10 Deepest Parts of the Ocean - Marine Insight — The deep holes in the Mariana trench were formed due to the collision of converging plates of oceanic lithosphere. During the collision, one plate descends into the mantle and the downward flexure forms a trough at the line of contact between the plates.
Southern Ocean - Wikipedia — "Southern Ocean" is an obsolete name for the Pacific Ocean or South Pacific, coined by Vasco Núñez de Balboa, the first European to discover it, who approached it from the north. The "South Seas" is a less archaic synonym. A 1745 British Act of Parliament established a prize for discovering a Northwest Passage to "the Western and Southern Ocean of America".