Timeline of Earth
Introduction
The history of Earth spans billions of years, marked by significant geological, biological, and climatic changes. This timeline provides an overview of the major events that have shaped our planet.
Geological Timeline
Eon, Era, Period, and Epoch Breakdown
- Eons: The largest divisions of geological time, encompassing billions of years.
- Eras: Subdivisions of eons, lasting hundreds of millions of years.
- Periods: Divisions of eras, characterized by notable geological and biological events.
- Epochs: Smaller units within periods, marking distinct changes in Earth's history.
Timeline of Earth's History
Precambrian (4.6 billion - 541 million years ago)
| Time | Event |
|---|---|
| 4.6 billion years ago | Earth forms from a protoplanetary disk. |
| 4.5 billion years ago | The Moon forms after a giant impact with Earth. |
| 4 billion years ago | Oldest known rocks form, indicating a solid crust. |
| 3.5 billion years ago | First evidence of life: microbial fossils. |
| 2.5 billion years ago | Beginning of the Great Oxidation Event. |
| 1.8 billion years ago | Emergence of eukaryotic cells. |
| 1 billion years ago | Multicellular organisms begin to appear. |
Phanerozoic Eon (541 million years ago - Present)
Paleozoic Era (541 - 252 million years ago)
Cambrian Period (541 - 485 million years ago)
- Cambrian Explosion: Rapid diversification of life forms; most major animal phyla appear.
Ordovician Period (485 - 444 million years ago)
- First vertebrates and extensive marine life; plants colonize land.
Silurian Period (444 - 419 million years ago)
- Development of vascular plants; first arthropods on land.
Devonian Period (419 - 359 million years ago)
- Age of Fishes; first tetrapods and forests emerge.
Carboniferous Period (359 - 299 million years ago)
- Extensive coal forests; amphibians dominate; first reptiles.
Permian Period (299 - 252 million years ago)
- Pangaea supercontinent forms; ends with the Permian-Triassic Extinction.
Mesozoic Era (252 - 66 million years ago)
Triassic Period (252 - 201 million years ago)
- First dinosaurs and mammals; conifers dominate landscapes.
Jurassic Period (201 - 145 million years ago)
- Dinosaurs thrive; first birds; flowering plants begin to evolve.
Cretaceous Period (145 - 66 million years ago)
- Flowering plants diversify; ends with the Cretaceous-Paleogene Extinction.
Cenozoic Era (66 million years ago - Present)
Paleogene Period (66 - 23 million years ago)
- Mammals and birds radiate and diversify; Earth's climate cools.
Neogene Period (23 - 2.6 million years ago)
- Continents take modern shapes; early hominins appear.
Quaternary Period (2.6 million years ago - Present)
Pleistocene Epoch (2.6 million - 11,700 years ago)
- Repeated glacial cycles; rise of modern humans.
Holocene Epoch (11,700 years ago - Present)
- Human civilization develops; agriculture, cities, and technological advances.
"Anthropocene" (Proposed)
- Marked by significant human impact on Earth's geology and ecosystems.
Human Impact
Title: Human Impact
Description:
The Anthropocene epoch is proposed to highlight the profound and lasting impact humans have had on the planet's climate, ecosystems, and biodiversity.
Key Concepts
- Great Oxidation Event: A time when oxygen levels in Earth's atmosphere dramatically increased due to photosynthetic organisms.
- Cambrian Explosion: A period of rapid evolutionary development where many major animal groups first appeared.
- Permian-Triassic Extinction: The largest mass extinction in Earth's history, wiping out approximately 90% of marine species and 70% of terrestrial vertebrates.
- Cretaceous-Paleogene Extinction: A mass extinction event likely caused by an asteroid impact, leading to the demise of the dinosaurs.
- Anthropocene: A proposed geological epoch emphasizing the significant human impact on Earth's environment and geology.
Conclusion
Earth's history is a complex tapestry of geological transformations, biological evolutions, and climatic shifts. From the formation of the planet to the rise of human civilization, each era and period has contributed to the world we know today.