Carboniferous

During the Carboniferous, Earth’s landmasses were clustered around the equator, forming tropical and subtropical swamp forests. These forests were dominated by giant ferns, horsetails, and lycophytes, which eventually became the coal deposits we mine today. The oxygen concentration in the atmosphere reached as high as 35%, far higher than today, supporting the growth of massive insects, such as Meganeura (a dragonfly-like insect with a wingspan of over two feet).

Amphibians, which first evolved in the Devonian, diversified significantly during the Carboniferous, adapting to both aquatic and terrestrial habitats. The first reptiles appeared in the Pennsylvanian subperiod, marking a major evolutionary milestone, as reptiles were better adapted to dry conditions than amphibians. This adaptation likely gave them a significant advantage in environments farther from water sources.

Geologically, the Carboniferous saw the assembly of the supercontinent Pangaea, bringing together most of Earth’s landmasses. The movement of Gondwana toward the South Pole triggered glaciation events, particularly toward the end of the Carboniferous, which would continue into the Permian period. These glaciations, combined with tectonic activity, created a fluctuating climate that impacted sea levels and marine life.

The rich, dense forests of the Carboniferous provided the organic material that would later form vast coal deposits. The period’s name, “Carboniferous,” literally means “coal-bearing,” reflecting the widespread formation of coal beds during this time.