Final answer:
The geologic timescale is organized by major climate changes, natural disasters, and the evolution of life, particularly fossil groups, not by equal time intervals or the date of fossil discovery. It includes eons, eras, periods, epochs, and ages and employs radiometric dating to assign ages to these divisions.
Step-by-step explanation:
The geologic timescale is organized primarily based on significant changes in Earth's geology, climate, and the evolution of life rather than intervals of time of equal length. It is divided into eons, eras, periods, epochs, and ages. These divisions reflect major events such as mass extinctions, the appearance and disappearance of flora and fauna, and significant climatic shifts that have shaped the planet over its extensive history.
- by major changes in ancient Earth's climate or major natural disasters
- by the appearance, disappearance, or change in dominance (frequency) of particular fossil groups
Fossils play a critical role in organizing the timescale, but it's not organized by the date they were discovered. The process of radiometric dating has allowed geologists to assign numerical ages to these divisions, which helps in understanding the timeline of significant events relative to one another. Earth's long-spanning history, especially during the Precambrian time, means that geologists know more about the more recent past than the distant geological past.