Geography: What lies beneath

Published June 19, 2010

Oceanic trenches are narrow valleys formed under the sea when one tectonic plate forces the other to bend downwards, creating a deep ditch into the ocean floor. In this article we will discuss five of the deepest ocean trenches in the world which are all located in the Pacific Ocean.

Mariana Trench
The Mariana Trench is situated in the Western Pacific Ocean and is the deepest known point on Earth. It is located to the east of the Mariana Islands, which, however, are situated to the south of Japan. The Mariana Trench takes a shape of a semi-circle and has a maximum depth of 35,798 feet, with an average width of 70 kilometres. Its total length is nearly 2,500 kilometres. The total depth of the Mariana Trench into the ground is more than Mount Everest's total height above the ground.

To better explain the magnitude of the Mariana Trench, imagine if Mount Everest is placed inside the Mariana Trench, then the peak of Mount Everest would be 6,800 feet lower than the opening of the Mariana Trench. The end of this trench is called The Challenger Deep, which got its name by the Challenger Expedition of 1951. It was the first expedition which analysed the depth of this trench using echo sounding.

Tonga Trench
The Tonga Trench is 35,702 feet deep and is also known as Horizon Deep. The Tonga Trench is located adjacent to the Kermadec Islands which are volcanic in nature, located northeast of New Zealand. The trench is situated at the northern part of the Kermadec-Tonga Subduction Zone, which is a convergent plate boundary. A convergent plate boundary is a phenomenon in plate tectonics, where two plates collide into one another and form volcanoes and mountains.

Philippine Trench
The Philippine Trench, also known as Philippine Deep or Mindanao Trench, is nearly 34,580 feet deep, making it the world's third deepest trench. The Philippine Trench was first explored by Emden, a German vessel in 1927. This trench is also called Mindanao Trench as it is located near the Mindanao Island, the second largest island of the Philippine (by area).

The world's largest deposits of heavy hydrogen, used in nuclear science, biochemistry and environmental sciences are also found in and around the Philippine Trench.

Kuril Trench
The Kuril Trench or the Kuril-Kamchatka Trench is the fourth deepest oceanic trench having a maximum depth of 34,449 feet. This trench was formed during the Cretaceous period, which was nearly 65 million years ago. The collision of the plates beneath this region formed this trench and also formed The Kuril Islands, which are a cluster of volcanic islands stretching from Japan to Russia having a total length of 1,300 kilometres.

Kermadec Trench
The Kermadec Trench is the fifth deepest trench formed by the collision of the Pacific Plate with the Indo-Australian Plate. It is nearly 32,963 feet deep and 1200 kilometres in length. This trench was discovered in 1952 by a Danish expedition. It was named Kermadec Trench as it is located east of the Kermadec Islands, which are a part of New Zealand.

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