How Beaches Form and Why They Differ

Formation Process

1. Erosion & Sediment Supply: Waves, rivers, cliff collapse produce sand, gravel, cobbles.
2. Longshore Drift: Oblique waves move sediment alongshore in a zigzag.
3. Deposition & Sorting: Sediment accumulates where energy drops; waves sort by size/density.
4. Morphodynamic Equilibrium: Profile adjusts to wave climate—steep for coarse/reflective, flat for fine/dissipative.

Why Beaches Vary

• Sediment Source: Quartz (white), basalt (black), coral (pink/white), olivine (green), shells.
• Wave Energy: High energy → coarse, steep; low energy → fine, flat.
• Tidal Range: Macrotidal → wide, flat; microtidal → narrow, steep.
• Geologic Framework: Bedrock resistance, coastal structure control sediment supply and shape.
• Human Modification: Groynes, jetties, nourishment, mining alter natural patterns.

Every beach is a unique fingerprint of its geologic and oceanographic history.