Hello, back again, as explained in the last post we shall now be looking in lit bit more detail as to what happened in these periods that make up the eras. As we get closer to 2012, we find that more has been found and purported to be found, so there will be more to say. I shall endeavour to be as concise as possible. I will only try to add what I think is pertinent to the evolution of both Whatlington and Vinehall Street.
The Siderian Age ran from 2,500 to 2,300 million years ago and oxygen was produced as a waste product by anaerobic (without oxygen) algae (as previously mentioned here); this had an effect on the previously formed iron by creating an iron oxide, later named magnetite (Fe3O4) and is known for its magnetic properties. This had the side effects of taking iron out of the sea water, which previously had a greenish colour and was now a lot clearer, as well as creating a more oxygen-rich atmosphere. There are still examples of the banded iron formations, which were created in this age, in the sediments of Minnesota, USA. For those that know Whatlington and Vinehall Street in Sussex may well be aware that the early development of these two villages did rely on the iron resources.
It was during this period that continents began to show above the waters on the planet. But all was not well, especially above the planet's surface. This abundance of oxygen in the atmosphere created an event that was later known as the oxygen catastrophe. Before this event, organic matter, such as the aforementioned algae and dissolved iron, would capture any free oxygen.
But after the event, the rising saturation of free oxygen in the atmosphere led to the deaths, on a planet wide scale, of anaerobic life. It also oxidised methane (CH4) to create a weaker greenhouse gas carbon dioxide (CO2) and water (H2O). Like a line of dominoes, one change can lead to a lot of other changes or, as we like to call them on Earth, catastrophes.
Catastrophe One - The Huronian Glaciation - the water in the atmosphere led to one of the longest and most severe glaciation events, which lasted from 300 to 400 million years covering both the Siderian and Rhyacian periods. It could be said that this glaciation may have also started from a decrease in volcanic activity and the angle of tilt in the earth.
Catastrophe Two - Increase in Biological Diversity - the abundance of free oxygen in the atmosphere led to opportunities in the chemical reactions between substrates and the Earth's atmosphere, oceans and surface's fresh water. The energy (in the form of adenosine triphosphate or ATP) created within cells, known as mitochondria, are thought to have formed after the Oxygenation Catastrophe.
Catastrophe Three - Increase in Mineral Diversity - it is thought the Oxygenation Catastrophe is responsible for creating 2,500 new minerals from the 4,400 known minerals found on Earth by the processes of hydrating and oxidising. There are still some minerals to be discovered, but an article by Robert M. Hazen in the Scientific American journal:
"Most of these new minerals occurred as thin coatings and rinds of altered material on existing rocks. Many rare mineral species are known from only a handful of precious crystals that weigh less than a gram. But the Great Oxidation Event" or the Oxidation Catastrophe "had global mineralogical consequences as well. Most notably, the planet rusted - across the globe, the black basalt...turned red as the ferrous iron of common basalt mineral oxidised to hematite and other rust red ferric iron compounds". Scientific American March 2010 (Accessed 17/12/2011 - http://www.scientificamerican.com/article.cfm?id=evolution-of-minerals&page=1)
Next time: The Rhyacian Period
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