Our oceans cover 70% of the Earth’s surface and contain diverse ecosystems that sustain a diversity of other-worldly creatures and other life forms.
At its deepest point, the ocean’s water pressure is so extreme it would theoretically dissolve bone, making it impossible for any vertebrates to survive.
Few humans have ever seen the deepest part of the ocean, and those that have found “only trace amounts of life.”
Nevertheless, scientists believe the “hydrothermal vents” found at such depths could provide the conditions needed for life on planet earth to form.
How Deep is the Deepest Part of the Ocean?
If you were asked, “How deep is the ocean?” what would your best guess be? A couple of miles? A few thousand meters?
The correct answer is 10,924 meters – the equivalent of around 6.788 miles – although the exact depth of the deepest spot in the ocean remains unknown.
If you were to stand on the sea floor at the deepest part of the ocean, you’d be 35,840 feet underwater.
If you swam from the surface, you’d cover 10.92 km before you reached the deepest place.
What is the Deepest Part of the Ocean?
On average, our Earth’s oceans are approximately 12,100 feet – the equivalent of 2.3 miles. In places, however, it plummets to breath-taking depths.
In the Indian Ocean, the Java Trench plunges to depths of around 24,000 feet, but that’s nothing compared to the depths of the Pacific Ocean.
The Mariana Trench is a crescent-shaped depression that runs parallel to the Mariana Islands, situated in the western Pacific Ocean, to the east of the Philippines.
Although the exact depth of the Mariana Trench remains unknown, scientists have used sound energy and solar to measure its depths, and found a section where it descends to nearly 11,000 meters.
In the Mariana Trench there are a collection of three pools or basins, collectively known as Challenger Deep.
Each pool measures between 6 to 10km in length and descend some 10,924 meters below sea level.
Here, the tectonic plates that make up the planet’s outer layer are constantly moving, growing, spreading, and grinding against one another.
The Mariana Trench was formed when two tectonic plates collided. The Pacific plate is larger and heavier than the younger Mariana plate, so when the two crashed into one another, the Pacific Plate plunged downward, creating a “subduction zone.”
As the two huge moving slabs slammed into one another, a “crescent-shaped wrinkle” appeared in the form “a 2,550 kilometer (1,580 miles) long groove” known as the Mariana Trench.
The Pacific tectonic plate is some 180 million years old, making it cooler and denser than its younger neighbors.
It’s been gradually descending for decades, and reached its deepest point where it collided with the Mariana plate.
At the same time, fault lines cut narrow grooves the Pacific plate, “allowing it to fold at a steeper angle than in other subduction zones.”
The same geologic process responsible for creating the Mariana Trench also helped form the tallest mountains.
In comparison to Challenger Deep, however, Everest is relatively small, standing just 8,849 m tall, the equivalent of around 5.5 miles or 8.8 km.
How Deep is Every Ocean?
The Pacific Ocean is the largest and deepest of the world’s oceans. It covers so much of planet Earth that “the whole of it cannot be seen from space.”
Its average depth is around 4,000 meters, or 13,000 feet, and it contains almost twice as much water as the Atlantic Ocean.
At its deepest, the Pacific Ocean floor lies some 10,924 meters, although some argue that Challenger Deep is even deeper than that, descending to more than 11,000 meters (36,000 feet).
The Pacific Ocean is also home to the second deepest part of the world’s seas.
The Tonga Trench lies in the southern end of the Pacific Ocean, between New Zealand, Fiji, Tonga and American Samoa.
Its deepest parts lie in Horizon Deep, where the ocean floor is some 10,800 m below sea level, making it the deepest point in the Southern Hemisphere.
Some of the other deepest zones in the Pacific Ocean include:
- The Kuril- Kamchatka Trench at 10.5 km
- The Kermadec Trench at 10.04 km
- The Izu-Ogasawara or Izu-Bonin Trench at 9.78km
- The Japan trench at 9km
The Atlantic Ocean separates South and North America from the continents of Europe and Africa.
It shares borders with 10 marginal seas, giving it a surface area of around 106,400,000 square km (41,100,000 sq mi), and an average depth of 11,962 feet (3,646 metres).
The deepest points of the Atlantic Ocean are in the Puerto Rico Trench, which lies between the Atlantic Ocean and the Caribbean Sea. Here, the ocean floor is 8,605 metres (28,232 ft) below sea level, making it “the deepest seafloor outside the Pacific Ocean.”
The Puerto Rico Trench was formed when two ocean plates converged, causing the North American plate to descend beneath the Caribbean plate.
The South Sandwich Trench is situated between the Atlantic and Southern Oceans and, where it extends into the Atlantic, has a maximum depth of around 8.42 km. This point is known as Meteor Deep.
On average, the Indian Ocean is deeper than the Atlantic, but shallower in its deepest zones. It has an average depth of 12,274 feet (3,741 m) deep and covers around 7% of the Earth’s surface.
Many people believe deepest point in the Indian Ocean to be located in the Java Trench near the islands of Sumatra and Java.
The Java Trench, also known as the Sunda Trench, is 3,200 km long and has a maximum depth of 23,595 feet (7192 meters).
Even deeper than that, however, is the lesser-known Diamantina Trench, located in the South East Indian Basin. It has a maximum depth of 8,047 meters (26,400 feet) and is a type of rift valley rather than a subduction trench.
