Geology is the study of Earth's history and the way it is shaped by different processes happening over time. A timeline of geology is like a map of Earth's history that shows how it has changed over millions of years. It tells us what ancient rocks and fossils used to look like and how large continents used to be. We can also see how different features, like mountains and valleys, were formed and what type of life was on Earth at different points in its history. It helps us to understand why some places are dry now and others are wet; why some rocks are very old while others are relatively new. Geology helps us to understand how Earth changes and how humans can help protect the environment.