Geological Time Scale Eras to Know for Earth Science

The Geological Time Scale breaks down Earth's 4.6 billion-year history into eras, highlighting major events in life and geology. From the Precambrian's simple life forms to the Cenozoic's mammals, each era reveals the planet's dynamic evolution.

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.
   • Characterized by the formation of the Earth's crust, oceans, and atmosphere, as well as the emergence of simple life forms, primarily single-celled organisms.
   • Major events include the appearance of prokaryotic life, the development of photosynthesis, and the rise of eukaryotic cells.
   • The end of the Precambrian is marked by the Ediacaran Period, which saw the first multicellular organisms.

2. Paleozoic

   • Spans from about 541 million years ago to 252 million years ago, marked by significant diversification of life.
   • Divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian, each showcasing different evolutionary advancements.
   • Notable for the Cambrian Explosion, a rapid increase in the diversity of life forms, including the first appearance of many major animal groups.
   • The Paleozoic era ended with the Permian-Triassic extinction event, the largest mass extinction in Earth's history, which wiped out approximately 90% of species.

3. Mesozoic

   • Lasts from about 252 million years ago 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, each marked by significant geological and biological changes.
   • The era saw the emergence of mammals and birds, as well as the development of flowering plants.
   • Ended with the Cretaceous-Paleogene extinction event, which led to the extinction of the dinosaurs and many other species.

4. Cenozoic

   • Begins around 66 million years ago and continues to the present, known as the "Age of Mammals" due to the rise of mammals and birds after the dinosaurs' extinction.
   • Divided into three periods: Paleogene, Neogene, and Quaternary, with significant climatic changes and the evolution of modern flora and fauna.
   • Characterized by the development of grasslands, the rise of primates, and the eventual emergence of humans in the Quaternary period.
   • The Cenozoic is marked by ongoing geological activity, including the formation of mountain ranges and changes in sea levels.