Absolute Dating In this part of the exercise, you will be calculating the actual
ID: 232583 • Letter: A
Question
Absolute Dating In this part of the exercise, you will be calculating the actual, or absolute, ages of the rock. The figure above shows the relationship between the percentage of parent material and the number of half-lives that have passed.
4. What percentage of the parent material is present after one half-life? Two? Three? Four?
5. If you start with 80 grams of an isotope, how much would be left after-one half-life? What about three half-lives?
6. If an isotope has a half-life of 600 million years, how old is a rock that contains the isotope after 50% of the parent has decayed? How old is the rock after four half-lives have passed?
7. You discover the parent isotope in a lava flow has gone through 0.75 half-lifes. If a half-life is 800 million years, how old is that rock?
8. In number 1, at the beginning of the exercise, Layer F was dated at 260 million years old. Layer E was determined to be 235 million years old. When did the fold occur?
9. The image to the left show a series of sections containing various fossils. If the star is 325 million years old (ma), and the heptagon (the 7-sided fossil) is 337 ma, how old is the 15-sided fossil in between? If the star existed for three million years, from 324ma-327ma, how old must the arched arrow in section three be?
10. Based on what you learned about fossil preservation, how might the following be preserved as fossils? Dinosaur bones? Microscopic organisms like bacteria and protists? Skin or feathers? DNA?
Thank you.
100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5Explanation / Answer
4. After 1 half life = 50% is left
2 half life - 25 % is left
3 half life - 12.5 % is left
4 half life - 6.25% is left
5. If you have 80 grms after 1 half life = 50% = 40gms
after 3 half life = 12.5% = 10 grms
6 . If a rock has 50% left age is half life x 2 = 1200 million years
after 4 half lifes age of rock is = 600x 4 million years = 2400 million years.
7. After 0.75 half lives - 62.5 % is left ( from the graph)
half life = 800 million years , so age of rock is 0.75 x 800 =600 million years.
8. Number 1 not present in this excersize, question starts with 4.
9. Difference is 337- 325 = 22 , so it is in between , it is in mean of the both 325 + 22/2 = 336 ma
if star existed from 324-327 , then the arched must have existed for 336 -327 = 8 years
10. Dinosour bones can be preserved in vaccum glass box as in vaccum they dont degenerate further.
Feathers and skin must be stored in a box withouht entering light in a neutral environment of ph value around 7
To store dna these are the conditions :
Microorganisms are stored in salt concentrated and low temperatures using freeze dying mechanisms