Ocean Tides, Causes, Classification, Significance & Diagram

Ocean Tides

Ocean Tides: Seawater is not stationary but rises and falls twice a day at constant intervals. This periodical rise and fall of the sea level, once or twice a day is called a tide. Twice a day about every 12 hours and 26 minutes, the sea level goes up and down. The rise is called the flood tide, and the fall is the ebb tide. This happens mainly because of the gravity of the Earth, the sun, and the moon, along with the Earth’s rotation. Changes in water caused by weather, like wind and pressure changes, are called surges. Surges are not regular like tides.

Ocean Tides Causes

• The Moon’s gravitational pull.
• The Sun’s gravitational pull.
• The force that acts as a counterbalance to gravity is known as centrifugal force.
• The two major tides on Earth are caused by gravitational pull and centrifugal force.
• The gravitational pull of the Moon causes a tidal bulge on the moonward side of the earth, and centrifugal force causes a bulge on the opposite side of the earth.
• The highest tides in Canada have been observed on the Bay of Fundy; they are approximately 15-16 m high.

Ocean Tides Formation

• Tides are caused by the gravitational pulls of the Sun and Moon.
• The Moon’s pull has a stronger effect on tides than the Sun’s.
• The centrifugal force which acts in the opposite direction to gravity also influences tides.
• The ocean bulges toward the Moon, creating high tides, while the opposite side experiences a second bulge due to centrifugal force.
• Low tides (troughs) occur halfway between the two high tide bulges.
• Tidal bores happen when rivers meet the ocean, creating a wave if the incoming tide is stronger than the river flow.

Ocean Tides Classification

Tides are classified based on the frequency of occurrence and the height of the rising water (influenced by the position of the earth, the sun, and the moon).

Classification Based on the Frequency

1. Semi-diurnal Tide

The semi-diurnal tidal pattern features two high tides and two low tides every day. The height of the successive high and low tides is approximately the same. This is the most typical type of tide. They have a period of 12 hours and 25 minutes and a wavelength of more than half the circumference of Earth. It is also the type of tidal cycle one could expect from a planet covered entirely with water and without any continents obstructing the free movement of water.

2. Diurnal Tides

A diurnal tidal cycle is a cycle with only one high and low tide each day. The Gulf of Mexico and the East coast of the Kamchatka Peninsula have diurnal tidal cycles.

3. Mixed Tides

A mixed tidal cycle is a cycle with two high and low tides of different sizes each lunar day. The difference in height between successive high (or low) tides is called diurnal inequality. Areas with a mixed tidal cycle can be found alongside the West coast of the USA, in parts of Australia, and in South East Asia.

Classification Based on the Height of the Tides

The high tide fluctuates significantly based on the sun’s and moon’s positions in relation to the earth. This results in two types of tides: the spring and the neap tides.

1. Spring Tides

We know that tidal height is directly related to the location of the sun and moon with respect to the earth. The tide will be higher when the sun, moon, and earth are all in a straight line. Spring tides occur twice a month, once at the full moon and once at the new moon.

2. Neap Tides

The solar tidal force partially cancels the Moon’s gravitational force.  Although the Moon’s attraction is more than twice as strong as the sun’s, it is weakened by the sun’s gravitational pull. These tides occur at certain times in the lunar cycle when the range of the tide is at its smallest. The spring and neap tides are separated by seven days in most cases.

These tides occur twice a month, just like spring tides.

Ocean Tides Significance

Tides may seem relatively isolated geographical phenomena concerning their direct impact on the lives of humans. However, this is not true tides play an essential function in our day-to-day activities.

1. Ship Navigation

Tides are very important for ship navigation. They help make some rivers accessible for ocean ships and allow easier entry to harbors. Strong tides are especially helpful in shallow areas, making it possible to navigate channels that would be difficult otherwise. For example, ships rely on tides to reach the ports of London and Kolkata.

2. Fishing

High tides are a fisherman’s dream. During high tide, the fish get closer to the coast, and this helps the fishers with a better catch.

3. Desilting

When rivers meet the ocean, they drop a lot of silt at their mouths. This silt can block the flow of water. The movement of tides helps clear out this silt and remove dirty water from river estuaries.

4. Generation of Electricity

Tides are a mechanical movement of water that can be used to generate electricity. Tidal energy is a good non-renewable energy source. This has been successfully used in Canada, France, Russia, and China. In India, a 3 MW tidal power project was built in the Sunderbans of West Bengal’s Durgaduani.

Ocean Tides UPSC

Tides make ocean water move vertically. Tides are the periodic rise and fall of the sea level caused by the gravitational pull of the Moon and Sun, which occurs once or twice a day. Ocean tidal waves are characterised by the rhythmic rise and fall of ocean water twice a day. A solid understanding of this subject is required to help individuals pass competitive exams. On that note, we have covered this topic exclusively for students preparing for the UPSC and IAS exams.

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