🪔 SHUBH DIVALI 2025! 🪔

Waves

Anatomy, Types

Edu Level: Unit1

Date: Sep 6 2025 - 4:37 AM

⏱️Read Time: 3 min

Crest: The highest point of a wave above the still-water level.
Trough: The lowest point of a wave below the still-water level.
Wave Height: The vertical distance between the crest and the trough.
Wavelength: The horizontal distance between two successive crests or troughs.
Wave Period: The time it takes for two consecutive wave crests to pass a fixed point.
Example: If you start timing when one crest passes and stop when the next crest passes, that interval is the wave period.
Wave Frequency: The number of waves passing a specific point within a given time frame.

Other related terms:

Swash: The forward movement of water up a beach after a wave breaks.
Backwash: The return flow of water back toward the sea after swash.
Fetch: The uninterrupted distance over which wind blows across open water to generate waves.

Wave action is a major force shaping coastlines. The energy a wave possesses depends on:

Waves develop when wind transfers energy to the ocean surface (excluding tsunamis, which have a different origin).

Waves in Deep Water (Waves of Oscillation):
These waves appear to move forward, but water particles actually move in circular orbits, passing energy rather than mass.
Waves Approaching Shore (Waves of Translation):
As waves move into shallower water, the base encounters the seabed, creating friction that slows the wave’s base while the crest continues moving forward. This shortens the wavelength and increases wave height, eventually forming a breaker.
After breaking, the swash moves up the beach until friction and slope reduce its speed. Gravity then pulls water back as the backwash.

Two main types of wave translation affect coastlines:

Low wave frequency (around 6–8 per minute)
Form over gently sloping seabeds
Generated far offshore, carrying long-fetch energy
Gentle slopes produce spilling breakers with elliptical water motion
Strong swash transports material up the beach
Because the backwash drains away before the next wave arrives, deposition dominates, building up the beach

High wave frequency (12–14 per minute)
Typically generated by local winds
Steep nearshore slopes cause rapid friction, producing plunging breakers with circular water motion
Powerful backwash removes beach material, making these waves highly erosive
Energy is directed downward and seaward, scouring the beach

Usually formed by distant storms with strong winds.
They develop over a long fetch.
Their wavelength is long, often up to 100 m.
They have a high and steep wave height.
These waves move quickly and lose very little energy as they approach the coast.
They create spilling breakers.
Energy is dissipated over a long distance.
Typically associated with wide, flat beaches.