Through the process of ? , old , dense crust is pushed toward a deep-ocean ? there, it’s sinks under lighter crust. it returns to molten rock, becoming part of the ? again

The correct answers are:

- subduction;

- trench;

- mantle;

The tectonic plates are constantly moving around the planet, though that is not noticeable with bear eye. Some plates are moving away from one another, some slide past each other, and some collide. Where we have plates that collide, we have a subduction zone. This means that the plate that is heavier, denser, gets under the lighter, less dense plate. As it moves bellow it, cracks are made in the crust between them, resulting in the formation of deep-ocean trenches. As one of the plates goes bellow the other, little by little the crust is becoming molten rock again, thus becoming part of the mantle layer again. The chances are also high that the crust that got into molten rock can appear on the surface again, forming new crust.