Geologic Time

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Geologic Time
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Our Planets History

• Geologic time is the time frame of our planets
  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!

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How do Scientists Know the Earths 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.

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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?

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• 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.

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Activity 1 Clapping the Earths Life

• Lets 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?

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• 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)

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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

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How long would it take to clap the Earths Age,
4.6 billion years?

• Do you think you could clap the Earths Age in
  your own lifetime? Circle one.
• YES NO

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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

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• 4,600,000,000 seconds ? 31,600,000 seconds/year
• Thats almost 145 years!
• Remember, your own lifetime can be clapped in
  less than 15 seconds!

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Activity 2 TP Timeline

• Now we are going to make a TP Timeline!
• The tissue were using contains 176 sheets per
  roll.
• The entire roll represents the earths 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

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Major Earth Events

• We are going to label the tissue timeline to mark
  significant events in the Earths history.
• Well start from today and work backward in time.

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• TP Timeline
• Early modern humans 130,000 years ago. Thats
  0.5 of one sheet from today (the edge of the
  first sheet)
• The first hominids 7,000,000 years ago27 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 ago9.4
  sheets from today
• First fish, first insects 490,000,000 years
  ago18.8 sheets from today

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• Abundant shell life 542,000,000 years ago21
  sheets from today
• Oxygen occurs in Earths 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 Earths
  origin)
• Formation of Earth 4,600,000,000 years ago
• end of the roll of paper!

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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