Bengal issues high tide warning for coastal areas

Bengal issues high tide warning for coastal areas

Subject : Geography

Context : The West Bengal government issued an alert in the coastal areas and evacuated a few thousand people from islands exposed to the Bay of Bengal over fears of fresh inundation due to a high tide on Friday.

Concept :

• The Periodic rise and fall of the sea level due to the gravitational pull of the Moon and Sun, once or twice a day, is called tides.
• Ocean Tides are one type of wave characterized by rhythmic rise and fall of ocean water twice a day.
• Tides make ocean water move vertically.
• The study of tides is complex, spatially, and temporally; as it has great variation in frequency, magnitudes, and height.

Cause of tides

• The gravitational pull of the Moon.[ Strong factor]
• Gravitation pull of Sun. [ Less factor]
• Centrifugal force, the force that works as a counterbalance of gravity.
• Gravitation pull and centrifugal force are responsible for the creation of two major tides on earth.
• On the moonward side of the earth, tidal bulge is caused by the gravitational pull from the Moon, and the opposite side of the earth’s bulge caused by centrifugal force.
• Highest tides experienced on Bay of Fundy in Canada; it is approx 15-16 m high.

Types of tides:

Based on the frequency of tide, the following are the types of tides:

• Semi-diurnal tide: Two high and two low tides with the same height on each day.
• Diurnal tides: Only one high tide and one low tide with the same height each day.
• Mixed Tides: Tides having variation in height is called mixed tide.

Types of tides based n the Sun, Moon, and earth Position:

• Spring Tides : During full moon and new moon days. The sun, moon, and earth are the same line and tides are highest.
• Neap Tides : When the moon is the first and last quarter, ocean water gets diagonally opposite direction resulting in low tides. These are called neap tides.

The factors affecting the height of the tides:

• When the Moon is closed to earth at Perigee position; experiences higher tides or greater than the normal tides.
• When the Moon is the farthest from the earth at apogee position; experiences less than average tides bulge.
• When the Earth is closed to Sun at Perihelian position; experiences higher tides or greater than the normal tides.
• When the Earth is the farthest from the Sun at the aphelian position; experiences less than average tides bulge.
• Ebb: It is the time between the high tide and low tides when water is falling.
• Flood or flow : It is the time between the low tide and high tides when water is rising.