How Rocks Originated

Sham S. Misri

Nearly 4.5 billion years ago the earth was a ball of molten magma. The magma was made of 92 elements. Elements are made of atoms. Atoms have nuclei of protons and neutrons, with electrons spinning around them. Each of the naturally occurring 92 elements has a different number of electrons and protons in its atoms. The simplest and lightest element is hydrogen. It has one proton in its nucleus, and one electron orbiting its nucleus. If another proton and electron are added to a hydrogen atom, another different element called Helium is formed. The more electrons and protons are added to the atoms of an element, the heavier that element becomes.

99 % of the mass of universe is made up of only two elements: Hydrogen and Helium. Ninety nine percent of the earth however, is made of eight elements: Iron, Oxygen, Silicon, Magnesium, Sulphur, Nickel, Calcium and Aluminium. The mystery as to why there are so many heavy elements on the earth and   only two main light elements in the universe can be explained by understanding how elements are formed in space.

Some places in the universe have high concentrations of hydrogen that are very hot. When hydrogen reaches the temperature of ten million Kelvin, two atoms of Hydrogen can combine to form one atom of Helium. When this happens, free neutrons from the nucleus of Hydrogen atoms are released as energy, causing more heat. This in turn causes more Hydrogen atoms to fuse together to form helium. When nuclear fusion is taking place this quickly in a cloud of hydrogen in space, so much energy is released that a star is born.

As long as a star is burning, nuclear reactions are taking place deep within the star. Not only are helium atoms being formed by nuclear fusion, but other, heavier elements are being formed as well. Elements are synthesized inside stars!

Sometimes nuclear reactions inside a star become so intense and uncontrollable that the star explodes like a gigantic bomb. This phenomenon is known as supernova. When a supernova explodes, atoms of elements the star has synthesised go into space, making new stars and sometimes planets can be born.

Sometimes shooting stars or meteors are seen at night. Some meteors are big enough that they make it through the Earth’s atmosphere without burning up. When they hit the earth they are called the meteorites.

It took millions of years for the molten magma to cool. Patches of thin crust were formed on the surface of the magma ocean. Combinations of different elements were cooling together, forming the very first rocks of the Earth’s crust. The very first rocks on the Earth were igneous-meaning ‘from a fire’.