This is the biosphere. The Interior of Earth Use earthquakes to probe structure of interior. Lithosphere which is cool and rigid and about 100 km. thick Mantle below the lithosphere that is warmer and partially molten. Where magma for volcanic eruptions comes from. The deepest layers of the mantle are under such high pressure, the rock is solid in spite of being hot.
Convection carries heat from the mantle to the bottom of the lithosphere.
The core is metallic, with the outer layer being molten but the very center being solid due to high pressure. None from 4 billion years ago, so they were erased by other processes. Erosion got rid of most of the craters and changes the Earth's surface in many ways. Mostly due to water, some due to wind. Erosion is more important on Earth than on the other planets.