What occurs at underwater subduction zones

At underwater subduction zones,the oceanic and continential plate collides into one another. The denser plate would be subducted unsder the less dense plate.

At the subduction zones,submarine volcanoes or volcanoes would form as magma rise along the crack.
Under subduction,ocean trench would also be formed.
If it is an continential plate and oceanic plate subduction,fold mountain may be found.

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Answer

TrenchesExplanation

A subduction zone is the largest wreck scene on Earth. These lines indicate the crash within two of the planet's tectonic plates. The plates are pieces of crust that slowly move across the planet's cover over millions of years. Where two tectonic plates meet, if one or both of the plates are oceanic lithosphere, a subduction zone will form. An oceanic plate will soak back into the mantle. Remember, oceanic plates are made from mantle material at midocean ranges.

South wales composes a lot of coal in that region.

Answer decreased soil salinity;