The Evolution of Earth: The Cycle of Extinction Explained
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The Natural Cycle of Extinction
Extinction has always been an intrinsic part of Earth's natural history. However, certain extinction events have had more profound effects than others. Welcome to Part 45 of our exploration into Earth's history.
Easter Egg, © the Author
The current analysis focuses on a significant period spanning from 300 to 200 million years ago, beginning with the Permian Period (299 to 252 million years ago).
Understanding Earth's Climate States
Earth's climate can be categorized into two primary states: icehouse and greenhouse. An icehouse state is characterized by the presence of polar ice caps, while a greenhouse state occurs in their absence. Presently, we are situated within an icehouse phase, similar to the conditions of the Permian period. Notably, 50 million years prior, during the Famennian Glaciation, polar ice caps had emerged and persisted.
During this time, the atmosphere experienced its lowest recorded levels of carbon dioxide. But where did this carbon go? It was safely stored in coal, as discussed in Part 44.
Formation of Pangaea and the Age of Reproduction
As the supercontinent Pangaea formed, it extended from the northern to the southern poles. This continental shift led to the emergence of new mountain ranges, altering the climate and giving rise to deserts. The drier conditions were unsuitable for amphibians, which relied on water for reproduction, but they were ideal for amniotes—creatures that laid shelled eggs, such as reptiles. This era became known as the Age of the Egg.
Dimetrodon: A Prehistoric Marvel
My favorite prehistoric creature thrived during this time: the Dimetrodon. This remarkable reptile, technically classified as a pelycosaur, measured between 2 to 4 meters in length and was distinguished by a prominent sail on its back. Such a stunning creature deserves a Google search to appreciate its beauty.
Overall, this period was relatively uneventful in Earth’s history—until chaos erupted.
The Catastrophe of Extinction
In northern Pangaea, a catastrophic series of events unfolded. Over thousands of years, an astounding 4 million cubic kilometers of lava erupted from what is now known as the Siberian Traps. This volume could fill the Mediterranean Sea or cover the entirety of Australia.
This volcanic activity released a deluge of greenhouse gases, leading to severe air pollution, ocean acidification, and the annihilation of marine life on an unprecedented scale. Meanwhile, bacteria thrived, producing hydrogen sulfide that further contaminated the environment. Ultimately, 95% of all species—including my beloved Dimetrodon—perished. This marked the most devastating of the five major extinction events.
Reflecting on Current Trends
As of 2024, our carbon dioxide emissions outpace those recorded during the late Permian. Just a thought to consider.
The Rise of the Triassic Period
Following the extensive carbon emissions, the planet transitioned from an icehouse to a greenhouse state, ushering in the Triassic Period (252 to 201 million years ago). During this time, the first true mammals emerged, albeit as small, inconspicuous nocturnal creatures. For now, we can overlook their significance.
This era was predominantly characterized as the Age of Reptiles. Archosaurs, protorosaurs, and aetosaurs—all descendants of a select few reptilian survivors from the Permian extinction—flourished. However, volcanic activity resumed, likely triggered by the initial breakup of Pangaea, leading to yet another major extinction event.
The End of the Triassic
The Triassic period concluded much like it began—amidst death and devastation. But who would emerge as the survivors this time? The answer is well-known: it was the dinosaurs.
This article represents Part 45 in a series of 50, chronicling 100-million-year intervals in Earth's history. For further reading, refer to Part 44: FISH AND COAL and Part 46: DINOSAUR. If you wish to explore all articles, please follow my work.