Question

in which situation is the principle of cross - cutting relationships useful in determining relative age?
○ a fault breaks through sedimentary layers.
○ fossils of two different species are found in different rock layers.
○ sedimentary layers form over millions of years in a lake bottom.
○ lava flows form on top of one another from several eruptions over time.

Explanation:

The principle of cross - cutting relationships states that a geological feature (like a fault) that cuts through another geological feature (like sedimentary layers) is younger than the feature it cuts through.

• For option A: A fault breaking through sedimentary layers is a classic example of cross - cutting relationships. The fault is younger than the sedimentary layers it cuts, so this principle can be used to determine relative age.
• For option B: Finding fossils of different species in different rock layers is related to the principle of fossil succession, not cross - cutting relationships.
• For option C: The formation of sedimentary layers over time in a lake bottom is related to the principle of superposition (older layers at the bottom, younger at the top) in a simple depositional context, not cross - cutting.
• For option D: Lava flows forming on top of one another is related to the principle of superposition (the lower lava flow is older, the upper is younger) as they are deposited one on top of the other, not cross - cutting.

Answer:

A. A fault breaks through sedimentary layers.