It's almost impossible to know the precise ways in which the core of the earth was formed but technology give us many clues. Many unanswered questions remain about what is at the center of the earth and what holds it together. While the question is a logical one asked almost as frequently as the one asked of parents by curious youngsters, where did I come from, the answers vary.
Depending on the audience: academic and attuned to physical science with lots of serious star gazers present; religious oriented folk with various educational levels that seek to prove or to disprove the existence of a benevolent God; high school science lectures, etc., a researcher has no easy time when providing answers. When more definitive answers are found, they, when coming into contact with those long held will be met with skepticism.
Yet when proof is shown and more answers are asked, most will agree that’s it impossible to know for a certainty how the core of the earth was formed. For proof of that look no further than Pluto, once making up the ninth planet, being declassified as a planet. The earth is changeable and the only certainty about it is uncertainty.
How then did the earth form? “The Earth formed through accretion, absorbing planetisimals (lumps of rock and ice) through collisions.” Broken down into easily digestible particulates, that means certain forms clumped together and those more attracted to each other clung together. The outside given time would become somewhat hardened by weathering the other atmospheric conditions and the more perishable would be forced to gravitate to the interior for protection from the elements. The of the earth is Iron and nickel since these are heavy and are necessary for growing the rest of the earth. These came from meteorites—asteroids and comets—that fell from some type of explosion and a new form began.
In fact science explains the whole universe and the formation of the other planets by this same process. The difference in composition is explained in their varying weathering conditions. Heat was needed to melt the nickel and force it to flow into the interior of earth and a cooling condition hardened it.
An easier way of getting a mental picture of how the earth forms and decays and reforms is to picture it as the human body. The body, in essence, is a living form of matter that at death becomes inert and goes back to form part of the earth. Iron is necessary in the human body, without it there wouldn’t be any red blood cells. A body without any iron will not live since it is the primary means of oxygen transmission. Too much iron is toxic and works the body. Iron also has as yet unexplained suppressing qualities to nickel in the body. The function of nickel in the body is not clear, but nickel allergy is common.
And no matter how studying does, eventually they run into brick walls when attempting to explain adequately how the earth’s core is formed or how a human being is exactly—DNA and all—put together. Suffice it to say that the earth is a rotating form of matter made up of varying substances, positive and negative in reaction and is subject to eruption from time to time. So are humans.
Various conditions affect the earth that cause the wind to blow too rapidly; water to overflow; the underlying plates to collide and break apart causing earth quakes; too much heat causing rising water levels—melting glaciers— and any number of other catastrophic events that change the face of the earth, also can be seen in human beings. Temper tantrums, edema, broken bones, high blood pressure and allergies, to name only a few offer an analogy of the human and earth conditions. Each action has an equivalent reaction in the other; that much we know for certainty about how the core of the earth was formed.