How can we be so sure that the Marianas Trench is the deepest place on Earth when much of the ocean hasn’t been explored yet?

Question

How can we be so sure that the Marianas Trench is the deepest place on Earth when much of the ocean hasn’t been explored yet?

In: Geology

Answer 1

The study of geology and plate tectonics gives us a general understanding of why places are deeper than others. The pacific plate, a dense flat basalt, is colliding with and going underneath (subduction) the Eurasian plate, with is much more “buoyant.” Every subduction zone where these collisions occur results in deep trenches and high mountain ranges.

So because of that, we know the deepest spots are likely to be off the coast of Asia/Oceania, the west coast of North America, or the west coast of South America (I am probably missing a few but you get the point).

With that known, satellites and other vessels can do further mapping of the areas and don’t have to scour the entire ocean for the deepest part. We know the dense basalt will be flat, and subducts beneath the buoyant continental crust.