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

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