Plate Tectonics

What is a deep mantle?



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Earth's mantle is a rocky shell about 2,890 km (1,800 mi) thick that constitutes about 84 percent of Earth's volume. Two main zones are distinguished in the upper mantle: the inner asthenosphere composed of flowing rock in the state of plasticity, about 200 km thick, and the lowermost part of the lithosphere, composed of rigid rock, about 50 to 120 km thick. A thin crust, the upper part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick. The mantle is divided into sections which are based upon results from seismology. These layers (and their depths) are the following: the upper mantle (starting at the Moho, or base of the crust around 7 to 35 km, downward to 410 km), the transition zone (410-660 km), the lower mantle (660-2891 km), and in the bottom of the latter region there is the anomalous D" layer with a variable thickness (on average ~200 km thick)