Final answer:
The 5 basic time units that make up the geologic time scale are eons, eras, periods, epochs, and ages.
Step-by-step explanation:
The 5 basic time units that make up the geologic time scale are eons, eras, periods, epochs, and ages.
These units are used to organize Earth's history and the evolution of life based on significant events such as tectonic, biological, and climatic changes.
The time scale is continuously revised as new research provides more accurate dating of rocks, minerals, and fossils.