The mantle is not molten at 25 miles depth. The pressure keeps it solid. Also, molten material under the surface is referred to as magma; lava is the word used for magma that has erupted onto the surface via a volcanic vent.
EarEarth’s outer core is a fluid layer about 2,260 km (1,400 mi) thick, composed of mostly iron and nickel that lies above Earth’s solid inner core.
The inner core’s intense pressure—the entire rest of the planet—prevents the iron from melting. The pressure and density are simply too great for the iron atoms to move into a liquid state.Jun 11, 2024