The geological time scale divides up the history of the earth based on life-forms that have existed during specific times since the creation of the planet. These divisions are called geochronologic units (geo: rock, chronology: time).
Most of these life-forms are found as fossils, which are the remains or traces of an organism from the geologic past that has been preserved in sediment or rock. Without fossils, scientists may not have concluded that the earth has a history that long precedes mankind (South Carolina university).
The Geological Time Scale is divided by the following divisions:
- Eons: Longest subdivision; based on the abundance of certain fossils
- Eras: Next to longest subdivision; marked by major changes in the fossil record
- Periods: Based on types of life existing at the time
- Epochs: Shortest subdivision; marked by differences in life forms and can vary from continent to continent.
From primordial oceans to towering mountains and the rise and fall of species, the geological time scale is a record of constant transformation. What pivotal moments does it highlight in Earth’s incredible journey?
