Question

which statement below best describes the undisturbed sedimentary layers? the geologic principle of superposition indicates that layer 1 is younger than layer 4. the geologic principle of faunal succession indicates that fossils found in layer 3 must be must be younger than fossils found in layer 2. the geologic principle of original horizontality indicates that all of the layers did not form in flat horizontal layers. the geologic principle of cross cutting relationships indicates that layer 3 was intruded into layer 4

Explanation:

1. Analyze the first option: The principle of superposition states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest at the top. So layer 1 (topmost) is younger than layer 4 (deeper), which matches this principle.
2. Analyze the second option: Faunal succession deals with fossil assemblages changing over time, but layer 3 is below layer 2 (assuming layer numbering from top as 1, 2, 3, 4), so fossils in layer 3 should be older than in layer 2, so this is incorrect.
3. Analyze the third option: Original horizontality states that sedimentary layers are initially deposited horizontally. The layers here look horizontal, so this statement misinterprets the principle.
4. Analyze the fourth option: Cross - cutting relationships apply to features that cut through layers (like faults or intrusions). Layer 3 and 4 seem to be sedimentary layers with 3 above 4, not an intrusion, so this is incorrect.

Answer:

The geologic principle of superposition indicates that layer 1 is younger than layer 4.