#Explain to Daughter
4 messages in this thread
We were watching a special about Illinios and they talk about the Glaciers that
created the paires and gave the time. My daughter asked how they knew the
age/time? I explained the idea of layers and the time it take for a layer to
form. Can anyone help with with a better or broader answer, she is seven. She
is one to task me with some tough quetions to explain at her level since I
learned the subject in High School or College. Thank you in advance for help
with this.
Craig
Much of the dating is derived from analyzing the ratios of C12 and C14, carbon
isotopes found in organic matter. Carbon14 has a 1/2-life of 5,600 years if
memory serves. C14 is incorporated in the organism while it is living and once
biological processes stop (death), no additional C14 is picked up.
By measuring the amount of C12 and C14, it is possible to determine the age of
the organic material. Then one has the age (roughly) of the soil laying on top
of the fossil.
It can be (and usually is) much more complicated to determine the age of a
geological event such as glaciation. Often a variety of methods must be used
to establish the chronology of climatic events. Glacial, and other, lakes
often display a distinct layering of sediments called varves, in which an
alternating pattern of light and dark layers are laid down. These layers
represent seasonal patterns, essentially summer and winter. The layers can be
extremely thin. You can envision them as similar to tree rings. If you can
establish a geological time within the varves, by using an index fossil, carbon
dating, or dating volcanic ash, then you can count the "rings" and determine
the length of time the lake was in existence.
This is only a very brief description of how some dating is done. I'll be glad
to add more if you want.
Michael
Thanks Michael,
I hope I can explain this to Catherine. Easiest way
to teach is to answer question that interests them personally. I had forgatten
about the algae layers. Again Thanks.
Craig
You might want to contact the U.S. Geological Survey's Earth Science
Information Center at 1-800-USA-MAPS. They have a great booklet on geologic
time. I know that it is free if you stop in to the Information Center… I
don't know if there is any shipping/handling charge for mailing out…..
joann miller