Geology Assignment: Calculating Radiometric Ages of Rocks and Determining Relative Ages

Answer the following questions. To receive full credit, you must provide accurate answers to the questions. [Scroll down to read the grading scheme (rubric)].

1. A hypothetical rock is going to be analyzed for its radioactive isotope contents, X and Y. X is the parent and Y is the daughter isotope. Assume that the half-life of the radioactive isotopes is 10,000 years. Based on this information, answer the following two questions.

A) How much of the parent (X) and how much of the daughter (Y) will be present at the time the rock forms? You can give your answer in % as follows: (12 points)

X = 100% ; Y = 0%

B) How much of the parent (X) and how much of the daughter (Y) will be present after 10,000 years? You can give your answer in %. as follows: (13 points)

X = 50% ; Y = 50%

2. The accompanying diagram is a cross section of a hypothetical area. Place the lettered features in the proper sequence, from oldest to youngest. (25 points)

[ Hint: “Lava flow I” is the youngest rock because it cuts across all other rocks; “A” is the oldest because it is underneath all other rocks.

Note: You don’t need to write the reason as I did above, this was meant to explain to you the reason why “I” is the youngest and “A” is the oldest. You just need to place the letters, as indicated at the bottom of the figure ] (I have attached the figure called Figure 1)

Figure 1 (Look at figure 1 for the following)

A, B, C, D, E, L, K, M, F, G, J, H, I

Dike L precedes Pluton K because K covers L. M follows K because M covers K, all of which were covered by F. Fault J precedes H because H filled level above the fault after it formed, and finally Lava flow I is the youngest, atop all the others.

I also am posting the grading rubric below:

This criterion is linked to a Learning Outcome Quality of content and adherence to instructions on paragraph/sentence length

50.0 pts

Exemplary

Post includes valid and adequate answers for all questions. The arguments made are thorough, well thought out and are supported by course materials or outside resources; strictly followed instructions on paragraph/sentence length.

40.0 pts

Accomplished

Post includes valid answers for most questions. The arguments made are solid and are generally supported by course materials or outside resources; may have not followed instructions on paragraph/sentence length &/or left out one question unanswered.

20.0 pts

Developing

The post includes answers to no more than 1 question; answers are clear and adequate; the arguments made are clearly related to the topic prompt and are supported by credible references; instructions on paragraph/sentence length may not have been followed.

10.0 pts

Needs to Improve

The post provides answers to no more than 1 question and is not adequately discussed; did not follow instructions on paragraph/sentence length; indications of little or minimal effort.

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