Ocean Waves & Movements of Ocean Water –Geography UPSC Notes

GS-I
Geography
10 Sep,2023

Ocean Waves are oscillatory surface water movements that result in the rise & fall of surface water.

Ocean Waves: An Ocean wave is a ridge or a swell on the surface of a body of water. They are oscillatory surface water movements resulting in the rise and fall of surface water. Waves are the horizontal movements of ocean water. They are the energy that moves across the ocean surface, not the water itself. The wind provides this energy for the waves. Each water particle in a wave moves in a circular motion. The raised portion of a wave is known as the crest, while the low point is known as the trough.

Motion of Ocean water can be classified in two directions –

HORIZONTAL
VERTICAL

Horizontal movements of the ocean waters can be classified into two –

WAVES
CURRENTS

Vertical movements of the ocean waters can be classified into two –

TIDES
UPWELLING

Waves are nothing but oscillatory movements that result in the rise and fall of the water surface.

Waves are a kind of horizontal movement of ocean water.
They are actually the energy, not the water as such, which moves across the ocean surface.
This energy for the waves is provided by the wind.
In a wave, the movement of each water particle is in a circular manner.
A wave has two major parts: the raised part is called the crest while the low-point is called the trough.

Parts of a wave

Wave crest and trough	The highest point of a wave is called a crest. The lowest point of a wave is called the trough.
Wave height	It is the perpendicular distance from the bottom of a trough to the top of a crest of a wave.
Wave amplitude	It is one-half of the wave height.
Wave period	It is merely the time interval between two successive wave crests or troughs as they pass a fixed point.
Wavelength	It is the horizontal distance between two successive crests.
Wave speed	It is the rate at which the wave moves through the water. It is measured in knots.
Frequency	the number of complete waves (or oscillations) that occur over a given period of time. Usually measured in cycles per second.

Most of the waves present on the ocean’s surface are wind-generated waves.

Friction from the wind moving over the water causes the water to move along with the wind. If the wind speed is high enough, the water begins to pile up and a wave is formed.
As wind velocity increases: Wavelength, Wave period, and Height Increase.

Water molecules move in an orbital motion as the wave passes.

Particles of water move around in circles. The farther below the surface, the smaller the circle.

The diameter of the orbit: increases with increasing wave size.
The diameter of the orbit: decreases with depth below the water surface.

As the wave slows, its crest and trough come closer together. The top of the wave is not slowed by friction and moves faster than the bottom.

Waves

Waves are formed by energy passing through water, resulting it to move in a circular motion.
Water particles travel only in a small circle as a wave passes.
The Wind provides energy to the waves.
The Wind causes waves to travel in the ocean and the energy is released on coastlines.
The movement of the surface water rarely affects the stagnant deep bottom water of the oceans.
As a wave approaches the coastline, it slows down. This is due to the friction happening between the moving water and the seafloor.
When the depth of water is less than half the wavelength of the wave, the wave breaks.
The largest waves are found in the open oceans.
Waves continue to grow larger as they move and absorb energy from the wind.
The size and shape of the waves reveal its origin.
Steep waves are young ones and are perhaps created by local wind.
Slow and steady waves originate from faraway places, probably from another hemisphere.

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