CPG Structural Geology & Tectonics Flashcards

The San Andreas Fault in California is best classified as what type of fault?

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.

A horst is best defined as:

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.

The Rio Grande Rift in New Mexico is an example of which tectonic feature?

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.

Foliation in metamorphic rocks is primarily created by:

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.

Which structural feature places older rocks stratigraphically above younger rocks?

Answer: A thrust fault

Thrust faults transport older rocks over younger rocks, inverting the normal stratigraphic order across the fault plane.

The Wilson Cycle in plate tectonics describes:

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.