American Oceans

What Are Tides? A Guide to High and Low Tide

The term “tide” refers to the periodic changing of sea levels as the result of gravitational pull exerted by celestial bodies, such as the moon.

They’re incredibly reliable phenomena, and this rise and fall of sea levels are usually regular and predictable.

The moment the sea reaches its maximum level on a certain coastal location is referred to as high tide, while the moment it reaches its minimum level is referred to as low tide.

Tides are categorized into three varieties based on the frequency and symmetry of their wavelength.

picture of sea floor during low tide

Semi-diurnal tides are the most common type, and it consists of 2 high tides and 2 low tides in one lunar day (approximately 25 hours). 

Diurnal tides consist of just 1 high tide and 1 low tide on each lunar day.

Mixed tides occur when 2 high tides and 2 low tides occur in one lunar day, but the range between the tides is usually dramatic. The difference in height between the high tide and the low tide is called the tidal range.

The vast majority of the earth will experience two tides per day or within a 24-hour period. There are two high tides and two low tides. A high tide and a low tide are usually separated by 6 hours and 12.5 minutes.

Many industries, including shipping, fishing, and coastal engineering, rely on tide knowledge, so they monitor and track tides. Tides can be hazardous as well. It is critical to understand whether the tide is coming in or going out.

How Do Tides Affect Life?

Boat on shore far from water because of low tide

Every natural occurrence is significant and has an impact on living things, and the tide is no exception. The following are some of the ways in which tides might affect life on Earth:

Fishing 

The feeding cycle of some fish is directly influenced by tide movements.

Most fish that cling to coastal locations eat mostly on flood tides, which occur when microscopic organisms are washed with warm water in winter and cold water in summer.

The tidal movement offers one of the three most important things that fish require: food.

Miniature marine animals and plants are dragged along by currents, concentrating them in small whirlpools where a structure, such as reefs or rocks, disturbs the flow of water.

Tidal Zone Foods

The tidal zone is home to edible marine species such as crabs, mussels, snails, seaweed, and so on.

It is crucial to remember that without the regular washing of the tides, these sophisticated and diverse creatures would die and food resources would decline.

Navigation

High tides can also be utilized for the purpose of navigation. They raise the water level near the coasts, making it easier for ships to enter the harbor. This is beneficial to life in terms of trade and travel.

All commercial vessels carry high and low tide guides to help them navigate. Knowing when high and low tides will occur is very important while sailing in a shallow river or anchoring at a port.

Weather

The tides can also affect the weather as they stir the ocean currents and create habitable conditions for marine life. The tides can also help to balance the temperature of the ocean as well as the planet, impacting all life on it.

Tidal Energy

Typically, two high tides and two low tides occur every 24 hours. As a result, the rapid movement of water during inflow and outflow will provide a sustainable energy source to those living along the coast.

The use of tidal energy is still in its infancy and will hopefully be used more in the future to help protect life on Earth.

How Do Tides Work?

A tide is the alternating advance and retreat of seawater along a shoreline. When the water reaches its greatest extent along the shoreline, it is said to be at high tide.

When the tide recedes to its greatest extent, it is said to be at low tide. Tides can occur in several freshwater rivers and lakes, as well as seas and oceans.

How Tide is Formed:

High and low tides are caused by the moon’s gravitational pull on the Earth and the Earth’s rotational force.

The side of the Earth nearest to the Moon will experience the strongest pull, causing oceans to rise and high tides to occur.

The rotating force of the Earth is greater than the gravitational force of the Moon on the side facing away from it. Because the rotational force causes water to build up as it tries to resist the force, high tides arise on this side as well.

The ocean recedes elsewhere on Earth, resulting in low tides.The Sun’s gravitational attraction also plays a minor influence in the production of tides. Tides circulate the Earth as bulges in the ocean.

Are Tides the Same Everywhere?

You’d think that as land goes beneath the bulge of water, the time of high water would be nearly the same for all places along the coast, but that’s not the case.

The land ‘gets in the way’ of the moving water, which causes this difficulty.

The water has to flow as the Earth spins to generate the high tides, but there is a lag due to the geometry of the coastlines and the variance in sea depth (bathymetry).

Every region has a distinct shoreline and bathymetry, which results in a distinct tidal pattern.

Are Tides Stronger During a Full Moon?

Yes, full moons are often associated with Spring tides. Spring tides occur just after every full and new moon, when the sun, moon, and earth align.

That is when the lunar and solar tides align and reinforce one another, resulting in a larger total tide. 

Neap tides occur when the moon is in its first or third quarter, forming a right angle between the sun, earth, and moon.

The lunar high tide coincides with the solar low tide, and they somewhat cancel each other out, resulting in a small overall tide.

Spring tides all differ in size. Springs are slightly larger near the equinoxes (March 21 and September 21 – when day and night are of equal length all over the world).

You’ll notice that tides are usually strongest during or after a supermoon, and this is simply because the moon is closest to Earth, and so the Earth’s oceans are feeling the greatest powerful pull of the moon’s gravity. 

However, these peak tides are unlikely to occur on the exact day of a supermoon. The highest tides usually occur a day or two after the supermoon (or any new or full moon).

Also, it’s important to remember that the most extreme high tides don’t always necessarily occur during supermoons. 

It’s when a spring tide coincides with a time of heavy winds and rain, flooding due to a weather extreme, that the most extreme flooding occurs.

Does the Sun Affect Tides?

The Moon has the greatest influence on measurable tides, although the Sun also has some influence on tides. Spring and neap tides occur when the Sun, Moon, and Earth are in a specific constellation.

Spring tides are tides that have an unusually high tide and an unusually low water level. 

Neap Tides occur at half Moon when the Sun, Earth, and Moon form a 90-degree angle.

Under these conditions, the gravitational bulges of the Moon and Sun overlap destructively because the Sun’s tidal forces act against the Moon’s tidal forces. 

The difference between high and low tide is the smallest at neap tide. Neap tides happen approximately twice a month, once around the first quarter moon and once around the last quarter moon.

Tides can be predicted with a great degree of precision and far in advance. Tides are caused by the Earth’s, Moon’s, and Sun’s orbital interactions.

These correlations are well understood, and the positions of the stars and planets may be predicted extremely precisely in the future.

Ultimately, the height of the tides is affected by the sun, the moon, the shape of a beach and the size of the coastline, the angle of a seafloor going up to land, and the prevailing ocean currents and winds.

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