Context:
The Indian National Centre for Ocean Information Services (INCOIS) had forecasted Swell waves likely to hit several coastal areas in India over the weekend.
Swell Waves:
- Series of Ocean surface waves that propagate along the interface between water and air
- Referred to as – Surface gravity waves.
- Formed by an ocean swell, hence the name swell surge.
- Formation –
- Swells (series of waves) are generated over the open ocean by distant storms like hurricanes, or even long periods of fierce gale winds and not by any local wind.
- During such storms, huge energy transfer takes place from the air into the water, leading to the formation of very high waves.
- Mainly originate in – Antarctica, where there is high winds with nearly infinite duration
- Kallakkadal – Refers to coastal flooding caused by swell waves during the pre-monsoon season
Difference between Wind Waves and Swell Waves:
| Wind waves | Smell waves |
| Generated by local wind. | Generated by distant storms. |
| Tend to be irregular. | Regular series of waves. |
| Not self-sustaining and will die out when the wind stops. | Self-sustaining. |
| Relatively lesser speed and cover lesser distances. | Larger wavelength and period. |
Difference with Tsunami:
- Tsunami – Series of enormous waves created by an underwater disturbance, usually associated with earthquakes occurring below or near the ocean.
- Swell waves (like Kallakkadal) have a wavelength of only 30 or 40 meters, tsunamis have a very long wavelength often hundreds of kilometers long.
Source: The Indian Express
Previous Year Question
The 2004 Tsunami made people realise that mangroves can serve as a reliable safety hedge against coastal calamities. How do mangroves function as a safety hedge?
[UPSC Civil Service Exam – 2011 Prelims]
(a) The mangrove swamps separate the human settlements from the sea by a wide zone in which people neither live nor venture out.
(b) The mangroves provide both food and medicines which people are in need of after any natural disaster.
(c) The mangrove trees are tall with dense canopies and serve as an excellent shelter during a cyclone or Tsunami.
(d) The mangrove trees do not get uprooted by storms and tides because of their extensive roots
Answer: (d)
