 The hadal zone (named after Hades, the Greek god of the underworld) is a zone designated for the deepest trenches in the world, reaching depths of below .The deepest point in the hadal zone is the Marianas Trench, which descends to and has a pressure of .The upper photic zone of the ocean is filled with particle organic matter (POM) and is quite productive, especially in the coastal areas and the upwelling areas.