The Mariana Trench is the deepest natural point in the world, located in the western Pacific Ocean approximately 200 kilometers (124 mi) east of the Mariana Islands. It is thought to be a subduction zone where the seafloor of the Pacific is gobbled up by the continental plate to the west. It must therefore have come as a surprise to researchers that this zone draws in water at an enormous rate.
Subduction implies a reduction of seafloor area. The quantity of water in a subduction zone should therefore go down. It should push water out to the sides as seafloor is gobbled up. Alternatively, subduction trenches must grow deeper at a rate that exceeds the volume lost by the shrinking seafloor. Since the Mriana Trench is not growing deeper at the required rate, and water is nevertheless rushing in towards it, the explanation must be that subduction is not in fact happening, or there are drains at the bottom of the trench, forcing water into the Earth.
Unwilling to give up on the idea of subduction, and unable to find holes for water to drain into, geologists have come to the conclusion that water is somehow mixed with the rocks that are subducted in under the continental plate to the west. This would mean that the rocks that sink into the Earth are of very low density, making the whole subduction story all the more fantastic. Nowhere in physics do we see low density materials sink in under denser materials. But in geology, this is supposed to happen at an extraordinary rate.
A more logical conclusion would be that the Mariana Trench is not in fact a subduction zone but an expansion rift. An expanding seafloor at the trench, even if expanding at a very slow pace, would require huge amounts of water to fill the the volume created.
South pole view of the expanding Earth
What the geologists have discovered is not another fantastic mechanism of subduction where water gets gobbled up by Earth’s crust, but further proof that Earth is expanding.