Which geologic principle states that if rock strata are found folded or faulted, the folding or faulting occurred after they were deposited?
faunal succession
uniformitarianism
original horizontality
cross-cutting relationships
Uniformitarianism does not sound right at all for this, and neither does faunal succession, so I'm stuck between original horizontality and cross-cutting relationships.
It seems to be asking about the original state.
faunal successsion
The answer is original horizontality. I found it on Quizlet.
The geologic principle that states that if rock strata are found folded or faulted, the folding or faulting occurred after they were deposited is called the principle of cross-cutting relationships.
To understand this principle, you first need to know the concept of superposition. The principle of superposition states that in an undisturbed sequence of rock layers, each layer is younger than the one beneath it and older than the one above it.
Now, let's consider the other option, original horizontality. The principle of original horizontality states that sedimentary rock layers are originally deposited in horizontal or nearly horizontal layers. However, due to tectonic forces or other geological processes, these layers can become tilted, folded, or faulted.
So how do we differentiate between original horizontality and cross-cutting relationships in this case? When we find folded or faulted rock layers, the key is to observe the relationship between these deformed layers and other features, such as faults or igneous intrusions. If the folded or faulted rock layers are cut by another feature like a fault or an igneous intrusion, then the principle of cross-cutting relationships applies.
Therefore, in your case, the correct answer is cross-cutting relationships. It suggests that the folding or faulting happened after the deposition of the rock layers and was caused by geological forces that deformed the pre-existing layers.