Why does the Mariana Trench exist?
What’s the explanation of this remarkable crevasse in the earth’s skin? Plate tectonics! The skin of the earth consists of separate plates that move relative to each other. Plates are formed at ocean ridges and consumed at trenches. The Mariana Islands owe their origin to subduction, the process of thrusting one plate under another. The Mariana Trench is the location where the Pacific Plate ducks steeply under the Philippine Plate. Cross section: converging plates on the left and diverging plates on the right. Plate tectonics is all about plate boundaries. There are three kinds of plate boundaries: • spreading centers and ridges, where plates separate (diverging plates); • trenches, where plates collide and where one ends up ducking under the other (converging plates) …and where mountain chains can form (the Himalayas are the result of two plates bumping into each other); • faults such as the San Andreas, where plates slide past each other laterally. Earthquakes occur where plates sl
