I found it interesting that in order for the earth to have an high concentration of Oxygen in the atmosphere, Carbon needs to be extracted from the surface of the earth and buried. The major generation of Oxygen took place in two phases. The first starting 750 million years ago based on ocean phytoplankton and the last phase when plant live spread to land. In both cases the death and deep burial of the carbon contained in these organisms unbalanced the O2 chemistry such that excess O2 was left in the atmosphere since there was no carbon to burn with. Cool.
Nearly all the carbon on earth is stored in rocks as a result of those and other processes. See table 1 here: Carbon cycle - Encyclopedia of Earth The table shows all known fossil fuel deposits as containing 4,000 billion tons of carbon, versus all carbonate rocks as containing 100,000,000 billion tons of carbon. There are several carbon sequestration proposals that amount to increasing the weathering of rocks that can capture carbon as they weather. The cheapest ones amount to taking selected mine and quarry trailings and spreading them out rather than piling them up. Basically speeding up the production of carbonate from rock weathering. Here are a few examples: Carbon sequestration through accelerated weathering of mining and quarry waste — University of Leicester Carbon Sequestration - Turn Carbon Dioxide Into Rock - Popular Mechanics Scientists Enhance Mother Nature's Carbon Handling Mechanism It's not clear that these would necessarily work as planned. And its clear that it would take vast amounts of rock to make much of a dent in carbon emissions. But the basic idea for these is to take rocks that will produce carbonate when exposed to atmospheric C02, and increase the rate of exposure.
There is a new report out that says the melting ice caps are releasing iron and the algae in the ocean feed on that then absorb CO2 and when they die they trap it on the ocean bottom so the melting ice caps have a negative feedback.
http://www.geocraft.com/WVFossils/Reference_Docs/Geocarb_III-Berner.pdf is a fundamental reference on CO2 history, so well as it is known. Note that CO2 'trapping' by silicate weathering does not liberate O2, while an excess of photosynthesis over decomposition does.
Well, if we want to be technical, THE first major generation of oxygen occurred 3.5 Billion years ago, when the earths atmosphere consisted of almost entirely CO2 and water vapor (when water vapor first arrived on earth, the formerly-molten earth was still too hot for water to precipitate to liquid. As the earth cooled, that vapor precipitated.), the stromatolites photosynthesized billions of tons of CO2 into O2. One of the waste products of Stromatolites (which can still be found alive and studied today in Shark Bay, Australia), is actually rock. Using the common geological method for dating the age of rocks by comparing the ratio of uranium to lead (trapped in trace amounts in rock all around the earth, all throughout the geological record), billions of formations of rock created by stromatolites have been dated back to 3.5 Billion years ago. This also indicates that there was water and primitive life 3.5 Billion years ago. (SOURCE: "How the Earth Was Made," The History Channel DVD, ISBN: 1-4229-0902-6) THIS IS ONE OF THE MOST AWESOME DVDs I HAVE EVER PURCHASED AND I HIGHLY HIGHLY HIGHLY RECOMMEND IT !!!!!!! (It explains HOW geologists know that the earth is 4.5 Billion years old, and it explains HOW geologists know the history of the earth and HOW they know everything we know about plate tectonics, sea floor spreading, the earths crust, mantle, and so on and so forth. It's fascinating!) :welcome: Back on the subject of CO2, I saw a program on The Science Channel tonight of some entrepreneur's vision that all CO2 produced from industrial and power plant emissions will be captured, condensed to liquid and injected into the earth where empty pockets exist from natural gas extraction. He estimated it will take 30% more energy to capture, compress, and rebury the CO2, but if we just abandon the hydrocarbons, we get nothing. We might as well benefit from the energy if we can bury the CO2. So they are currently experimenting with [safe] burial of CO2 (their argument is that the methane that was trapped down there for millions of years never escaped, so why should the CO2. It's a valid argument). It's interesting. Millions of years from now, earthquakes will disturb the deposits and they will fill the atmosphere with CO2 ... but humans will likely be long gone by then - not because we destroyed ourselves, but because the earth's history has been packed with cataclysmic events. We are VERY fortunate to be living in a calm, peaceful few thousand years of earth's history. It's normally not like this.
Around 2.7 billion years ago, there was enough O2 accumulated in the atmosphere that banded iron formations were no longer able to form, for what that's worth.
The original article made some points I did not elaborate on: 1) The first O2 appearance was 2.2 billion years ago with very small percentages, too small to support O2 based life. (Just repeating the article, do not know why the discord with 3.5 billion.) 2) The O2 was liberated when biological organic sedimentation was swallowed up by subducting plates carrying the carbon to the mantle with very little of this converted to oil or coal. 3) The amount of energy expended (and presently stored) in our O2 is "2e10 TeraJoules hydrogen bomb equivalents". All of it from solar energy.
