"Rock from the upper mantle slowly rises to fill the void between the plates, melting as the pressure decreases, then cooling and re-solidifying to form new crust along the ocean bottom. read more
The oceans are not in the Earth’s mantle, they are on the earth’s crust. There are a few places on the ocean floor where fault lines occur where mantle seeps out, the ocean water gets very hot and boils. read more
Earth's mantle is a silicate rocky shell with an average thickness of 2,886 kilometres (1,793 mi). The mantle makes up about 84% of Earth's volume. It is predominantly solid but in geological time it behaves as a viscous fluid. The mantle encloses the hot core rich in iron and nickel, which makes up about 15% of Earth's volume. read more
Temperature in the mantle The upper mantle has a temperature range between 500 degrees and 900 degrees Celsius near the crust. Deep in the Earth at the boundary with the Earth's core the rock temperature is about 4000 degrees Celsius. read more