Geological time scale
Geological Time Scale (GTS)
A chart that shows Earth’s history from its beginning till now.
2. Eon
The biggest time unit.Example: Hadean, Archean, Proterozoic, Phanerozoic
3. Era
Large divisions inside an eon.Example: Paleozoic, Mesozoic, Cenozoic
4. Period
Smaller divisions inside an era.Example: Jurassic, Triassic, Cretaceous
5. Epoch
Smaller divisions inside a period.Example: Holocene, Pleistocene
6. Age
The smallest time unit.
7. Fossils
Remains or signs of ancient life used to study past time periods.
8. Extinction
When a species completely disappears.
9. Evolution
Change in living things over time.
10. Mass Extinction
A time when many species die out suddenly.
11. Ice Age
A long period when Earth had very cold temperatures and large ice sheets.
12. Dinosaurs
Reptiles that lived mainly in the Mesozoic Era.
13. Precambrian
Early Earth time before complex life appeared.
14. Quaternary Period
The period we are living in now.
15. Holocene Epoch
The epoch we are living in now.
Interesting points:
Earth is very old
The Earth is about 4.5 billion years old—much older than any living thing today!
2. Humans are very new
If Earth’s history were a 24-hour day, humans appear only in the last few seconds.
3. Most life was simple at first
For billions of years, only tiny organisms lived on Earth— no plants, no animals.
4. Dinosaurs ruled for a long time
Dinosaurs lived for more than 160 million years, much longer than humans have!
5. Four big mass extinctions happened
These events wiped out many species at once and changed Earth’s life completely.
6. One asteroid changed everything
An asteroid hit Earth 66 million years ago and caused the extinction of the dinosaurs.
7. Continents keep moving
Land on Earth was once joined in a supercontinent called Pangaea.
8. New species keep evolving
Every time Earth changes—climate, land, or oceans—new species appear.
9. Ice ages come and go
Earth has had many ice ages, not just one.
10. We live in the Holocene
This is the warm period after the last ice age—perfect for humans.
Main points:
Earth is extremely old
The Earth is about 4.5 billion years old.
2. Geological Time Scale shows Earth’s history
GTS is like a timeline that tells how life and Earth changed over time.
3. Time is divided into parts
The main divisions are:
Eon
Era
Period
Epoch
Age
4. Life changed slowly
Early life was simple; later it became more complex like plants, fish, dinosaurs, and humans.
5. Mass extinctions changed Earth
Several big extinction events wiped out many species and allowed new species to evolve.
6. Dinosaurs lived in the Mesozoic Era
This era is known as the Age of Reptiles.
7. Humans appeared very late
Humans came only in the Cenozoic Era, very close to today.
8. Continents moved over time
Due to plate movement, continents were once joined together as Pangaea.
9. Fossils help us understand the past
Scientists use fossils to learn what life was like long ago.
10. We live in the Holocene Epoch
This is the latest part of the Quaternary Period.
Definition:
The Geological Time Scale is a timeline that shows the history of the Earth from its beginning to now, divided into different time periods based on important changes in life and the planet.
Fun Fact:
If Earth’s history were a 24-hour clock, humans would appear in the last few seconds!”