Learning from absolute
dating
pg 8 in TOC
Warm-up
• In your own words define relative dating.
Include an example.
• Today we are going to focus on absolute
dating. Using context clues, create a
definition for absolute dating and also
provide an example.
Recap: Relative Dating
• Used in geology to determine the order of events in relation
to other events.
• This doesn’t say anything about the exact age of rock layers or
fossil remains
• Known as the law of superposition
• What is radioactive decay?
• What does it mean when something is stable or
unstable?
• What are some ways we use radioactive things?
• http://www.youtube.com/watch?v=bLszCCLN-uw
So what is Radioactive Decay?
• Some atoms are unstable and breakdown over
time in another more stable form. This process is
called radioactivity
• The rate of change or breakdown of elements is
measured in Half-lives.
• Stable = not decayed
• Unstable= decayed
• The method used to determine absolute age of
rock or fossil
A look at half lives:
a half-life is the amount of time it takes for
something to divide in half
Testing out absolute dating
• Problem:
How many half-lives does it take Rock X to turn
into Rock Y
Hypothesis:
Materials:
Beans, container with lid
Create a graph like this in your
notebook
Trials
# beans white side
up
Testing out absolute dating
• In this lab you are going to start with 100 beans. The
beans represent fossil X atoms. For this lab you will
model how radioactive dating works.
• Count your atoms and make sure you have 100
• Place them in the box with all them on the white facing
side.
• Close the lid and shake the box
• Open the box and count the atoms that have the red side
up. After you finish remove them from the box and graph
your white side up results.
• Repeat steps 3 and 4 until you get down to 1 or 0.
Bean Decay lab Questions
1. Was your hypothesis correct? Explain.
2. In this lab our trials stands for ___________
3. At the end of each trial , approximately what percentage are the
atoms “decaying”?
4. Does the amount of time you shake the box affect the outcome?
Explain.
5. Do the number of atoms you start with affect the outcome?
Explain. For example if we only used 50 beans, would my data
be different. Think about this and explain your answer. Include
data and other info to support answer.
6. Relative dating is to law of superposition as absolute dating is to
___________
7. How do you think absolute dating differs from relative dating?
8. How would absolute dating support the theory that the Earth is
old? Explain and use vocabulary terms
Look at the class master graph…
• Why doesn’t everyone have the same results?
• What can this tell us about the accuracy of half
lives?
Try this
• If Carbon-14 has the half-life of
5730 years, after 11,400 years
approximately how many half
lives would Carbon of gone
through?
Try This!!
•If an element was found
with 100 atoms of
Carbon, which has a half
life of 5730 years; how
much will be left after 3
half lives?
Ticket out the door
1. How do scientists use radioactive decay or absolute age to
date fossils and artifacts?
2. How accurate do you think absolute dating would be? Give
me a time frame.