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Difficulty: Very hardOceans, Coastal Processes, and Coastal Landforms

During wave refraction along an irregular, indented coastline featuring alternating resistant headlands and weaker rock bays, orthogonal wave energy lines bend as water depth decreases near the shore. Which of the following correctly describes the distribution of wave energy and its resulting geomorphic effect along this coastline?

  1. Wave energy converges on headlands causing intensified erosion, while wave energy diverges within bays leading to sediment deposition.Answer
  2. B
    Wave energy concentrates at the head of shallow bays to carve out steep upper-course river valleys and oxbow lakes.
  3. C
    Wave energy causes in-situ chemical decomposition of headland rocks without physical detachment or transportation of coastal sediments.
  4. D
    Wave energy subjects bay sediments to extreme thermal pressure, metamorphosing loose beach sand directly into slate bedrock.

Answer

Wave energy converges on headlands causing intensified erosion, while wave energy diverges within bays leading to sediment deposition.
As deep-water waves approach an indented coastline, the section of the wave front off headlands enters shallow water first and slows down due to bottom friction. This causes the wave crests to bend (refract), concentrating wave orthogonals and energy onto the headlands, which drives high rates of hydraulic erosion. Conversely, in the deeper water of bays, the wave energy diverges over a wider area, creating low-energy environment suitable for sediment deposition and beach formation.

Step-by-Step Solution

1
Analyze the mechanics of wave refraction along an indented coastline.
Waves drag on the shallow seabed in front of headlands first, slowing down while the deeper parts of the wave front in bay areas continue moving faster.
Friction with the sea floor decreases wave speed in shallow water near headlands.
2
Determine the direction of wave orthogonals (energy paths).
Wave rays bend toward the headlands, causing energy lines to converge on headlands and spread out (diverge) inside bays.
Wave refraction redirects wave energy perpendicular to the shoreline contours.
3
Correlate energy concentration with geomorphic coastal features.
Convergence at headlands leads to high-energy destructive wave action (forming cliffs, caves, arches), while divergence in bays results in low-energy constructive wave action (forming beaches).
High energy density accelerates marine erosion, whereas low energy density promotes sediment deposition.

Key Concept

Wave Refraction and Coastal Energy Distribution
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Topics

Oceans, Coastal Processes, and Coastal Landforms

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