Each of the eras has characteristics that differentiate them from the others , hence they have been separated, although it is true that there were events that marked the end of each era.
An era is not the greatest measure of time there is. A supereon spans billions of years (more than 80% of Earth’s time) and then eons follow. An eon lasts about a billion years and the eras are the subdivisions of these.
So far there have been four eons: Phanerozoic , Proterozoic , Archaic, and Hadic . The last three are part of the Precambrian supereon . In each of these eons there were many geological eras that we will describe below.
Examples of geological eras
The following are all eras in the history of the planet.
- Cenozoic . It belongs to the Phanerozoic eon (it is its last era until now) and is divided by the Quaternary, Neogene and Paleogene periods. This era began 66 million years ago and continues to this day. This is said to be the era of slow cooling. It is characterized by being the beginning of a new era without dinosaurs, since the previous one was when they became extinct. For this reason, the number of animals increased, especially mammals.
- Mesozoic. It is part of the Phanerozoic eon and is divided by the Cretaceous, Jurassic and Triassic periods. It is known as the age of the dinosaurs and the cycad group of plants. It began 251 million years ago and ended 66 million years ago. It stands out for the beginning due to the displacement of the continents, and thanks to its good climate, a good setting was created for the emergence of thousands of animal species.
- Paleozoic. It is also part of the Phanerozoic and its periods are Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian. It began 541 million years ago and ended about 252 million years ago with the formation of the supercontinent Pangea.
- Neoproterozoic . It is a subdivision of the Proterozoic eon and the periods contained in it are Ediacaran, Cryogenic and Tonic. This era ended 542.0 ± 1.0 million years ago, but began 1 billion years ago. At this time there were many glacial formations. In its cryogenic period, the Earth probably froze completely, so in the Ediacaran period the first fossils of organisms appeared.
- Mesoproterozoic . Part of the Proterozoic eon and with periods called Aesthetic, Ectatic and Callimic . The era began 1.6 billion years ago and ended 1 billion years ago. There are some red algae that we still have, and many multicellular organisms such as filamentous actinobacteria.
- Paleoproterozoic. It is also part of the Proterozoic. His periods were: Stateric, Orosiric, Riácico and Sidérico. It began 2.5 billion years ago and ends 1.6 billion years ago. The continents were stabilized for the first time and the so-called Great Oxidation was generated due to photosynthesis made by cyanobacteria.
- Neoarchic . It is the last era of the Archaic eon and is not counted in periods. It lasted 300 million years, beginning 2.8 billion years ago and ending 2.5 billion years ago.
- Mesoarchic. This era is part of the Archaic eon and began 3.2 billion years ago to end 2.8 billion years ago (lasted 400 million years). Vaalbara, the first supercontinent, fragments at the end of this era.
- Paleoarchic. It begins 3.6 billion years ago and ends 3.2 billion years ago. It is another subdivision of Archaic.
- Eoarchic. It lasted 400 years, since it began 4 billion years ago and ended 3.6 billion years ago. It is the first era of the Archaic eon and begins after the Hadic eon.