The Carboniferous Period

The Carboniferous Period is a significant era in Earth’s geological history, known for its vast coal deposits, lush tropical forests, and important evolutionary developments in both plant and animal life. This period occurred roughly 359 to 299 million years ago, following the Devonian Period and preceding the Permian Period.

Timeline and Subdivisions
The Carboniferous Period lasted approximately 60 million years and is often divided into two major sub-periods:
Mississippian (Early Carboniferous, 359 to 323 million years ago)
Pennsylvanian (Late Carboniferous, 323 to 299 million years ago)

In Europe, the name “Carboniferous” is commonly used for the entire period, while in North America, the terms Mississippian and Pennsylvanian are more commonly employed to distinguish the two phases.

Geological Characteristics
The Carboniferous is named after the extensive coal deposits found in rock strata from this period. These coal beds formed from the vast tropical forests and swampy environments that characterized much of the Earth during this time.

Supercontinents: During the Carboniferous, the supercontinent Pangaea began to form as smaller landmasses collided. For instance, Laurasia (which included North America and Eurasia) moved closer to Gondwana (which comprised present-day Africa, South America, Australia, and Antarctica), causing mountain-building events known as the Variscan (Europe) and Appalachian (North America) orogenies.

Coal Swamps: The period is famous for its coal-forming swamps, especially in lowland tropical regions near the equator. Organic material from trees, ferns, and other plants accumulated in waterlogged areas where it decomposed slowly, eventually forming the thick coal seams we find today.

Climate: The early Carboniferous climate was warm and tropical, with widespread, humid environments that favored the growth of extensive forests. However, as the period progressed, the climate became cooler and more arid, especially during the late Carboniferous.

Flora: A World of Giant Plants
One of the most distinctive features of the Carboniferous was its lush, forested landscape dominated by giant plants that thrived in the swampy environments. This period saw a huge increase in plant biomass, much of which eventually became coal.

Lycopods: Giant tree-like plants, such as Lepidodendron and Sigillaria, were common. These vascular plants could grow to heights of over 30 meters (100 feet) and had long, straight trunks with a distinct pattern of leaf scars.

Ferns and Seed Ferns: Ferns, both tree-sized and smaller varieties, thrived during the Carboniferous. Seed ferns (pteridosperms), which produced seeds rather than spores, also evolved and were abundant in the forests.

Sphenopsids: These plants, like Calamites, were jointed and hollow-stemmed, resembling modern-day horsetails. They grew in swampy environments and were important contributors to the ecosystem.

First Gymnosperms: Towards the end of the Carboniferous, the earliest gymnosperms (seed-producing plants like conifers) appeared. They were more adapted to the drier conditions that emerged during the later part of the period.

Fauna: Explosion of Insects and Amphibians
The Carboniferous saw major evolutionary developments in animal life, especially on land, where insects and amphibians flourished.

Insects: The Carboniferous is often called the “Age of Insects” due to the incredible diversity and size of the insects that evolved. Giant dragonfly-like insects, such as Meganeura, with wingspans of up to 70 cm (28 inches), dominated the skies. The warm, oxygen-rich atmosphere allowed some insects to grow to enormous sizes.

Amphibians: Amphibians became the dominant vertebrates during the Carboniferous, evolving from lobe-finned fish. They thrived in the swampy environments and grew to large sizes. Some, like Eryops, were predators in the freshwater habitats. Many early amphibians had sprawling limbs and relied heavily on water for breeding.

Tetrapod Evolution: The Carboniferous saw the continued evolution of tetrapods (four-limbed vertebrates) from fish. Reptiles made their first appearance late in the period. Unlike amphibians, reptiles had amniotic eggs, which allowed them to reproduce away from water, giving them an evolutionary advantage in drier environments.

Oxygen and Atmosphere
One of the unique features of the Carboniferous atmosphere was its high oxygen content. Oxygen levels during this period were significantly higher than today, likely around 35%, compared to the modern 21%. This high oxygen content contributed to:

The gigantic size of some insects and arthropods, which could grow larger because they relied on oxygen diffusion through their bodies.

An environment that could support vast, dense forests, which played a major role in sequestering carbon, reducing atmospheric CO2 levels, and contributing to global cooling toward the end of the period.

End of the Carboniferous: Climate Change and Extinction
Towards the end of the Carboniferous Period, significant climatic changes began to alter the Earth’s environment.

Glaciation: The cooling of the planet, particularly in the Southern Hemisphere, led to widespread glaciation during the Late Carboniferous. These glaciers formed in what is now South America, Africa, and Antarctica, which were then part of the supercontinent Gondwana.

Decline of Coal Swamps: As the climate became drier and cooler, the extensive coal swamps that had characterized much of the Carboniferous began to disappear. This had a major impact on the flora and fauna that had evolved to thrive in those environments.

Permian Extinction: Although the Carboniferous did not end with a mass extinction event, the changes in climate and habitat set the stage for significant evolutionary shifts in the Permian Period, which followed and culminated in the Permian-Triassic extinction event—the largest mass extinction in Earth’s history.

Significance of the Carboniferous
The Carboniferous Period left an indelible mark on Earth’s history, both geologically and biologically.

Coal Deposits: The extensive coal beds that formed during this period are some of the most important fossil fuel reserves today. These coal deposits have powered industrialization and continue to be a critical, though environmentally problematic, energy source.

Evolutionary Milestones: The Carboniferous saw significant evolutionary milestones, including the rise of the first reptiles, the diversification of amphibians, and the explosion of insect life. The development of amniotic eggs in reptiles was particularly important, as it allowed vertebrates to colonize a wider range of terrestrial environments.

Climate Impact: The period’s high oxygen levels and large-scale burial of organic material (in the form of coal) helped reduce atmospheric carbon dioxide, contributing to the long-term cooling that led to glaciation in the late Carboniferous.

Advertisement:

We get commissions for purchases made through links on this website. As an Amazon Associate we earn from qualifying purchases.