Tides



Published on 02 Feb 2025

Tides are the rising and falling of sea levels caused by the gravitational pull of the moon and the sun on Earth's oceans.

Mechanism of tides 

Tides form due to gravitational forces between Earth, the Moon, and the Sun. The Moon's proximity creates high tide bulges on opposite sides of Earth. The Sun's gravitational pull influences tide intensity. Earth's rotation and centrifugal force contribute to two daily high and low tides. 

Types of tides 

  • Based on frequency

  • Semi-diurnal tide: Two high tides and two low tides each day.

  • Diurnal tide: One high tide and one low tide each day. 

  • Mixed tide: Tides of different heights.

  • Based on the positions of the sun, moon and earth

  • Spring tide: High tide forms when the sun, moon and earth are in the same line and occurs twice a month during the full moon and new moon.Types of tides and their difference - Science Query

  • Neap tide: Occurs when the sun, moon and earth are at right angles. These are weaker tides occurring during the first and third quarters of the moon, with reduced tidal range. Gravitational forces offset.

  • Based on the distance between Earth and the moon

    • Perigean tides: High tides due to the proximity of the moon to Earth. It occurs once a month.

    • Apogean tides: Low tides due to the farthest distance of the moon to Earth. It occurs once a month.

  • Based on the distance between the sun and the earth

    • Perihelion tides: High tides due to the proximity of the sun to the earth.

    • Aphelion tides: Low tides due to the farthest distance of the moon to Earth.


Significance of tides

  • Navigation: High tide helps in harbours near rivers and in estuaries with shallow depths for the entry of ships.

    • Example: The tidal range in the Bay of Fundy, Canada, is significant, impacting ship navigation.

  • Renewable Energy: Tidal energy can be harnessed for power generation through tidal turbines.

    • Example: The Rance Tidal Power Station in France

  • Erosion and desiltation of sediments: Tidal action plays a role in coastal erosion and sedimentation, influencing the shape and structure of coastlines.

    • Example: Shifting sands along barrier islands such as the Outer Banks in the United States

  • Aquaculture: Tidal cycles are considered in aquaculture practices, influencing the growth and health of farmed marine organisms.

    • Example: Oyster farming often considers tidal patterns, as nutrient-rich tidal waters enhance growth.

Comparison- wave, tide and current

Factors 

Tides

Current

Waves 

Definition 

Periodic rise and fall of sea levels caused by the attraction exerted by the moon and the sun

Continuous, directed movement of seawater.

Oscillations of the water's surface caused primarily by the wind. They transfer energy across the water without a net displacement of water.

Cause 

Gravitational forces from the moon and the sun cause the water to move in and out, creating the rise and fall of tides.

Caused by wind, temperature differences (thermohaline circulation), and the Earth's rotation (Coriolis effect).

It is primarily caused by the wind. The friction between the wind and the water's surface transfers energy and creates wave motion.

Motion 

The rhythmic rise and fall of sea levels, occur at regular intervals.

Exhibit continuous, directional flow, transporting water over large distances.

Involve the periodic oscillation without significant net horizontal motion of water.

Frequency 

Regular, predictable frequency typically two high tides and two low tides in a 24-hour period.

It can be constant or variable, depending on the cause.

They can be short-period waves generated by local winds or long-period waves generated by distant storms.

Scale 

Tidal effects are global, affecting entire ocean basins.

Currents can be local, regional, or global in scale.

Scale is often influenced by the local wind conditions.


Tags:
Geography

Keywords:
Tides Mechanism of tides types of tide Significance of tides Comparison- wave tide and current

Syllabus:
General Studies Paper 1

Topics:
Physical Geography

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