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Iron Ore Deposits
Eventually,
photosynthesis by the earliest forms of
plant life (a form of life capable of feeding itself instead of feeding off of others) began to produce significant amounts of oxygen. One important thing to know about oxygen is that it likes to attack other
elements and attach itself to them. Iron, in particular, is easily attacked by oxygen.
Other forms of heterotrophic early life (life forms which eat things outside themselves) had been producing waste products such as iron, which built up in the early ocean. As oxygen began to be produced, a peculiar thing happened. Large amounts of iron which had accumulated in the early ocean were attacked by the accumulating oxygen. When oxygen reacts with iron, iron ores are produced. Today, iron ores are taken out of the ground by miners, and the iron they contain is used by human beings to make lots of things.
For a billion years, the oxygen produced by early plant life attacked leftover iron in the ocean, and huge deposits of iron ores were laid down at the bottom of the sea. This activity took place between 3.5 and 2.5 billion years ago. Iron ores mined today in the United States, Australia, and South Africa, are part of the huge deposits laid down at that time. Once the oceans were swept clean of iron, then the oxygen could begin to build up in the atmosphere, and respiration
by sophisticated life forms could begin in earnest. It took a billion years for this process to complete. When it was finished, it closed the period in the history of the Earth which we call the Archean
.
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