An unconformity is defined as?

• A. A surface representing equal erosion and deposition
• B. A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
• C. A tectonic tilting event
• D. A volcanic intrusion

Answer: (B)

An unconformity is a surface in the geologic record that marks a missing interval of time, created when erosion removes previously deposited rocks or when deposition stops for a long period. This hiatus means the rocks on opposite sides of the surface are not directly in time with each other, signaling an incomplete record. The description captures that key idea of a time gap, rather than simply describing tilting, intrusion, or a balance of erosion and deposition.