13.2.2. Types of Tides

Tides vary in their frequency, direction, and movement from place to place and also from time to time.

Tides are not uniform; they can change depending on geographical locations and time. This means that in one place, tides may come in and out more frequently than in another.

Think of how a busy highway has varying traffic patterns at different times of the day. During rush hour, many cars (or tides) enter and exit quickly, whereas at night, flow is slower and less frequent.

Tides may be grouped into various types based on their frequency of occurrence in one day or 24 hours.

The classification of tides based on how often they occur in a day helps us understand the patterns of sea level changes. There are three main types: semi-diurnal, diurnal, and mixed tides.

It's similar to how in a school, classes can be scheduled at different intervals. Some subjects might have classes every day (semi-diurnal), while others may have classes once a week (diurnal), and some might be scheduled irregularly (mixed).

Semi-diurnal tide: The most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are approximately of the same height.

In a semi-diurnal tide, you can expect to see two high tides and two low tides each day, and these tides generally have similar heights.

Think of it like the sun rising and setting twice a day; each event is predictable and relatively consistent in timing and intensity.

Diurnal tide: There is only one high tide and one low tide during each day. The successive high and low tides are approximately of the same height.

With a diurnal tide, the ocean experiences one high tide and one low tide each day, and these tides also tend to be of similar heights.

Imagine a single classroom where students arrive for one assembly (high tide) and leave after it ends (low tide) once a day, making it very straightforward and predictable.

Mixed tide: Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean.

Mixed tides are characterized by variations in height, meaning that the high and low tides can differ significantly from one another in their measurements.

Think of a seesaw: sometimes one side goes much higher than the other, just like how mixed tides can show large differences in the heights of high and low tides.

The height of rising water (high tide) varies appreciably depending upon the position of sun and moon with respect to the earth.

The gravitational forces exerted by the sun and moon affect the height of tides. This means that when these celestial bodies align in certain ways, the tides can be significantly higher or lower.

Similar to how the pull of our hands can affect a balloon's movement when we push or pull on it—here, the sun and moon influence the tides based on their positions.

Spring tides: When the sun, the moon, and the earth are in a straight line, the height of the tide will be higher. These are called spring tides and they occur twice a month.

Spring tides occur when the sun and moon are aligned with the Earth, resulting in higher-than-normal tides. These happen during full moons and new moons.

Think of how pulling on a rope with more people can lift a load more easily—when the gravitational forces of the sun and moon align, they lift the ocean water higher.

Neap tides: At this time the sun and moon are at right angles to each other and the forces of the sun and moon tend to counteract one another.

Neap tides occur when the sun and moon are perpendicular to each other, leading to lower tides since their gravitational forces counteract.

Imagine trying to lift a heavy box alone while a friend pushes down on the other side—the result will be a lower height—this is what happens with neap tides.

The time between high tide and low tide, when the water level is falling, is called the ebb. The time between low tide and high tide, when the tide is rising, is called the flow or flood.

Understanding these terms helps in recognizing the dynamics of water movement. Knowing when the tide is ebbing or flowing can inform activities like fishing, boating, or beachcombing.

It's like knowing the rhythm of a breathing exercise; when to inhale (flood) and when to exhale (ebb) helps you manage your practice effectively.

Since tides are caused by the earth-moon-sun positions which are known accurately, the tides can be predicted well in advance.

Predicting tides is essential for navigation and fishing. Knowing the tide schedule allows fishermen to plan their trips and navigators to ensure safe passage.

Just like a train schedule helps passengers know when to arrive at the station, knowing tide patterns ensures that sea voyages are safe and productive.

--