Running Out of carbon Dioxide.
The oceans nearly absorbed all carbon dioxide from the air 300 million years ago. In the nick of time, volcanoes replaced some of it, but they died down, and now the CO2 is almost gone again.
There was five times as much CO2 in the air during dinosaur years, and twenty times as much when modern photosynthesis began. All biology is on the verge of becoming extinct due to a shortage of carbon dioxide in the air which is necessary for photosynthesis.
The oceans constantly absorb CO2, as it combines with calcium to form calcium carbonate and limestone. The result was almost total depletion of CO2 from the atmosphere 325 million years ago. Then a significant restoration of CO2 in the atmosphere occurred. Volcanoes would have been the source of the increase.
There were no volcanoes during the critical decline in atmospheric CO2. Tectonic plates were moderately thick preventing volcanoes from occurring. As tectonic plates collided, they would form small mountains but nothing drastic enough to create volcanoes. As the plates got thicker due to constant cooling of the earth, mountains got larger and volcanoes appeared restoring CO2 to the atmosphere.
Then CO2 levels began to decline again during the dinosaur years. The decrease would have been a result of tectonic plates getting so thick that volcanic magma could not easily get to the surface. Yet, oceans continue to absorb CO2 and convert it into calcium carbonate and limestone.
Now, the amount of CO2 in the atmosphere has been leveling off, and human acticity is said to be increasing the amount of CO2 in the atmosphere. Is there some other force causing the reduction in CO2 to level off besides human activity? Perhaps the oceans cannot absorb more CO2 at extremely low levels.
The high level of CO2 500 million years ago may be due to high volcanic activity with thin tectonic plates. As the plates got thicker, lava could not get to the surface as easily. If so, there were two periods of high volcanic activity—the first due to thin tectonic plates, and the second due to plates going over and under each other.