1 which principle states that the oldest rock layer is found at the bottom in an undisturbed stack of rock…

1 which principle states that the oldest rock layer is found at the bottom in an undisturbed stack of rock layers? a half - life b absolute dating c superposition d uniformitarianism 2 which term means matching up rock layers in different places? a superposition b correlation c uniformitarianism d absolute dating 3 which isotope is useful for dating wood and charcoal that is less than about 75,000 years old? a carbon - 14 b potassium - 40 c uranium - 238 d argon - 40 4 a substance at 1 half - life has 50 percent of a parent isotope remaining. what percentage of the parent isotope remains at 2 half - lives? a 6.25 percent b 25 percent c 3.125 percent d 1.07 percent 5 which principle states that the same processes at work in earth’s past are still at work today? a deposition b superposition c unconformity d uniformitarianism the table below shows the percent remaining parent isotope per half - life of a radioisotope. use the table to answer questions 6 and 7. number of half - lives parent isotope remaining (%) 1 100 2 x 3 25 4 12.5 5 y 6 which percentage replaces the letter x? a 40 b 50 c 6205 d 75 7 which percentage replaces the letter y in the table above? a 0 b 2.5 c 3.13 d 6.25

1 which principle states that the oldest rock layer is found at the bottom in an undisturbed stack of rock layers? a half - life b absolute dating c superposition d uniformitarianism 2 which term means matching up rock layers in different places? a superposition b correlation c uniformitarianism d absolute dating 3 which isotope is useful for dating wood and charcoal that is less than about 75,000 years old? a carbon - 14 b potassium - 40 c uranium - 238 d argon - 40 4 a substance at 1 half - life has 50 percent of a parent isotope remaining. what percentage of the parent isotope remains at 2 half - lives? a 6.25 percent b 25 percent c 3.125 percent d 1.07 percent 5 which principle states that the same processes at work in earth’s past are still at work today? a deposition b superposition c unconformity d uniformitarianism the table below shows the percent remaining parent isotope per half - life of a radioisotope. use the table to answer questions 6 and 7. number of half - lives parent isotope remaining (%) 1 100 2 x 3 25 4 12.5 5 y 6 which percentage replaces the letter x? a 40 b 50 c 6205 d 75 7 which percentage replaces the letter y in the table above? a 0 b 2.5 c 3.13 d 6.25

Answer

Brief Explanations:

  1. In an undisturbed stack of rock layers, the principle of superposition states the oldest layer is at the bottom.
  2. Correlation means matching up rock - layers in different places.
  3. Carbon - 14 is useful for dating wood and charcoal less than about 75,000 years old.
  4. After 1 half - life, 50% of the parent isotope remains. After 2 half - lives, 25% remains (since $50%\times0.5 = 25%$).
  5. The principle that the same processes at work in Earth's past are still at work today is uniformitarianism.
  6. After 2 half - lives, if the initial amount is 100%, the remaining parent isotope is 50% of 50%, which is 25%. So X = 50.
  7. After 5 half - lives, starting from 100%, we have $100\times(0.5)^5=100\times0.03125 = 3.125\approx3.13$. So Y = 3.13.

Answer:

  1. C. superposition
  2. B. correlation
  3. A. carbon - 14
  4. B. 25 percent
  5. D. uniformitarianism
  6. B. 50
  7. C. 3.13