Eras & Periods

Time is divided into big chunks called periods and massive chunks called eras.

The last three eras are:

  • Paleozoic Era (541 to 252 million years ago) – The Dawn of Life on Land
  • Mesozoic Era (252 to 66 million years ago) – The Age of Dinosaurs
  • Cenozoic Era (66 million years ago to now) – The Age of Mammals

The Paleozoic Era: The Dawn of Life on Land

The Paleozoic Era is a fascinating chapter in Earth’s history, way before the dinosaurs appeared. This era, lasting from about 541 to 252 million years ago, saw the development of many early life forms and dramatic changes to our planet.

The Paleozoic Era is divided into six main periods:

  1. Cambrian Period (541 to 485 million years ago)
    • Explosion of Life: The Cambrian is famous for the “Cambrian Explosion,” a time when many new types of animals appeared. Oceans were filled with strange creatures like trilobites, which looked like underwater bugs, and the first ancestors of modern animals.
    • First Eyes: Many animals developed the first complex eyes, helping them see better and find food.
  2. Ordovician Period (485 to 444 million years ago)
    • Sea Life Flourishes: Life continued to thrive in the oceans. Early fish without jaws and coral reefs began to form.
    • First Land Plants: Simple plants started to grow on land, setting the stage for future life on dry land.
  3. Silurian Period (444 to 419 million years ago)
    • Jawed Fish: Fish with jaws appeared, becoming the top predators in the seas.
    • Land Plants and Animals: More complex plants and the first tiny land animals, like early spiders and centipedes, started to spread.
  4. Devonian Period (419 to 359 million years ago)
    • Age of Fish: Fish became very diverse and abundant. The first amphibians, animals that could live both in water and on land, started to evolve.
    • Forests Begin: The first real forests with tall trees and ferns appeared.
  5. Carboniferous Period (359 to 299 million years ago)
    • Swampy Forests: Large swampy forests covered much of the land, with giant ferns and huge insects.
    • Early Reptiles: The first reptiles, ancestors of the dinosaurs, appeared.
  6. Permian Period (299 to 252 million years ago)
    • Big Changes: The climate became drier, and many new types of reptiles evolved.
    • Mass Extinction: The Permian Period ended with the largest mass extinction in Earth’s history, wiping out many species and paving the way for the rise of dinosaurs in the next era.

The Mesozoic Era: The Age of Dinosaurs

The era when dinosaurs roamed the Earth is called the Mesozoic Era, and it lasted about 180 million years.

The Mesozoic Era is divided into three periods:

  1. Triassic Period (252 to 200 million years ago)
    • First Dinosaurs: This is when the very first dinosaurs appeared. They were usually small and walked on two legs. Plateosaurus, a long-necked dinosaur, lived during this time.
    • Early Reptiles: Before dinosaurs became the rulers of the land, early reptiles and amphibians were more common.
  2. Jurassic Period (200 to 145 million years ago)
    • Dinosaur Boom: Dinosaurs became the kings and queens of the Earth. Giant plant-eaters like Brachiosaurus and fierce hunters like Allosaurus ruled the land.
    • First Birds: During the Jurassic, some dinosaurs started to evolve into the first birds.
  3. Cretaceous Period (145 to 66 million years ago)
    • Dinosaur Diversity: Dinosaurs were very different from one another during this time. You could find massive ones like Tyrannosaurus rex and spiky ones like Triceratops.
    • Flowering Plants: The first flowers bloomed, and new kinds of plants spread across the land.
    • End of the Dinosaurs: This period ended with a huge asteroid impact, causing many dinosaurs to go extinct.

The Cenozoic Era: The Age of Mammals

After the dinosaurs disappeared, a new era began called the Cenozoic Era. This is the era we’re still in today!

The Cenozoic Era started about 66 million years ago and is divided into three main periods:

  1. Paleogene Period (66 to 23 million years ago)
    • Rise of Mammals: After the dinosaurs went extinct, mammals started to take over. Some were small, but others grew very big. Early ancestors of horses, whales, and primates appeared.
    • First Grasses: Grasses began to spread, changing the landscape and providing food for many new types of animals.
    • Bird Evolution: Birds became very diverse, filling many roles that were once held by flying dinosaurs.
  2. Neogene Period (23 to 2.6 million years ago)
    • Mammals Everywhere: Many modern groups of mammals began to appear, such as elephants, cats, and rhinos.
    • Grasslands Spread: Grasslands and savannas expanded, leading to the development of large grazing animals.
    • Ancient Humans: The earliest ancestors of humans started to evolve during this time.
  3. Quaternary Period (2.6 million years ago to present)
    • Ice Ages: There were several Ice Ages, where large parts of the Earth were covered in ice. Mammoths and saber-toothed cats lived during these cold times.
    • Rise of Humans: Modern humans appeared and began to spread across the world. They developed tools, art, and started farming.
    • Present Day: We live in the Holocene Epoch, which is the latest part of the Quaternary Period.
Scroll to Top