1. Geologic Time

2. Our Planet’s History
Geologic time is the time frame of our planet’s history.
While 30,000 year old cave paintings seem really old to us when compared to modern art, this is a miniscule amount of time in comparison to the age of our planet.
Earth has been in existence for 4,600,000,000 years billion years!

3. How do Scientists Know the Earth’s Age?
When scientists discovered radioactivity, they were able to develop radiometric dating methods to determine the age of ancient rocks.
The consistency of the results gives scientists confidence that the ages are correct to within a few percent.
Ancient rocks exceeding 3.5 billion years in age have been found on all of Earth's continents.

4. When did humans first appear?
4,600,000,000 years includes…
The birth of our planet
Evolution of the first single-celled life-forms
Assembly of at least three supercontinents (Rodinia, Pannotia, and Pangaea)
The rise and fall of dinosaurs
The colonization and dominance of flowering plants
When did humans first appear?

5. Modern Cro-Magnon humans showed up less than 50,000 years ago.
Understanding the true meaning and scale of Geologic Time can be challenging, so today we are going to do two activities to help you put Geologic Time in perspective.

6. Activity #1: Clapping the Earth’s Life
Let’s represent one decade (10 years) in seconds.
Each year will be represented by one second which equals one clap of the hands clap = 1 second = 1 year
How long does it take to clap your age?
If your grandmother is 70, how long will it take to clap her age?

7. How long would it take to clap the age of this
100-year-old tortoise in…
seconds? __________
minutes? __________________
(Remember: there are 60 seconds per minute)
100 sec and 1 min 40 sec

8. How long would it take in minutes…
To clap the age of the 234-year-old Declaration of Independence?
234 seconds  60 sec/min = __________min
To clap the age of the Great Pyramid of Egypt built 4571 years ago?
4571 seconds  60 sec/min = _________ min
3.9 min and min

9. How long would it take to clap the Earth’s Age, 4.6 billion years?
Do you think you could clap the Earth’s Age in your own lifetime? Circle one.
YES NO

10. The Calculation… There are 60 seconds per minute
60 sec/min X 60 min/hr = 3,600 sec/hr
3,600 sec/hr X 24 hrs/day = 86,400 sec/day
86,400 sec/day X days/year = 31,557,600 sec/year
How long will it take to clap 4,600,000,000 seconds?
4,600,000,000 seconds  31,600,000

11. 4,600,000,000 seconds  31,600,000 seconds/year =
That’s almost years!
Remember, your own lifetime can be clapped in less than 15 seconds!

12. Activity #2: TP Timeline
Now we are going to make a TP Timeline!
The tissue we’re using contains 176 sheets per roll.
The entire roll represents the earth’s lifetime, so we need to figure out how many years each square sheet of tissue will represent.
4,600,000,000  176 sheets = 26 million years/sheet

13. Major Earth Events
We are going to label the tissue timeline to mark significant events in the Earth’s history.
We’ll start from today and work backward in time.

14. TP Timeline
Early modern humans – 130,000 years ago. That’s 0.5% of one sheet from today (the edge of the first sheet)
The first hominids – 7,000,000 years ago 27% of one sheet from today
Many dinosaurs go extinct – 65,000,000 years ago sheets from today
First bird fossils formed – 174,000,000 years ago sheets from today
“The Great Dying” – 245,000,000 years ago 9.4 sheets from today
First fish, first insects – 490,000,000 years ago 18.8 sheets from today

15. Abundant shell life = 542,000,000 years ago 21 sheets from today
Oxygen occurs in Earth’s atmosphere – 2,000,000,000 years ago sheets from today
First life forms (prokaryotes) – 3,600,000,000 years ago sheets from today
Oldest rocks on Earth – 4,000,000,000 years ago sheets from today (22 sheets from the Earth’s origin)
Formation of Earth – 4,600,000,000 years ago
end of the roll of paper!

16. Reflection Complete an exit slip answering the following prompts:
Today I learned for the first time that…
This makes me think about…
Now I am curious to know…