Which layers of the earth are solid and which are liquid?
The crust and the inner core are solid, whereas the outer core and inner mantle are liquid. The outer mantle is semi solid.
The inner core is solid due to the massive pressure on it. Scientists theorize that the heat of the solid inner core is keeping the outer core in a semi-liquid state which allows the inner core to spin at a slightly different rate than the rest of the earth. This gives the earth its magnetic poles which diverts damaging cosmic rays from colliding with earth. The theories are the result of measurements during volcanic activity and sound waves.
The mantle is a plastic solid of varying densities which allow convection currents to flow molten rock towards the earth's surface resulting in volcanic activity, tectonic plate movement, earthquakes, and movement of continents.
There are a lot of drawings here:
The formation of the solar system is here: