Swell Waves Likely to Hit Coastal Areas

The swell waves, known locally as 'Kallakkadal', caused flooding in coastal areas of southern and central Kerala.

• As noted by the fishing community, this phenomenon is not common at this time of year.

 What are the Swell waves ?

1. Swell waves are a type of ocean wave that travel long distances from their origin. They are also known as ground swells.
2. Swell waves are a series of surface gravity waves that are not affected by local winds. They are caused by distant storms, hurricanes.
3. Swell waves can travel thousands of kilometers across the ocean without breaking.
4. Swell waves can be a significant factor in shaping coastal areas. When they reach the shore, they can cause erosion and inundation.

What is Kallakkadal?

1. Kallakkadal is essentially coastal flooding during the pre-monsoon (April-May) season by swell waves on the southwest coast of India.
2. The term Kallakkadal, used by local fishermen, is a combination of 2 Malayalam words, including Kallan and Kadal. “Kallan means thief and Kadal means sea.

Swell waves and P-waves and S-waves are entirely different types of waves with very distinct characteristics:

Swell Waves

1. Medium: Swell waves travel across the surface of the ocean.
2. Type of Wave: A type of mechanical wave where water particles move in a roughly circular motion.
3. Formation: They are generated by wind out in the open ocean and travel long distances.
4. Relevance: Important for surfers, coastal shaping, and ocean circulation patterns.

P-Waves and S-Waves

1. Medium: P-waves (primary waves) and S-waves (secondary waves) travel through the Earth's interior.
2. Type of Wave: Body waves, a type of seismic wave formed during earthquakes.
3. Formation: Generated by sudden shifts and ruptures within the Earth's crust.
4. Relevance: Used by scientists to study the Earth's internal structure and locate the origin of earthquakes.

Feature	Swell Waves	P-Waves	S-Waves
Medium	Ocean surface	Earth's interior	Earth's interior
Type of Wave	Surface wave (mechanical)	Body wave (compressional)	Body wave (shear)
Motion of Particles	Circular	Compressions and expansions (longitudinal)	Side-to-side motion (transverse)
Speed	Relatively slow	Fastest seismic wave	Slower than P-waves
Travel through liquids	Yes	Yes	No

What are P-waves and S-waves ?

• P-waves and S-waves are types of seismic waves, the energy waves released during an earthquake or volcanic eruption.

P-waves (Primary Waves)

P-waves, also known as primary or compressional waves, are the fastest seismic waves and travel in the same direction as the ground shaking.

1. Type of motion: Compressional, like an accordion being squeezed and stretched. The ground particles move back and forth, parallel to the direction the wave travels.
2. Speed: The fastest seismic waves.
3. Travel through: Solids, liquids, and gases.
4. Effect: Create a push-pull motion on the ground.

S-waves (Secondary Waves)

S-waves, also known as secondary or shear waves, travel more slowly and shake the ground perpendicularly to the direction of propagation.

1. Type of motion: Shear or transverse, like shaking a rope up and down. The ground particles move perpendicular to the direction the wave travels.
2. Speed: Slower than P-waves.
3. Travel through: Only solids.
4. Effect: Create a shaking, side-to-side, or rolling motion of the ground.

	P-waves	S-waves
Speed	1.5–8 kilometers per second in the Earth's crust	60–70% of the speed of P-waves
Motion	Similar to a slinky	Similar to shaking a rope
Arrival	First to arrive at a seismograph	Second to arrive at a seismograph
Mediums	Can travel through solid, liquid, or gas	Can only travel through solids
Shaking	Shakes the ground in the direction of propagation	Shakes the ground perpendicularly to the direction of propagation
Destruction	Less destructive than S-waves	More destructive than P-waves

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