Question

3. Based on the information obtained from your calculations, how much Uranium-235 would be left if the fossil were approximately 350 million years old? (10 points)approximately 0 mg
approximately 27 mg
approximately 40 mg
approximately 57 mg

4. Based on the information obtained from your calculations, how much Uranium-235 would be left if the fossil were approximately 1.4 billion years old? (10 points)approximately 20 mg
approximately 27 mg
approximately 40 mg
approximately 57 mg

5. To what geologic time frame do the fossils from Thomas Farm belong? (10 points)Pliocene
Mi

Answer 1

5. To what geologic time frame do the fossils from Thomas Farm belong? (10 points)Pliocene
Miocene
Oligocene
Eocene

6. What determines which specific atoms of a radioactive material decay over a period of time? (10 points)Age of the atoms; the oldest atoms decay first.
Concentration; atoms that are closely grouped decay faster than atoms that are more spread out.
Concentration; atoms that are more spread out decay faster than atoms that are closely grouped. together.
Nothing; radioactive decay of a specific atom is believed to be a completely random event.

7. Which of the following is NOT a form of absolute dating? (10 points)counting the rings of a tree to determine the age of a geologic event
counting coral growth cycles to determine the age of a geologic event
counting layers of soil in a river bed to determine the age of a geologic event
counting the decay of radioactive atoms in a sample to determine the age of a geologic event

Answer 2

8. Half-life is half the time it takes for a radioactive sample to completely decay. (10 points)True
False

9. During the radioactive decay process, the sum of the parent element material and the daughter element material always equals the original amount of parent element material regardless of how much time passes. (10 points)True
False

10. Half-life is the time it takes for half of a sample of radioactive atoms to decay. (10 points)True
False


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Answer 3

1. Visit the following website to learn about Thomas Farm, which is a place in Florida where many of these types of horse fossils have been found: http://www.flmnh.ufl.edu/fossilhall/FLPaleo/ThomasFarm/ThomasFarm.htm
Use the Thomas Farm website to answer this question:

•To what geologic time frame do the fossils from Thomas Farm belong?
•What age do you estimate the fossil to be?

2. Use the information above and what you have learned about radiometric dating to determine the approximate age of the horse fossil. You may find that this radiometric dating calculator tool is useful: http://www.hartnell.cc.ca.us/faculty/scharnic/practice/radioactivedecaycalculator.html

Note: The calculator allows you to input a half-life value, a beginning element amount (hint: it is more than 78.59mg!), and a time frame (which is the same as the fossil's age estimate). It will then tell you how much of the element would remain after the set amount of time has passed. As you change the amount of time, you'll see that the amount of remaining element changes as well. Experiment with the age of the fossil until you get a value for the remainder of the element that matches what is in our sample. At that point, you'll have discovered the age of the fossil!

3. Continue to experiment with the calculator to get the answers to the following questions:
(Hint: Remember that the half life of U-235 is 700 million years. Use the sample chart on the lesson page to help you if you get stuck.)

•How much Uranium-235 would be left if the fossil were 700 million years old?
•How much Uranium-235 would be left if the fossil were only 350 million years old?
•How much Uranium-235 would be left if the fossil were 1.4 billion (1,400,000,000) years old?

Answer 4

Radiometric dating explained:

http://en.wikipedia.org/wiki/Radiometric_dating

http://pubs.usgs.gov/gip/geotime/radiometric.html

Half-life and radioactive decay graphic demo:

Slide the button to simulate the passage of time, and watch the values of the elements change: http://sciencecourseware.com/VirtualDating/files/2.0_HalfLife.html

Full tutorial on radioactive decay and radiometric dating:

With interactivities and self-check quizzes: http://sciencecourseware.com/VirtualDating/files/1.0_ClocksInRocks.html

Radiometric calculators:

Basic: http://www.hartnell.cc.ca.us/faculty/scharnic/practice/radioactivedecaycalculator.html

Better: http://www.1728.com/halflife.htm

More advanced: http://www.nih.gov/od/ors/ds/rsb/raddkcalc/calcframe.htm

Carbon-dating calculator: http://www.101science.com/Carbon14.htm