THE DEEPEST POINT IN OCEAN: THE MARIANA TRENCH

The Mariana Trench, located in the Western Pacific Ocean, east of Mariana Islands, is the deepest part of the world's all oceans. The trench is about 2,550 kilometres long but is narrow in width, just about 69 kilometres on an average. It goes deep into the ocean about 10.91 kilometres or 35,800 ft. The place where the Mariana trench goes the deepest is known as Challenger Deep.

At the bottom of the trench, the water column exerts a pressure of 15,750 psi, that is over one thousand times the standard atmospheric pressure at sea level! At this pressure the density of water is increased by 4.96%, making ninety five litres of water under the pressure of the Challenger Deep contain the same mass as a hundred litres at the surface.

The Mariana Trench isn't really the deep, narrow furrow that the word "trench" implies. Rather, the abyss marks the location of a subduction zone.

Subduction zones occur where one part of the seabed—in this case the Pacific plate—dives beneath another, the Philippine plate. Though tectonic forces eventually warp the Pacific plate so that it makes a near vertical dive into the Earth's interior, at seabed level the plate dips at a relatively gentle angle.

One reason the Mariana Trench is so deep, is because the western Pacific is home to some of the oldest seafloor in the world - about 180 million years old.

Seafloor is formed as lava at mid ocean ridges. When it is fresh, lava is comparatively warm and buoyant, riding high on the underlying mantle.

But as lava ages and spreads away from its source, it slowly cools and becomes increasingly dense, causing it to settle ever lower - as is the case with the Mariana Trench.

Recently, Jame Cameron has travelled to the bottom of the Mariana Trench inside a specially designed submarine. He said he had visited “another planet” – desolate, foreboding and moon like – and it felt a bit lonely. ­"My feeling was one of complete isolation from all of humanity,” he said after returning from the Pacific Ocean’s deepest point.