Key Geological Time Periods to Know

Geological time periods outline Earth's history, showcasing the evolution of life and major geological events. From the Precambrian's simple organisms to the Cenozoic's diverse mammals, understanding these eras helps us grasp our planet's dynamic past and its impact on today’s ecosystems.

1. Precambrian

   • Covers approximately 88% of Earth's history, from the formation of the Earth (about 4.6 billion years ago) to around 541 million years ago.
   • Includes the formation of the first simple life forms, primarily single-celled organisms like bacteria and archaea.
   • Major geological developments include the formation of the Earth's crust and the atmosphere, as well as the emergence of photosynthesis.

2. Paleozoic Era

   • Spans from about 541 to 252 million years ago and is characterized by the emergence of diverse marine life and the colonization of land.
   • Divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
   • Notable for the development of fish, amphibians, and the first reptiles, as well as significant plant evolution.

3. Mesozoic Era

   • Lasted from about 252 to 66 million years ago, often referred to as the "Age of Reptiles" due to the dominance of dinosaurs.
   • Divided into three periods: Triassic, Jurassic, and Cretaceous.
   • Marked by the rise of mammals and birds, as well as the breakup of the supercontinent Pangaea.

4. Cenozoic Era

   • Began around 66 million years ago and continues to the present, known as the "Age of Mammals."
   • Divided into three periods: Paleogene, Neogene, and Quaternary.
   • Characterized by the diversification of mammals and birds, as well as significant climatic changes leading to the current ice ages.

5. Cambrian Period

   • Lasted from about 541 to 485 million years ago, known for the "Cambrian Explosion," a rapid diversification of life.
   • First appearance of many major groups of animals, including trilobites and early arthropods.
   • Significant increase in the complexity of marine ecosystems.

6. Ordovician Period

   • Spanned from about 485 to 444 million years ago, marked by a great diversification of marine life.
   • First evidence of land plants and the appearance of the first coral reefs.
   • Ended with a major mass extinction event, likely due to a short ice age.

7. Silurian Period

   • Lasted from about 444 to 419 million years ago, characterized by the stabilization of the Earth's climate and sea levels.
   • Significant developments in fish, including the first jawed fish.
   • Emergence of the first terrestrial plants and arthropods.

8. Devonian Period

   • Spanned from about 419 to 359 million years ago, often called the "Age of Fishes" due to the diversity of fish species.
   • First appearance of amphibians and significant advancements in plant life, including the first trees.
   • Ended with a series of extinction events that affected marine life.

9. Carboniferous Period

   • Lasted from about 359 to 299 million years ago, known for extensive forests and the formation of coal deposits.
   • Significant evolution of amphibians and the first reptiles appeared.
   • High levels of oxygen in the atmosphere supported large insects and other arthropods.

10. Permian Period

    • Spanned from about 299 to 252 million years ago, marked by the formation of the supercontinent Pangaea.
    • Dominance of reptiles and the first true mammals appeared.
    • Ended with the largest mass extinction in Earth's history, known as the Permian-Triassic extinction event.

11. Triassic Period

    • Lasted from about 252 to 201 million years ago, characterized by the recovery of life after the Permian extinction.
    • First dinosaurs and mammals appeared, along with the first true turtles.
    • Ended with a significant extinction event that paved the way for the dominance of dinosaurs.

12. Jurassic Period

    • Spanned from about 201 to 145 million years ago, known for the dominance of dinosaurs and the first birds.
    • Significant diversification of plant life, including the rise of flowering plants.
    • Major geological changes, including the further breakup of Pangaea.

13. Cretaceous Period

    • Lasted from about 145 to 66 million years ago, marked by the peak of dinosaur diversity and the first appearance of flowering plants.
    • Ended with a mass extinction event, likely caused by an asteroid impact, leading to the extinction of most dinosaurs.
    • Significant changes in marine life, including the rise of modern groups of fish.

14. Paleogene Period

    • Spanned from about 66 to 23 million years ago, characterized by the rapid evolution of mammals and birds after the dinosaur extinction.
    • Development of modern mammal groups and the first primates appeared.
    • Significant climatic changes, leading to the establishment of modern ecosystems.

15. Neogene Period

    • Lasted from about 23 to 2.6 million years ago, marked by the further evolution of mammals and birds.
    • Development of grasslands and the rise of large herbivores and predators.
    • Significant geological changes, including the uplift of mountain ranges and changes in ocean currents.

16. Quaternary Period

    • Began around 2.6 million years ago and continues to the present, characterized by repeated glacial and interglacial cycles.
    • Emergence and evolution of Homo sapiens and significant cultural developments.
    • Ongoing changes in climate and ecosystems, with a focus on human impact on the environment.