what boundary do trenches form?
<answer> Trenches define one of the most important natural boundaries on the Earth’s solid surface, that between two lithospheric plates. <context> Oceanic trench. The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They also are the deepest parts of the ocean floor. Trenches define one of the most important natural boundaries on the Earth’s solid surface, that between two lithospheric plates.