The high degree of carbon in the atmosphere afforded the new land varieties of life opportunity for speedy and luxuriant growth. [1]
950,000,000 years ago the atmosphere was clearing up, but the amount of carbon dioxide continued large. 220,000,000 years ago the land was overrun by luxurious vegetation; this was indeed the age of ferns. Carbon dioxide was still present in the atmosphere but in lessening degree. [2]
Much of the carbon of the atmosphere was abstracted to form the carbonates of the various metals which abounded in the superficial layers of the planet. [3]