Thousand dollar question they hope the trenches shallower western edge my provide the answer here they found an intriguing chain underwater Hills two miles below the surface of the sea the movie engineers drill down into the hills and collected core samples and when the scientists analyzed the samples they discovered the hills ht rush were actually volcanoes and they spewed out not lover but mild the fine powdery mud is made up for the soft type of rock that has been ground up in thesubduction zones it seemed the soft rock might explain why there have been no major earthquakes at the Marianas.

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