Gary sent in this link to www.dailymail.co.uk/sciencetech/article-4895642/Crust-change-billions-ye… … changesin Earth's crust 2.4 billion years ago increased oxygen levels in the atmosphere and triggered an explosion of life. Oxygen increased 10,000 times over within a period of 200 million years (or that is the estimate in uniformitarian time scales). It sounds like that might need modifying.
We are told Earth's early atmosphere was devoid of free oxygen even though cyanobacteria were making the gas as a by-product of photosynthesis. Free oxygen is oxygen that isn't combined with other elements such as carbon or nitrogen and aerobic organisms require it in order to live and thrive. Around 3 billion years ago small regions of free oxygen popped up in the oceans – and at 2.4 billion years ago oxygen suddenly increased in the atmosphere. This s known as the Great Oxidation Event and it changed chemical reactions on the surface of the Earth. Even the components of the continents change. Prior to this event rocks were rich in magnesium but low in silica, and these rocks dominated the continents. As an example of such rocks they say they can still be found in Iceland and the Faeroes – new continental crust outcrops (as a result of tectonic activity). These rocks also contain olivine and when olivine comes into contact with water it produces a chemical reaction that consumes oxygen – and locks it down. The theory is that this is what happened to the oxygen produced by the cyanobacteria – inhibiting its growth. The next step in the chain is that the rocks evolved – becoming more like they are today. Quite how rocks evolve as they are not alive is anyone's guess – but evolve they did (according to the theory). The theory then goes on to say that as olivine became less important as a feature of rocks cynobacteria was able to produce oxygen that stayed around (which I suppose involves a certain amount of modelling). Oxygen gradually built up – but it would in a gradualist uniformitarian model. Here then is why they say it took 200 million years to get lots of oxygen in the atmosphere. It is an arbitrary number that fits into geochronological time scales. It is much more likely that the Great Oxidation was a rapid event – and therefore cyanobacteria was not the source. The fact it coincided with big changes in continental rock formations (or their evolving structure) tells us that catastrophism was at play. The Mantle is rich in silica, for example, and water. Tectonic forces may have been at work as Plate Tectonics are thought to have been initiated at the same time. All we can really take from this research is the sudden appearance of oxygen which opened the way for life as it developed.
At https://archaeologynewsnetwork.blogspot.co.uk/2017/09/scientists-produce… …. we learn the four most abundant elements, iron. oxygen, silicon and magnesium together make up more than 90 per cent of the Earth's mass.