Eons: The largest unit of geological time, representing hundreds of millions to billions of years. There are four eons:
* Hadean Eon: The earliest eon, characterized by a very hot Earth and the formation of the first oceans and continents.
* Archean Eon: Marked by the emergence of the first life forms.
* Proterozoic Eon: Characterized by the development of single-celled organisms and the first multicellular life.
* Phanerozoic Eon: The most recent eon, spanning the last 541 million years and characterized by the diversification of complex life forms.
Eras: Within each eon, there are several eras, representing tens to hundreds of millions of years. Here are the eras of the Phanerozoic Eon:
* Paleozoic Era: "Ancient life", characterized by the rise of marine invertebrates, fishes, amphibians, and the first reptiles.
* Mesozoic Era: "Middle life", dominated by dinosaurs, reptiles, and the emergence of flowering plants.
* Cenozoic Era: "Recent life", characterized by the diversification of mammals and birds, the development of modern continents, and the appearance of humans.
Periods: Each era is divided into several periods, spanning tens of millions of years. These are some examples:
* Paleozoic: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian
* Mesozoic: Triassic, Jurassic, Cretaceous
* Cenozoic: Paleogene, Neogene, Quaternary
Epochs: Periods are further divided into epochs, which cover a few million years. Examples:
* Paleogene: Paleocene, Eocene, Oligocene
* Neogene: Miocene, Pliocene
* Quaternary: Pleistocene, Holocene
Ages: The smallest unit of geological time, ages represent hundreds of thousands to millions of years. They are mainly used within epochs to further define specific periods.
It's important to note that the boundaries between these units are not always precise and may vary depending on the source. The geological timescale is constantly being refined as scientists discover new evidence.
