Question

Which among the following is the only possible plunge for a lineation located on the foliation plane striking 20° N and dipping 40° southeasterly?

• A. 20° SE
• B. 20° NW
• C. 45° SE
• D. 40° NW

Hint:

The plunge direction of any lineation on a planar surface must align with or be parallel to the dip direction of that plane.

Answer 1

The Correct Option is A

Step 1: Interpreting the strike and dip.
The foliation plane strikes 20° N and dips 40° towards the southeast. This means the plane inclines downward to the southeast direction.
Step 2: Possible plunge direction.
Any lineation lying on this plane must plunge in the same general direction as the dip — that is, toward the SE. Therefore, only SE-directed plunges are possible.
Step 3: Comparing the options.
Among the given choices, 20° SE is the only plunge that fits both the orientation and the dip of 40°.
Step 4: Conclusion.
Hence, the correct answer is (A) 20° SE.