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From swamp forests to coal

300 million years – 300 metres

Giant dragonfly Meganeura in a Carboniferous forest. (Walter Myers)

Climate is cooling due to the movements of continents and decreasing carbon dioxide bound by swamp forests. Glaciations cause large fluctuations in sea level and tens of metres tall fern forests form the majority of the Earth’s present coal deposits. Amphibians diversify and first reptiles evolve. Most of the current insect groups develope and the Meganeura dragonfly hase a wingspan of over 70 cm. Finland is in the tropics.

Photo: Meganeura giant dragonfly at Carboniferous forest. Walter Myers

Carboniferous period

The flora of the carboniferous period was very versatile, mostly swamp vegetation. Tens of meters tall fern forests were prevalent at tropical regions. Also the first seed plants had evolved already in the Devonian and started to became more common at Carboniferous.
Hannes Grobe / Wikimedia

Movement of Gondwana-continent toward southern polar regions and drastic drop in atmospheric carbon dioxide resulted wide glaciations. Image: Hannes Grobe, Wikimedia

Swamp forests bound effectivly carbon dioxide and released oxygen. Cooling climate and movement of Gondwana-continent toward southern polar regions triggered glaciations. Constant glaciation, and their cyclic growth and reduction cause large fluctuations in sea level. In the tropical regions the swamp forests were repeatedly destroyed and buried within the raising waters, and thus form the majority of the Earth’s present coal deposits. Due to the fluctuating pattern, the coal deposits were formed in repeating layers, each a few meters thick with intervening layers of sand and clay in between.

Amphibians and insects diversified and dominated the terrestrial life. The first reptiles evolved. They were small lizard-like insectivores. The high oxygen levels allowed the appearance of giant insects and amphibians, for example the Meganeura-dragonfly had a wingspan of over 70 cm and millipede Arthropleura grow over 2 m long. Life was also rich and versatile in all different waters.

Flora and fauna in Carboniferous swampforest, including giant amphibians. Swampforests can bind carbon dioxide effectively. Image: Walter Myers