Final answer:
The geological time scale is divided into eons, eras, periods, and epochs, each representing different spans of time and significant geological and biological events. The current eon is the Phanerozoic eon, which is divided into three eras. The smallest unit of time is the epoch.
Step-by-step explanation:
Geological Time Scale
The geological time scale is a timeline that scientists use to divide Earth's history into different time intervals based on major geological and biological events. It is divided into four basic time units: eons, eras, periods, and epochs.
Eons:
An eon is the longest unit of time in the geological time scale, lasting billions of years. The current eon is the Phanerozoic eon, which began around 541 million years ago and continues to the present day.
Eras:
An era is a subdivision of an eon and typically lasts tens to hundreds of millions of years. The Phanerozoic eon is divided into three eras: the Paleozoic era, the Mesozoic era, and the Cenozoic era. Each era is characterized by major geological and biological events, such as the appearance of complex life forms during the Paleozoic era.
Periods:
A period is a subdivision of an era and typically lasts several tens of millions of years. The Mesozoic era, for example, is divided into three periods: the Triassic period, the Jurassic period, and the Cretaceous period. Each period is marked by distinct geological and biological changes, such as the extinction of dinosaurs at the end of the Cretaceous period.
Epochs:
An epoch is the smallest unit of time in the geological time scale, lasting several million years. The Cenozoic era is divided into several epochs, such as the Paleocene epoch, the Eocene epoch, and the Holocene epoch. Each epoch is characterized by specific climate, geological, and biological conditions.
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