Which coastal feature forms across the mouth of a bay and may trap a lagoon behind it?

Which coastal feature forms across the mouth of a bay and may trap a lagoon behind it?

• A. Bay Mouth Bar
• B. Beach
• C. Beach Scarp
• D. Breakwater

Answer: (A)

Bay mouth bars form where waves and longshore drift move sand along the coast and deposit it across the opening of a bay. Over time this continual sediment buildup creates a continuous ridge across the mouth, effectively blocking the inlet. When the inlet is closed in this way, water exchange with the open ocean is reduced, so a shallow lagoon can develop behind the bar. This coastal feature is a natural barrier created by sediment transport, rather than a beach or a cliff-like scarp, and it’s not a man-made structure like a breakwater. The result is a barrier across the bay mouth with a possible lagoon trapped behind.

Bay mouth bars form where waves and longshore drift move sand along the coast and deposit it across the opening of a bay. Over time this continual sediment buildup creates a continuous ridge across the mouth, effectively blocking the inlet. When the inlet is closed in this way, water exchange with the open ocean is reduced, so a shallow lagoon can develop behind the bar. This coastal feature is a natural barrier created by sediment transport, rather than a beach or a cliff-like scarp, and it’s not a man-made structure like a breakwater. The result is a barrier across the bay mouth with a possible lagoon trapped behind.