Where are deep ocean trenches formed?

Deep-Ocean Trenches are actually formed at a convergent plate boundary where an oceanic plate and a continental plate collides. These trenches are the ocean's deepest floor. These are position paralleled to the volcanic arcs. A great example of this is the Mariana Trench in the South Pacific Ocean.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.