Geology - A Closer Look

Hi Guys,

Starting this new series of blogs, we are going to be taking a closer look at geology... more specifically, different types of rocks and minerals and what they are made of.

So what better place to start than the formation of the Universe!

According to the most widely held theory of how the Universe came into being, the physical Universe and all within it emerged from an infinitely small point of pure energy in a highly compressed state and at an extremely high temperature. The rapid expansion of this point of energy through the Big Bang resulted in a relatively rapid drop in its density and temperature, and within a few seconds a number of elementary particles formed, such as electrons, photons, neutrons and protons. (Protons and neutrons are themselves made of Quarks. One " down" and two "up" quarks made a proton, while one "up" and two "down" quarks made a neutron). Between 1 and 180 seconds after the Big Bang, collisions between protons and neutrons formed the nuclei of light elements, mainly helium, though they did not yet capture electrons.

This expanding mass of energy and particles was still far too hot for the formation of atoms (made from the binding of electrons, protons and neutrons), and it would require another 500,000 years of expansion and cooling before the first atoms appeared, mainly of hydrogen and helium. This was possible due to helium nuclei capturing pairs of electrons, forming helium atoms, while protons captured one electron each, forming hydrogen atoms.

Hydrogen and helium gas, along with two other light elements, lithium and beryllium, were the only chemical elements in the Universe for millions of years. Eventually, variations in the density of matter in the expanding universe caused small regions of higher gravity to occur, ( the denser matter becomes, the more gravitational force it exerts). Gas was drawn into these regions by the force of gravity, creating vast coalescing clouds of hydrogen. Within each of these huge gas clouds, (called nebulae), numerous even more dense areas formed, each drawing yet more gas into itself. Eventually, in the centres of the densest areas of gas, temperatures and pressures rose to such a point that hydrogen atoms began to fuse together to form helium. This nuclear fusion generated light and yet more heat, creating the first stars to light the newly formed Universe. Each cloud of newborn stars constituted a galaxy.

Stars can be thought of as factories for making heavier elements from hydrogen. At the high temperatures and pressures at the cores of stars, nuclei can collide with such energy that they fuse together to become heavier elements. These heavier elements can then fuse with more hydrogen or with other freshly made nuclei to form heavier nuclei. In this way, oxygen, carbon, and most of the other elements up to the the mass of iron are formed.

Heavier elements than iron are made towards the end of the life of large stars by a process of adding neutrons to nuclei and radioactive decay. At the end of the life of large stars, the star will explode. Such an explosion is called a supernova. Minerals are found in meteorites that formed around supernovae.

New stars are created from material spread through space by the explosion of other stars. Our own star, the Sun, is a third generation star, containing elements that have been cycled through at least two other stages of star death. Although, like all stars, second generation stars are mainly hydrogen, they incorporate elements formed in the first generation of stars and can use these as building blocks for new isotopes and elements. (Isotopes are just variations of the same element, e.g carbon, with a different number of neutrons.) We can identify these second - generation elements and isotopes in the sun and in the planets circling it, including the earth. (Source: Rocks and Minerals by DK Publishing. Photo courtesy of Google Images).

Next week we will look at the birth of our sun, and the origin of our planets, so stay tuned!