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14.5: Activity 14D - Applying Numeric Dating

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    1. If a rock begins with 4000 atoms of a radioactive isotope, how many would remain

    a. after one half-life?

    b. after two half-lives?

    c. after three half-lives?

    d. after four half-lives?

    2. If an isotope has a half-life of twenty million years, and there is 25% of the isotope remaining in a rock, how old is the rock?

    a. 10 million years

    b. 20 million years

    c. 40 million years

    d. 60 million years

    3. A scientist radiometrically dates 3 different rocks using 3 separate decay series. If each rock contains 50% of their measured radioactive element and 50% of its corresponding daughter element, which rock is oldest?

    Rock A is dated using isotope A (half-life = 50 years)

    Rock B is dated using isotope B (half-life = 100 years),

    Rock C is dated using isotope C (half-life = 1000 years).

    a. Rock A

    b. Rock B

    c. Rock C

    d. Impossible to tell

    4. An Archeologist finds some cotton cloth at a burial site and wants to determine the age of the remains. Which isotopic system should they use?

    a. Carbon-14

    b. Uranium

    c. Potassium-Argon

    5. The Archeologist determines that there is 16.7% of the parent isotope remaining in the cloth sample. How old is the burial site? Hint: you can find the length of the half-life in the reading above.

    a. 13,559 years

    b. 14,798 years

    c. 16,743 years

    d. 1.66 billion years

    e. 1.81 billion years

    f. 2.05 billion

    6. A geologist is trying to date a sequence of sedimentary rocks with abundant fossils and sandstones. Within the sequence is a distinctive clay layer that, under closer inspection, turns out to be fine-grained volcanic ash. Which of the following is the best way to obtain a numeric date for the sequence of rocks?

    a. Carbon date the fossils

    b. Potassium-Argon date the sands

    c. Uranium date the Zircons in the ash

    d. Identify the index fossils

    7. The geologist determines there is 78.3% of the parent remaining in the sample that they examine. How old is the sequence of rocks? Hint: you can find the length of the half-life in the reading above.

    a. 187.5 million years

    b. 247.8 million years

    c. 390.7 million years

    d. 2.504 billion years

    e. 1.588 billion years

    f. 1.202 billion years

    This page titled 14.5: Activity 14D - Applying Numeric Dating is shared under a not declared license and was authored, remixed, and/or curated by Chloe Branciforte & Emily Haddad (ASCCC Open Educational Resources Initiative) .

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