[maxmalkav]

> Basically plants evolved Lignin (wood) but there was nothing in the world that could break it down so it rapidly accumulated along with a hyperoxgenated atmosphere due to the extensive growth.

That was my understanding too until recently, when I have read in a couple of places that things might not have been like that. Checking the Wikipedia article about Carboniferous [1] it seems there is not consensus yet:

"There is ongoing debate as to why this peak in the formation of Earth's coal deposits occurred during the Carboniferous. The first theory, known as the delayed fungal evolution hypothesis, is that a delay between the development of trees with the wood fibre lignin and the subsequent evolution of lignin-degrading fungi gave a period of time where vast amounts of lignin-based organic material could accumulate. Genetic analysis of basidiomycete fungi, which have enzymes capable of breaking down lignin, supports this theory by suggesting this fungi evolved in the Permian. However, significant Mesozoic and Cenozoic coal deposits formed after lignin-digesting fungi had become well established, and fungal degradation of lignin may have already evolved by the end of the Devonian, even if the specific enzymes used by basidiomycetes had not. The second theory is that the geographical setting and climate of the Carboniferous were unique in Earth's history: the co-occurrence of the position of the continents across the humid equatorial zone, high biological productivity, and the low-lying, water-logged and slowly subsiding sedimentary basins that allowed the thick accumulation of peat were sufficient to account for the peak in coal formation."

One way or another, I find fascinating how different the planet has been along its geologic periods.

[1] https://en.wikipedia.org/wiki/Carboniferous#Coal_formation