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 rock record due to erosion or lack of sediment deposition.
• "Rocks along a fault break and move" relates to faulting, not unconformities.
• "Igneous rock forms at Earth’s surface" (extrusive igneous rock) doesn’t explain unconformities.
• "Igneous rock forms between sedimentary layers" is intrusive igneous activity (like sills), not related to unconformities.
• "No sediment is deposited over a long time" creates a gap (unconformity) as sedimentary deposition is interrupted, matching the cause of unconformities.

Answer:

C. No sediment is deposited over a long time.