How the Earth formed its core – Science News, July 1, 1972
At first, scientists thought there were interstellar gas clouds of all the elements that make up Earth. About a billion years later, Earth is a sphere of concentric spheres with a solid iron inner core, a liquid iron outer core, and a liquid silicate mantle… The current theory is that the primordial cloud material accreted…and was accreting Sometime later, the radioactively heated and melted iron sank toward the center of the Earth…. Now another concept is in vogue: The Earth may have accreted… core formation and accretion occur simultaneously.
Most scientists now agree that the cores formed as the material that makes up Earth collide and clump together, and that this process is driven by the heat from the smashing. Earth’s heart is mostly made up of iron, nickel and some oxygen, but what other elements might be in it and in what form remains an open question.Recently, scientists have proposed The inner core may be superionicliquid hydrogen flows through the iron and silicon lattices (SN: 3/12/22, 12th).