Slow-motion collisions of tectonic plates under the ocean drag about three times more water down into the deep Earth than previously estimated, according to a first-of-its-kind seismic study that spans the Mariana Trench, a crescent-shaped trench in the Western Pacific that measures 1,500 miles long and is the deepest ocean trench in the world. The observations from the trench have important implications for the global water cycle, according to researchers at Washington University in St. Louis whose work is supported by the National Science Foundation. Researchers listened to more than a year's worth of Earth's rumblings, from ambient noise to actual earthquakes, using a network of 19 ocean-bottom seismographs deployed across the Mariana Trench, along with seven island-based seismographs. The Mariana Trench is where the western Pacific Ocean plate slides beneath the Mariana Plate and sinks deep into the Earth's mantle as the plates slowly converge. The new seismic observations paint a more detailed picture of the Pacific Plate bending into the trench, resolving its 3D structure and tracking the relative speeds of types of rock that have different capabilities for holding water.
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