The Earth is a part of the solar system and it has been influenced by its elements since ... ~ Plasticity in the Mantle ~ - Layers of the EarthMagma: Molten (Melted) Rock that is UNDERGROUND. Lava: Molten (Melted) Magma that has Reached the SURFACE of the Earth Inside the Earth [This Dynamic Earth , USGS]Inside the Earth The size of the Earth -- about 12,750 kilometers (km) in diameter-was known b