What are the Deepest Parts of the Ocean? 

Many of the hardest-to-reach places within the world’s oceans are incredibly deep, making travel, extensive exploration, and the cataloging of species very difficult. Some of the deepest parts of the ocean include the Kermadec Trench, the Japan Trench, and the Philippine Trench. The best-known of all the ocean’s trenches is the Mariana Trench. It plummets to an incredible 10.9 kilometers or 7 miles (around 36,200 feet).

The deepest parts of the ocean are the startlingly vast trenches that are spread across the world. These trenches reach more than 30,000 feet beneath the surface and play host to some truly incredible species. 

Puerto Rico Trench 

Depth: 5.2 miles or 8.6 Kilometers

Coming in as the eighth deepest spot in the world’s oceans is the Puerto Rico Trench. It reaches a depth of 8.6 kilometers or 5.2 miles and is off the coast of the country of Puerto Rico. It’s in the Atlantic Ocean and is considered to be the deepest part of the Atlantic Ocean and the Caribbean Sea. 

Victor Vescovo was the first person to visit the bottom of the trench in 2018. His dive was also the second-deepest solo dive in history at the time it was completed. 

Japan Trench 

Depth: 5.5 miles or 9 kilometers

The Japan Trench is a deep submarine trench near the Japanese Islands. It’s part of the Pacific Ring of Fire and reaches a depth of 5.5 miles or 9 kilometers. The trench is also an incredible 800 kilometers or nearly 500 miles long. 

It was created when the Pacific Plate dropped beneath the Okhotsk Plate. The unstable continental plates in this area are also responsible for a great deal of destruction in Japan and surrounding islands (including tsunamis and earthquakes). 

An earthquake in 2011 resulted in record-shattering tsunami waves and a nuclear meltdown of the Fukushima Daiichi Nuclear Power Plant, and around 16,000 people died. 

Izu-Ogasawara Trench

Depth: 6 miles or 9.7 kilometers

The Izu-Ogasawara Trench is also known as the Izu-Bonin Trench and is located near the Japan and Mariana trenches. It is 32,087 feet at its deepest and was also created due to subduction. In this case, the Pacific Plate slipped beneath the Philippine Sea Plate. 

Kermadec Trench

Depth: 6.2 miles or 10 kilometers

The Kermadec Trench is the fifth deepest part of the ocean. It’s in the South Pacific Ocean and reaches 6.2 miles or 10 kilometers below the surface of the ocean. 

The trench formed by the Pacific Plate dropped underneath the Indo-Australian plate. It is part of the Kermadec-Tonga subduction system and changes very rapidly. The trench is 620 miles long, and when combined with the Tonga Trench just to the north, it reaches over 1,000 miles in length.

Amazingly, the second deepest fish in the world, the hadal snailfish, is endemic to the chromatic trench, living between 21,000 and 25,000 feet. It is also found in the Japan Trench. 

Kuril-Kamchatka Trench

Depth: 6.5 miles or 10.5 kilometers

The Kuril-Kamchatka Trench is the fourth deepest part of the world’s oceans. It’s also known simply as the Kuril Trench, and it’s found in the northwest Pacific Ocean. The trench resulted from the Pacific Plate subducting beneath the Okhotsk Plate. This area is also known for its volcanism. 

There are also major earthquakes associated with this area of the ocean. This includes a 9.0 magnitude earthquake recorded in 1952. Many other earthquakes, reaching levels of 8.4, 8.6, and more, have also been reported in this area.

Philippine Trench

Depth: 6.5 miles or 10.5 kilometers

The Philippine Trench is an incredibly deep point in the earth’s oceans, dipping 10.5 km below sea level, or more than 6.5 miles. The trench reaches an incredible length of 1,320 km and a width of up to 30 km. It’s east of the Philippines and was formed due to a collision between the Eurasian Plate and the Philippine Plate. It’s very closely situated to the Manila Trench, Sulu Trench, and Cotabato Trench. 

For a time, scientists believed that the Philippine Trench was the deepest point on the planet. But, in 1970, this changed.

Tonga Trench 

Depth: 6.7 miles or 10.8 kilometers

The second deepest point on Earth is the Tonga Trench. It is nearly 11 kilometers deep, and the deepest part of the trench is known as the Horizon Deep. It is second only to the Challenger Deep.

The trench is in the southwest Pacific Ocean and is the deepest point in the southern hemisphere. The Horizon Deep is named for a research vessel, the crew of which discovered this incredibly deep area of the ocean in 1952. 

Amazingly, despite the depth, there are species that live at the bottom of the Tonga trench. These include small amphipods, as well as some larger species of fish, like the barreleye fish, black dragon fish, and snailfish. 

Mariana Trench 

Depth: 6.85 miles or 11.03 kilometers

The Mariana Trench is well-known as the deepest place on Earth. The single deepest point in the trench is the Challenger Deep, sitting at between 35,768–35,856 ft. The trench has been measured by submersibles, some of which are remote-operated and benthic landers. 

The Mariana Trench is in the western Pacific Ocean near the Mariana Islands, from which it takes its name. The deepest part of the trench is named for the British Royal Navy ship, HMS Challenger. The crew of the Challenger was the first to record the trench’s depth (between 1872 and 1876). 

The trench presents a variety of challenges to those who would choose to explore it. This includes the incredibly dangerous pressure of 1,086 bars (15,750 psi). The trench is also 43 miles wide on average and stretches to a length of around 1,500 miles. 

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