The Third atmosphere was a rearrangement of the plate tectonics and the evolution of atmosphere by the transferring of it to the oceanic basins. As the amount of oxygen in the atmosphere used to be more than 30% around 280 million years ago than the present.
Rapid development of land plants and animals was caused due to this atmosphere and hence this atmosphere is now less than 21% and due to his influence or modification of man with his technological tools and techniques.
The atmosphere is rapidly shrinking due to the greenhouse effect and global warming that is leading to the fifth atmosphere that may be like that of mars as devoid of gases and barren and dry with oceans running under the crust.
I believe the plates are called the south American plates just saying I might be correct or I might be wrong so don't take my word for it I am not the expert
