Question

which statement explains one reason why unconformities occur?
rocks along a fault break and move.
igneous rock forms at earths surface.
no sediment is deposited over a long time.
igneous rock forms between sedimentary layers.

Explanation:

Unconformities are gaps in the geological record. When no sediment is deposited over a long time, it creates a break in the rock layers (an unconformity). Faults (rocks along a fault break and move) are related to fractures and displacement, not directly to unconformities. Igneous rock forming at Earth’s surface or between sedimentary layers doesn’t explain the gap (unconformity) caused by lack of sediment deposition.

Answer:

No sediment is deposited over a long time.