Geological era

Have you ever looked at really big rocks or mountains and wondered how they got there? Well, a long, long time ago there were different time periods on Earth where things were very different than they are now. These time periods are called geological eras.

Think of it like a very long storybook about Earth's history. Each chapter in the book is a different era, and in each chapter things were different than they are now. For example, in one chapter called the "Mesozoic era," there were giant reptiles called dinosaurs that roamed around. But in the chapter we live in now, called the "Cenozoic era," there are no more dinosaurs and mammals like us have taken their place.

Each geological era can last millions of years, which is longer than you can imagine. Scientists study the rocks and fossils from each era to figure out what the Earth was like during that time. So next time you see a big mountain, you can imagine it's from a different chapter in Earth's history!