It formed some 50 to 60 million years ago two of the Earth’s tectonic plates moved, separating Australia from Antartica.
Southern or Antarctic Ocean
The southern or Antarctic Ocean is slightly shallower than the Indian Ocean, with an average depth of 10,728 feet (3270 m). Parts of the Southern Ocean are portions of the world’s other oceans, including southern sections of the Pacific, Atlantic, and Indian Oceans.
Its deepest point is in the South Sandwich Trench, which lies between the Southern Ocean and the Atlantic.
The deepest place in the Southern Ocean is known as the Factorian Deep, and lies “nearly 24,400 feet (7,437 meters) below the sea surface.”
It was discovered in 2019, when American explorer and entrepreneur Victor Vescovo decided to “map the deepest points of the world’s five oceans.”
The Arctic Ocean is the smallest and shallowest of all the world’s oceans, covering just 14,060,000 km2 (5,430,000 sq mi).
Its deepest points are in Molloy Hole and Litke Deep, with Molloy Hole descending some 5,550 m (18,210 ft), and Litke Deep 5,449 m (17,877 ft).
The average depth of the Arctic Ocean is just 1361 m, due to it having “significantly larger continental shelves than other oceans.”
Have We Been to the Bottom of Every Ocean?
Only a handful of people have seen the deepest parts of our planet.
Jacques Piccard and Don Walsh
The first to experience what it feels like to be over 10,000 meters below the sea were Swiss engineer and oceanographer Jacques Piccard and U.S. Navy Lt. Don Walsh.
They reached a depth of 10,916 meters (35,814 ft) on 23rd January 1960 and remained the only people to have done so for over 50 years.
Piccard and Walsh descended in a deep-diving research submersible known as a bathyscaphe. Although one of the outer windows cracked during the descent, the dive was a success.
Despite that, no one has attempted another visit to Challenger Deep for over 50 years! In 2012, filmmaker James Cameron became the first person to solo dive to the depths of the ocean.
Cameron completed the dive using a submersible he designed himself. He reached a maximum depth of 10,898 meters (35,756 ft).
At that depth, Cameron said, “You don’t expect a profusion of life,” but he still came home with “68 new species,” proving life does exist in this lunar-like landscape.
In 2019, explorer and businessman Victor Vescovo broke the world record for the deepest dive ever when he descended 35,853 feet (10928 m) into the Mariana Trench.
He discovered life forms live even at these immense depths, spotting “arrowtooth eels at 9,843 feet” and supergiant amphipods (shell less crustaceans) at 26,247 feet.
As part of the Five Deeps Expedition crew, Vescovo also visited the deepest zones in the world’s other four oceans.
To date, he’s the only person to have reached the bottom of the Molloy Deep in the Arctic Ocean and the Java Trench in the Indian Ocean.
His also managed to overcome “logistical and weather-related challenges” to become the first person to successfully dive the South Sandwich Trench, reaching a maximum depth of 7,433.6 meters (24,388 feet).
Even with the latest technology, the deep sea remains a challenging place to visit. The extreme pressure, lack of sunlight, frigid temperatures, and remote locations mean our deep seas are still “least explored biome of Earth’s biosphere.”
Fun Facts About the Deepest Parts of the Ocean
#1 You Could Hide Mount Everest in the Mariana Trench
The world’s tallest mountain is just 8,849 m tall, so could fit into the deepest part of the Mariana Trench with over 2,000 meters to spare.
#2 The Pressure in the Mariana Trench is The Equivalent of 100 Elephants
The underwater pressure in the Mariana Trench over 1,000 times greater than the atmospheric pressure at sea level. At the bottom, the pressure reaches 15,750 psi, or around 8 tons per square inch. That’s the equivalent of roughly 100 elephants standing on your head!
#3 Even the Bottom of the Ocean is Noisy
In 2016, a group of researchers dropped a “titanium-encased hydrophone” into the Challenger Deep trough to record ambient noise.
The results surprised them! Rather than being the peaceful place Vescovo experienced from his “technological bubble” in the Mariana Trench, the noise never stops.
Researchers heard the distant calls of baleen whales, the rumbles of earthquakes, “and the clamor of a category 4 typhoon that just happened to pass overhead.”
#4 There is Life at the Bottom of the Mariana Trench
Few creatures live in the deepest parts of our oceans, but a handful of species do eke out an existence there.
Hadal snailfish are “flabby, translucent” creatures that live at depths of around 7,000 meters in the Mariana Trench.
As the pressure at this depth would crush bone, halal snailfish have cartilaginous skeletons “which is much more tolerant of high-pressure environments.”
The Mariana Trench is the deepest place on Earth, descending further below the ocean than Mount Everest rears above Earth.
Many more people have climbed Everest than have ever visited the deepest parts of our oceans, and our understanding of the so-called hadal zone of the ocean remains extremely limited.
The few people that have seen the deepest trenches in our oceans found little sign of life. The conditions down there are so extreme that only a handful of few species can survive down there.
Despite that, scientists believe that our deep oceans may hold the secret to life to Earth.
In the Mariana Trench are “deep, hydrothermal vents that spew mineral-rich seawater” that may have caused the chemical reactions necessary to create “increasingly complex organic compounds.”
The deepest zones in the world’s oceans still hold many secrets, and it could take years for us to develop the technology needed to unlock them.
Until then, hadal snailfish and translucent sea cucumbers can roam the sea floor unhindered.
Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.