Which scenario describes a plunging wave?

• A. When the wave encounters a sudden decrease in depth such as a reef or steep rise in the ocean floor.
• B. When wave energy encounters a sloping ocean floor, the crest of white water spreads down the wave face.
• C. When waves are created on very steep beaches, the wave builds quickly and expends its energy on the beach.
• D. When a wave travels long distances without breaking.

Answer: (A)

A plunging wave forms when a wave moving into shallow water suddenly encounters a sharp depth change, causing the crest to outrun the rest of the wave and curl over as it breaks. This happens most clearly over features like a reef or a steep rise in the ocean floor, where the rapid change steepens the wave and makes the crest dive downward into a hollow tube. That curl and forceful crash characterize plunging breakers.

The other scenarios describe different breaker styles. A wave meeting a sloping bottom tends to spill its energy down the face rather than curl, producing a spilling breaker. Very steep beaches cause waves to break directly on the shore in a beach break. Waves that travel long distances without breaking are non-breaking.