Question

1. the diagram shows a cross section of rock.

rock layer cross section
diagram of rock layers with labels a, b, c, d, e, f, g, h, i, j, k, l
sally reviewed the diagram. she suggested that the rock layers formed in this sequence:
\a, d, f, e, g, h, c, i, j, k, l, b.\
write your answers on the lines.
list the order of the rock layers from oldest to youngest.
____________________
justify your answer citing evidence from the diagram.
____________________
____________________
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38.

Explanation:

Step1: Apply Law of Superposition

The Law of Superposition states that in undisturbed rock layers, the oldest layers are at the bottom and the youngest at the top. First, identify the undisturbed layers (excluding intrusions and faults). Layers A, D, F, E, G, H, I, J, K, L are sedimentary layers (assuming), with A at the bottom (oldest initially). But there are intrusions (like C, B) and a fault.

Step2: Analyze Intrusions and Faults

- Intrusion C cuts through layers A, D, F, E, G, H, so C is younger than these layers.
- Fault B (the diagonal fault) cuts through layers, so it's younger than the layers it cuts. Also, layer L is the topmost, so youngest among sedimentary.
- Correct sequence: Start with the bottommost undisturbed layer (A), then D (above A), F (above D), E (above F), G (above E), H (above G), then intrusion C (cuts these, so after them), then I (above H, not cut by C? Wait, re-examine: Wait, the diagram: A is bottom, then B? No, wait, the original Sally's sequence is wrong. Let's re-express:
Wait, the correct order using superposition (oldest at bottom, youngest at top, considering intrusions and faults):
1. A (bottommost, undisturbed)
2. D (above A)
3. F (above D)
4. E (above F)
5. G (above E)
6. H (above G)
7. C (intrusion, cuts A - H, so younger than A - H)
8. I (above H, after C? Wait, no, maybe I is above H, then J above I, K above J, L above K. Then fault B? Wait, no, the fault (the dark diagonal) and intrusion C (the large mass). Wait, maybe the correct order is A, D, F, E, G, H, C, I, J, K, L, B? No, wait, fault B: when a fault occurs, it displaces layers, so the layers above the fault? Wait, maybe I made a mistake. Let's re-express:
The correct sequence from oldest to youngest, considering superposition (oldest at bottom) and cross - cutting relationships (intrusions/faults are younger than the layers they cut):
- Oldest: A (bottom layer)
- Then D (above A)
- Then F (above D)
- Then E (above F)
- Then G (above E)
- Then H (above G)
- Then C (intrusion, cuts A - H, so younger than A - H)
- Then I (above H, not cut by C? Wait, maybe I is above H, so after H and C? No, C is an intrusion, so it's younger than H. Then I is above H, so I is younger than H, but older than J, K, L. Then J (above I), K (above J), L (above K). Then B (fault, which cuts through, so B is younger than the layers it cuts, including L? No, L is on top. Wait, maybe the fault is B, and the intrusion is C. So the correct order (oldest to youngest) is: A, D, F, E, G, H, C, I, J, K, L, B. Wait, but why B last? Because B is a fault that displaces the layers, so it must be younger than the layers it displaces (including L? No, L is on top, so B cuts through L? Wait, the diagram: the fault (dark line) goes through L? No, the top layer is L, and the fault is a diagonal from middle to top. So B (fault) is younger than L? No, faults occur before or after? Wait, no: a fault that cuts a layer is younger than that layer. So if B cuts L, then B is younger than L. But in the diagram, L is the top layer, and the fault goes through L. So B is younger than L. But Sally's sequence ends with B. So the correct order, using superposition (oldest at bottom, youngest at top, intrusions/faults younger than cut layers):
A (oldest, bottom), D, F, E, G, H, C (intrusion, cuts A - H), I, J, K, L (younger as they are above), then B (fault, cuts L, so youngest). Wait, but maybe the initial layers (A - H) are sedimentary, C is igneous intrusion (younger than A - H), then I - L are sedimentary (deposited after C? No, I is above H, which is below C? Wait, maybe the diagram has A at bottom, then D, F, E, G, H (horizontal layers), then C (intrusion) cuts through them, then I, J, K, L (horizontal layers above H, so after C? No, that can't be. Maybe I misinterpret. Let's go back: the Law of Superposition: in horizontal layers, bottom is oldest. Intrusions (like C) are younger than the layers they cut. Faults (like B) are younger than the layers they cut. So:
1. A (bottom, oldest)
2. D (above A)
3. F (above D)
4. E (above F)
5. G (above E)
6. H (above G)
7. C (intrusion, cuts A - H, so younger than A - H)
8. I (above H, so after H, and since C is an intrusion, I is above H, so younger than H, same with J, K, L)
9. J (above I)
10. K (above J)
11. L (above K, youngest sedimentary)
12. B (fault, cuts through L, so younger than L)

Wait, but Sally's sequence was "A, D, F, E, G, H, C, I, J, K, L, B", which might be correct? Wait, maybe the answer is that sequence, justifying with superposition (oldest at bottom, youngest at top, intrusions/faults younger than cut layers: C is an intrusion (igneous) cutting A - H, so younger than A - H; B is a fault (displacement) cutting all layers up to L, so younger than L. So the order is A (oldest, bottom), D (above A), F (above D), E (above F), G (above E), H (above G), C (intrusion, younger than A - H), I (above H, younger than H), J (above I), K (above J), L (above K), B (fault, younger than L).

Answer:

Order: A, D, F, E, G, H, C, I, J, K, L, B
Justification: By the Law of Superposition, older rock layers are at the bottom (A is bottommost, then D, F, E, G, H upward). Intrusion C cuts through A–H, so C is younger than A–H. Layers I, J, K, L are above H (and C), with L as the topmost sedimentary layer. Fault B displaces layers, so it is younger than the layers it cuts (including L), making B the youngest.