The Geologic Timescale

Geologic Timescale

The geologic time scale is a system of chronologic measurements that relate stratigraphy to time that is used to describe the timing and relationships between events that have occurred during the history of the Earth. These "events" are broken up into Eons, Eras, and Periods. Each of these has a different name because the world was and still is constantly changing. The environment, including the organisms living there, was changing.

The Precambrian is the first Era of the geologic timescale. During this era, the earth, along with the first one celled and multi-celled organisms, was created. The second era is known as the Paleozoic Era. It's periods include the Cambrian, the Ordovician, the Silurian, the Devonian, the Carboniferous: Mississippian, the Carboniferous: Pennsylvanian, and the Permian periods. During this era, the first organisms with shells, fishes, large amphibians, and reptiles were found. Also, the first insects were fossilized in this era and at the end of it many marine organisms became extinct. The Mesozoic Era follows the Paleozoic Era. It includes the Triassic, Jurassic, and Cretaceous periods. In this era, Dinosaurs became dominant and the first birds and flowering plants developed. The next era is the Cenozoic Era. It consists of the Tertiary and the Quaternary periods. These periods are the "Age of Mammals" because it is when the first humans and other mammals developed. Also, this time period is when the dinosaurs became extinct.

The Geologic Timescale is used by many scientists to find relationships in the earth's history. It is based on using sedimentary rock and by finding evidence of life in the different layers. In conclusion, these different "events" might have happened due to meteor strikes, and other natural disasters.