CPG CPG Structural Geology & Tectonics 2 — Questions and Answers
Question 1: The San Andreas Fault in California is best classified as what type of fault?
- Normal fault
- Reverse fault
- Right-lateral strike-slip fault (Correct answer)
- Left-lateral strike-slip fault
Correct answer: Right-lateral strike-slip fault
The San Andreas is a right-lateral strike-slip fault; an observer on either side sees the opposite block move to the right.
Question 2: A horst is best defined as:
- A down-dropped block between two normal faults
- An uplifted block bounded by two normal faults (Correct answer)
- A type of recumbent fold
- A shallow volcanic intrusion
Correct answer: An uplifted block bounded by two normal faults
A horst is an elevated crustal block bounded on both sides by normal faults, forming a ridge or plateau.
Question 3: The Rio Grande Rift in New Mexico is an example of which tectonic feature?
- A convergent plate boundary
- A transform fault zone
- A continental extensional rift (Correct answer)
- A thin-skinned thrust belt
Correct answer: A continental extensional rift
The Rio Grande Rift is an active continental rift zone where the crust is being pulled apart, forming a series of north-trending grabens.
Question 4: Foliation in metamorphic rocks is primarily created by:
- Chemical weathering along bedding planes
- Hydrothermal alteration
- Directed (non-hydrostatic) stress during metamorphism (Correct answer)
- Igneous intrusion contact effects
Correct answer: Directed (non-hydrostatic) stress during metamorphism
Foliation develops when directed stress causes platy or elongate minerals to recrystallize perpendicular to the maximum compressive stress.
Question 5: Which structural feature places older rocks stratigraphically above younger rocks?
- A normal anticline
- An overturned fold limb
- A thrust fault (Correct answer)
- A high-angle normal fault
Correct answer: A thrust fault
Thrust faults transport older rocks over younger rocks, inverting the normal stratigraphic order across the fault plane.
Question 6: The Wilson Cycle in plate tectonics describes:
- Seasonal fluctuations in mid-ocean ridge magma output
- The repeated opening and closing of ocean basins (Correct answer)
- Cyclical erosion and uplift of continental mountain ranges
- Glacial advance and retreat driven by orbital cycles
Correct answer: The repeated opening and closing of ocean basins
The Wilson Cycle describes the sequence from continental rifting, ocean opening, subduction, and eventual continental collision that closes the ocean basin.
CPG CPG Structural Geology & Tectonics 2
The San Andreas Fault in California is best classified as what type of fault?