Transcript Geologic Time - Ms. George`s Science Class

Geologic Time
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.
4.6 billion years!
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.
4,600,000,000 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?
• 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.
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.
1 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?
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)
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
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
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 365.25 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
• 4,600,000,000 seconds  31,600,000
seconds/year =
• That’s almost 145 years!
• Remember, your own lifetime can be
clapped in less than 15 seconds!
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
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.
•
•
•
•
•
•
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. 2.5 sheets from today
First bird fossils formed – 174,000,000 years
ago. 6.7 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
• Abundant shell life = 542,000,000 years ago
21 sheets from today
• Oxygen occurs in Earth’s atmosphere –
2,000,000,000 years ago. 76 sheets from today
• First life forms (prokaryotes) – 3,600,000,000
years ago 138 sheets from today
• Oldest rocks on Earth – 4,000,000,000 years
ago. 154 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!
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…