The Abyssal plains are my answer.
Answer: Most of the world's volcanoes are found around the edges of tectonic plates, both on land and in the oceans. On land, volcanoes form when one tectonic plate moves under another. Usually a thin, heavy oceanic plate subducts, or moves under, a thicker continental plate.
Approximately 97.5% of the earths water is salt water (saline), and 2.5% is fresh water hope this helps.
