Geologic Time Scale - I

The geologic time scale is a giant time scale representing the events in Earth's history over 4.6 billion years.

Scientists divide this timeline into big blocks of time called eons, further subdivided into eras, followed by periods, and then epochs.

The first three eons of the geological time scale, Hadean, Archean, and Proterozoic, are together called Precambrian, which began 4.6 billion years ago and lasted until about 541 million years ago.

The first simple life forms, like bacteria, appeared on Earth during this time. Later, they evolved into simple multicellular organisms and complex multicellular ones.

The next big eon, the Phanerozoic, is known as the "eon of visible life" and is divided into three main eras: Paleozoic, Mesozoic, and Cenozoic.

The Paleozoic era, which lasted from 541 to 252 million years ago, witnessed the rise of corals and saw the first fish, which are believed to have evolved into amphibians and reptiles in later stages.

However, this era ended with a massive extinction that wiped out most species.