Introduction
The timeline of Earth spans billions of years, marked by significant geological, biological, and climatic events. This guide highlights key moments in Earth's history, from its formation to major evolutionary milestones.
Timeline of Major Events
Hadean Eon (4.6 - 4 billion years ago)
- 4.6 billion years ago: Earth forms from the solar nebula.
- 4.5 billion years ago: The Moon is created, possibly from a giant impact.
Archean Eon (4 - 2.5 billion years ago)
- 3.8 billion years ago: First signs of life appear; simple microbial life forms.
- 3.5 billion years ago: Oldest known fossils of cyanobacteria.
Proterozoic Eon (2.5 billion - 541 million years ago)
- 2.4 billion years ago: The Great Oxidation Event introduces oxygen to the atmosphere.
- 1.2 billion years ago: Multicellular organisms begin to emerge.
- 750-600 million years ago: Snowball Earth glaciations occur.
Phanerozoic Eon (541 million years ago - Present)
Paleozoic Era (541 - 252 million years ago)
- 541 million years ago: Cambrian Explosion; rapid diversification of life.
- 485 million years ago: Ordovician Period; first vertebrates and land plants appear.
- 444 million years ago: Silurian Period; early land animals and vascular plants evolve.
- 419 million years ago: Devonian Period; "Age of Fishes" and first amphibians.
- 359 million years ago: Carboniferous Period; extensive forests and giant insects.
- 299 million years ago: Permian Period; formation of the supercontinent Pangaea.
Mesozoic Era (252 - 66 million years ago)
- 252 million years ago: Permian-Triassic extinction event, the largest in Earth's history.
- 247 million years ago: Triassic Period; early dinosaurs and mammals evolve.
- 201 million years ago: Jurassic Period; dinosaurs dominate, first birds appear.
- 145 million years ago: Cretaceous Period; flowering plants emerge, T. rex roams.
- 66 million years ago: Cretaceous-Paleogene extinction; dinosaurs go extinct.
Cenozoic Era (66 million years ago - Present)
- 66 million years ago: Paleogene Period; mammals diversify and dominate.
- 23 million years ago: Neogene Period; early hominins and modern animals evolve.
- 2.6 million years ago: Quaternary Period; ice ages and the rise of Homo sapiens.
Pangaea: The Supercontinent
Formation and Impact
- 299-200 million years ago: During the late Paleozoic and early Mesozoic eras, Earth's landmasses combined to form the supercontinent Pangaea.
- Climate Change: Pangaea's massive size created extreme climatic conditions, with arid deserts in the interior and humid regions along the coasts.
- Ocean Circulation: The configuration of continents altered ocean currents, influencing global climate patterns.
- Biological Evolution: The connected landmass facilitated the spread of terrestrial animals and plants, leading to significant evolutionary developments.
Geological Significance
- Plate Tectonics: Pangaea's formation and subsequent breakup demonstrated the dynamic nature of Earth's crust, driven by plate tectonics.
- Continental Drift: The breakup of Pangaea into smaller continents shaped the modern geographic distribution of continents and oceans.
Key Phases in Pangaea’s Evolution
Formation
- Late Carboniferous to Early Permian: Pangaea reaches its maximum extent, uniting almost all of Earth's landmasses into a single supercontinent.
Breakup
- 200 million years ago: Pangaea begins to rift apart during the Triassic Period, leading to the formation of the Atlantic Ocean and the separation of continents.
Visual Representation
Image Source: Wikimedia Commons
Summary
Pangaea was a monumental geological formation that reshaped Earth's climate, geography, and biological evolution. Its legacy is seen in the distribution of continents, the evolution of species, and the understanding of plate tectonics.