Final answer:
The terms Tertiary (now replaced by Paleogene and Neogene) and Quaternary refer to geological time units that are part of the geological time scale, categorizing Earth's history.
Step-by-step explanation:
The terms Tertiary (which was replaced by Paleogene and Neogene in 2003) and Quaternary are best described as geological time units. These terms are part of the geological time scale that categorizes the history of Earth into different units of time, such as eons, eras, periods, epochs, and ages. The Quaternary is the current period and follows the Neogene Period.Geologic periods represent significant spans of time during which specific rocks were formed, characteristic fossils can be found, and major geologic events occurred. The Tertiary was split into the Paleogene and Neogene periods to provide more precise geological categorization. These units help geologists and paleontologists understand Earth's history and the evolution of life through time.It's also important to note that geologists use various abbreviations and symbols for these periods on geologic maps, and while some older terms might still see use, it's crucial to be aware of the updated nomenclature.