How Was the Mariana Trench Formed?

You may have heard of the highest mountain or the biggest desert in the world, but have you ever wondered about the deepest trench within the world’s oceans? Indeed, there is a deepest-known trench in the world’s oceans, known as the Mariana Trench. 

The crescent-shaped Mariana Trench formed through a process known as subduction. This is the process where the Pacific Plate collided with the Mariana Plate, generating intense pressure and friction that forces the oceanic crust to bend, creating a deep trench. 

Read below to learn more about the Mariana Trench. 

What is Mariana Trench?

The Mariana Trench is a crescent-like fissure in the Earth’s crust that extends over 1,500 miles (2,550 kilometers) in length and an average of 43 miles (69 kilometers) in width. It is situated in the western Pacific Ocean, east of the Philippines. 

It is Earth’s deepest known oceanic trench. Its lowest point is referred to as the Challenger Deep which extends to a maximum depth of around 10,925 meters (35,843 feet). The Mariana Trench was named after the adjacent Mariana Islands. 

How Was the Mariana Trench Formed? 

The Mariana Trench formed about 170 million years ago when the Mariana Plate was subducted by the Pacific Plate. The Earth’s crust, also known as the lithosphere, is made up of many slow-moving plates. These plates float above the molten rock that constitutes the mantle of the Earth.

Subduction is a process that occurs at the boundary of tectonic plates. When two plates crash into each other at high speed, one of them will inevitably push underneath (subduct) the other. The Pacific Plate is the largest of the seven major tectonic plates, encompassing over 95% of the Earth’s area. 

It covers a significant portion of the Pacific Ocean or an area of around 103,300,000 square kilometers.  The Mariana Plate, on the other hand, is a tiny tectonic plate that may be found on the west of the Mariana Trench. This tectonic plate serves as the foundation for the Mariana Islands, which are part of the Izu-Bonin-Mariana Arc.  

Key Facts About the Mariana Trench

Many people may not know much about Mariana Trench. However, there is a wealth of interesting information about this region. Let’s discuss some of these below. 

Environmental Condition

The Mariana Trench is marked by its severe environmental conditions, which include high pressure, low temperatures, and complete darkness. These conditions pave the way for a unique environment that becomes home to numerous peculiar species, some of which can be seen nowhere else on our planet.  

The study of the Mariana Trench offers significant insights into the characteristics of deep-sea biodiversity, adaptations to harsh environments, and the confines of life on Earth.


The Mariana Trench has been the focus of a significant amount of scientific investigation, with the assistance of deep-sea submersibles and remotely operated vehicles (ROVs). The bathyscaphe Trieste made the first manned descent to Challenger Deep in 1960, and since then, expeditions have remained active in exploring the Mariana Trench to learn more about its biology, geology, and ecology.

Ecological Concerns 

Similar to other oceanic trenches, the Mariana Trench is distant and difficult to access; nevertheless, it is not immune to human influences. The fragile and distinct ecosystems of the Mariana Trench are under threat from human activities, including deep-sea mining, pollution, and global warming. 

There is a growing consensus that this delicate ecosystem requires careful and long-term planning for its maintenance. 

One of the reasons that the Challenger Deep has remained mysterious to a great extent is because of its hydrostatic pressure. When you enter a body of water and start diving below the surface, the deeper you go, the more water surrounds you. If there are more gallons of water between you and the surface, the pressure on your body will increase likewise.  

When you dive deep into a pool, you may experience a sensation similar to squeezing or pushing in your eardrums due to hydrostatic pressure. When you double that feeling by thousands, you can begin to imagine how terrible the pressure would be in the Challenger Deep, which is located approximately seven miles of water above. 

Life in Mariana Trench

Water pressures reach over 15,750 psi at the trench bottom. This is about 1,071 times higher when compared to the pressure at sea level. At this depth, the water’s density rises to around 5%, and the temperature falls to almost freezing. 

In the past, scientists believed that it was impossible for anything to survive in the Mariana Trench due to the extreme conditions present in the region. However, they were surprised when Piccard and Walsh came across large creatures living at the bottom of the Mariana Trench during their expedition in 1960. 

Both men reported observing life forms resembling sea cucumbers, in addition to large-sized shrimp. Later expeditions provided more evidence of numerous other lifeforms in the Mariana Trench. These lifeforms include single-celled foraminiferans, tiny amphipods, and snailfish. 

In addition to that, some researchers have also recorded the sound of baleen whales inside the Mariana Trench. Having said that, there have been no discoveries of whales or other huge animals at the bottom of the trench. 

Pollution inside the Mariana Trench

Researchers have come across vast amounts of pollution throughout the Mariana Trench over the course of multiple expeditions. In 2016, an expedition was successful in recovering species that contained high levels of PCBs. 

In the 1970s, these harmful chemicals were banned because of the damage they cause to both plants and animals. In addition, the researchers verified that every single amphipod that was examined in the trench had a certain amount of microplastic waste in their stomachs. 

In 2019, scientists discovered carbon-14 radiation from nuclear bomb tests in the trench along with plastic bags and candy wrappers. 


So, the Mariana Trench is a deep trench formed due to the collision between the Pacific and Mariana plates. Researchers found traces of marine life in the Mariana Trench, but unfortunately, they also discovered high levels of toxic chemicals that can harm these creatures. It is essential to ensure the protection of these creatures from harmful waste materials.

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