It forms the deepest depth zone of the oceanic floor that exists beyond the limit of abyssal zone.
It is indeed a deep trench zone where the depth of the floor is more than 6.5 km (6500 m) below the mean sea level. This depth bears the very deep part of the oceanic trenches.
The deepest oceanic trough / trench is that of the Mariana Trench located near the island of Guam in the Western Pacific ocean at a depth of 11.035 km (11035 m) below mean sea level. This depth is more than 2 km as compared to the height of the Mount Everest (8848 m) which is the highest point on the land. The hadal depth zone has the shortest areal coverage amongst the various depth zones. It is the darkest zone that hardly supports any marine organism.