Problem Analysis:
The task involves using principles of
relative dating to determine the age relationships between rock layers in two cross-section diagrams. Relative dating relies on observable geological relationships rather than absolute ages. The key principles include:
1.
Principle of Superposition: In an undisturbed sequence of sedimentary rocks, the oldest layer is at the bottom, and the youngest is at the top.
2.
Principle of Cross-Cutting Relationships: A feature that cuts across another is younger than the feature it cuts.
3.
Principle of Inclusions: If one rock contains fragments of another, the fragments are older than the rock that contains them.
4.
Principle of Original Horizontality: Sedimentary rocks are initially deposited horizontally. Deviations from this indicate later deformation.
Solution for Question 7:
#### Diagram (Left Cross-Section):
We need to identify which bed is older for each pair of rock layers using relative dating principles.
1.
A & B:
- Bed
A is a sedimentary layer, and bed
B is granite (igneous intrusion).
- Granite
B cuts through sedimentary layer
A, indicating that
B is younger than
A.
-
Older bed:
A.
2.
C & D:
- Both
C and
D are sedimentary layers.
- According to the principle of superposition,
D is below
C, so
D is older.
-
Older bed:
D.
3.
D & E:
- Bed
E is a fault line, and bed
D is a sedimentary layer.
- Faults typically form after the deposition of sedimentary layers. Therefore,
D is older than
E.
-
Older bed:
D.
4.
J & K:
- Both
J and
K are sedimentary layers.
- According to the principle of superposition,
J is below
K, so
J is older.
-
Older bed:
J.
Final Answers for Question 7:
-
A & B:
A
-
C & D:
D
-
D & E:
D
-
J & K:
J
---
Solution for Question 8:
#### Diagram (Right Cross-Section):
We need to identify which bed is younger for each pair of rock layers using relative dating principles.
1.
M & A:
- Bed
M is a sedimentary layer, and bed
A is also a sedimentary layer.
- According to the principle of superposition,
M is above
A, so
M is younger.
-
Younger bed:
M.
2.
J & N:
- Bed
J is a sedimentary layer, and bed
N is a fault line.
- Faults typically form after the deposition of sedimentary layers. Therefore,
N is younger than
J.
-
Younger bed:
N.
3.
H & C:
- Bed
H is a sedimentary layer, and bed
C is a sedimentary layer.
- According to the principle of superposition,
C is above
H, so
C is younger.
-
Younger bed:
C.
4.
D & M:
- Bed
D is a sedimentary layer, and bed
M is a sedimentary layer.
- According to the principle of superposition,
M is above
D, so
M is younger.
-
Younger bed:
M.
Final Answers for Question 8:
-
M & A:
M
-
J & N:
N
-
H & C:
C
-
D & M:
M
---
Final Answer:
\[
\boxed{
\begin{array}{ll}
\text{Question 7:} & \text{A & B: A, C & D: D, D & E: D, J & K: J} \\
\text{Question 8:} & \text{M & A: M, J & N: N, H & C: C, D & M: M}
\end{array}
}
\]
Parent Tip: Review the logic above to help your child master the concept of rock layers worksheet.
