean ridge, the new volcanic rock of the ocean floor is almost free of sediment.

5 Million Years Later

The rock has moved 500 km (311 miles) from the ridge. Sediment has started to gather in hollows.

10 Million Years Later

The rock has moved 1,000 km (621 miles) from the ridge. It is now covered with a thick blanket of sediment.

6. Mapping and Sampling the Ocean Floor

Early explorations of the ocean floor were made from ships using a lead weight and line to estimate depth. Today, scientists use echo-sounding techniques. They also use special submarines called submersibles, which may have people inside or be entirely robotic, to descend to the very depths of the ocean.

A photograph taken from inside a deep sea submersible craft, showing a robotic arm lifting a sample trap from the ocean floor

A photograph taken from inside a deep sea submersible craft, showing a robotic arm lifting a sample trap from the ocean floor

7. Fascinating Ocean Numbers

  • A particle of ooze sinks 0.3 to 3 m (1 to 10 feet) per day. At this rate, it would take 25 years for the remains of a dead shrimp to sink from the ocean surface to the floor of a deep-sea trench
  • The tube worm, Alvinella pompejana can live on "smoker" walls where the temperature is 105 degrees Celsius (221 degrees Fahrenheit), much higher than any land animal could tolerate
  • The Mariana trench could hold 28 Empire State Buildings standing on top of each other
  • The oldest parts of the ocean floor are about 200 million years old. The oldest rock found on land are about 3.5 billion years old
The tube worm, Alvinella pompejana, can survive at extreme temperatures on the side of a deep sea hydrothermal vent

The tube worm, Alvinella pompejana, can survive at extreme temperatures on the side of a deep sea hydrothermal vent

8. What Can You Find On the Ocean Floor?

Many useful products are found on or under the ocean floor. They include:

  • diamonds
  • oil
  • gas
  • coal
  • sand
  • metals

Diamonds are formed in shallow waters off the coasts of Africa and Indonesia. Sand, gravel, and limestone are often found in near-coastal waters. Coal id mined beneath the sea as well as on land. About 20% of oil comes from the ocean floor. Natural gas is found together with oil deposits.

9. The Formation of Oil and Gas on the Ocean Floor

Under certain conditions, oil and gas form from the remains of dead plants and animals that accumulate on the floor of shallow seas. This happens by a three-stage process:

  1. Dead plants and animals sink down to the floor of the continental shelf. Bacteria break the remains down into organic material
  2. Sediments of mud and sand washed off the land by rivers form layers of sandstone, covering the organic remains
  3. Increased pressure from further layers of sandstone and other sedimentary rock turns the organic remains into oil and gas

10. The Highest Seamount and Deepest Submarine Canyon

The highest seamount is near the Tonga trench between Samoa and New Zealand. The deepest submarine canyon is 40 km (25 miles) south of Esperance, Australia.

On land, Mount Everest is the highest mountain, at 8,848 m (29,028 feet) high. The highest seamount is 8, 705 m (28,560 feet) high.

The Grand Canyon is the deepest canyon on land, at 1,676 m (5,499 feet) deep. The deepest submarine canyon sinks down 1,800 m (5,906 feet).

A Last Word

That brings us to the end of our exploration of the wonders and the mysteries of the ocean floor. While most people think of outer space as the final frontier of human exploration, most of the deepest ocean remains unexplored. Who knows what discoveries may yet be made as we develop better technologies for probing into the watery depths of the world's oceans? Perhaps you will be an oceanographer or marine biologist and help make the exciting discoveries of the future!

© 2019 Amanda Littlejohn

Comments

Amanda Littlejohn (author) on January 19, 2019:

Hi Shelley,

Thanks so much for your comment. I'm so glad you learned something new. Strictly speaking "smokers" are called hydrothermal vents, but most marine scientists use the colloquial term.

FlourishAnyway from USA on January 18, 2019:

What a great article! I never heard of smokers and chimneys in reference to the ocean so I definitely learned something here. It’s hard to imagine any life form could tolerate the heat.

Amanda Littlejohn (author) on January 16, 2019:

Thanks, Earthsupport. I'm glad you enjoyed reading about the ocean floor.

Amanda Littlejohn (author) on January 16, 2019:

Hi Leland,

Well, there's a lot to be said for learning for learning's sake. :)

Earthsupport on January 16, 2019:

nice job with it.

Leland Johnson from Midland MI on January 16, 2019:

You're welcome, and I think you're right- it's never too late, but I'm not sure I would still have the nerve for it now. I might just be relegated to watching documentaries :)

Amanda Littlejohn (author) on January 16, 2019:

Hi Leland,

Thanks for your comment. Yes, Jacque Cousteau's films were marvelous, weren't they? If you still want to be a marine biologist, it's never too late!

Leland Johnson from Midland MI on January 15, 2019:

Amanda- great job with this article. I always wanted to be a marine biologist. I used to watch Jacque Cousteau specials and wish so badly to explore the oceans. I liked your "last word" finish as well. It's so true- there is so much ocean yet to be explored! Fascinating topic!