Slabs of ocean floor return to the mantle in subduction zones.Description<span>
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In Russia, after the global financial crisis in 1998, Russia became a major exporter of grain after 2001.
Earth is composed of four main layers, starting with an inner core at the planet's center, enveloped by the outer core, mantle, and crust. The inner core is a solid sphere made of iron and nickel metals about 759 miles (1,221 kilometers) in radius.
source: nasa