What is a Tide?
Tides are among the most predictable natural events on Earth. Just as the sun consistently rises in the east and stars illuminate the night sky, we can rely on the regular rise and fall of ocean waters along our shores.
Tides are essentially long-period waves that travel through the ocean, driven by the gravitational forces of the moon and the sun. These tides originate in the deep ocean and move toward the coastlines, where they manifest as the regular rising and falling of the sea level.
High tide occurs when the crest, or highest point, of the wave reaches a specific location. Conversely, low tide happens when the wave’s trough, or lowest point, arrives. The difference in height between high and low tides is known as the tidal range.
What is High Tide?
High tide occurs when the crest of a wave reaches a specific point on the shore, causing the ocean to rise to its highest level on the beach. This event typically happens twice a day on most coastlines and is influenced by the gravitational pull of the moon, and to a lesser extent, the sun, on Earth’s waters. The moon’s gravitational force is stronger on the side of the Earth closest to it, causing water to bulge toward the moon. Conversely, on the opposite side of the Earth, tides also bulge away from the moon.
During high tide, you might notice less sand available for walking and waves breaking closer to the shore or even at the top of the beach. The water is deeper, which can result in larger, more powerful waves.
It’s crucial to be mindful of tide times and heights for safety, especially if you plan to enter the water. As the tide rises, the water may become significantly deeper than when you first went in.
when do High tides occur
High tides in the UK occur due to the gravitational pull of the moon and the sun, combined with the rotation of the Earth, which creates a predictable rise and fall in sea levels. The moon’s gravity causes the ocean to “bulge” towards it, creating a high tide, while a second high tide occurs on the opposite side of the Earth due to centrifugal forces.
Most coastal areas in the UK experience semi-diurnal tides, meaning there are two high tides and two low tides each day. The timing of high tides shifts roughly 50 minutes later each day because the moon takes around 24 hours and 50 minutes to return to the same position relative to a specific location on Earth.
Local factors, such as the shape of the coastline and ocean basins, influence the exact timing and height of tides. As a result, the UK’s coastal regions have widely published tide tables to help residents and visitors predict high tides, which are essential for activities such as coastal walks, boating, and beach safety.
What is Low Tide?
Low tide occurs when the trough, or lowest point, of a wave reaches a specific location on the shore, causing the ocean to recede to its lowest level. This happens twice a day on most coasts, in sync with the gravitational forces of the moon and sun. During low tide, the moon’s gravitational pull is weaker on that part of the Earth, allowing the water to retreat from the shore.
When low tide occurs, more of the beach is exposed, revealing sand, tidal pools, and sometimes rocks or seaweed that are usually submerged. The water is shallower, and waves break further from the shore, often resulting in gentler wave activity.
Understanding low tide is important for various coastal activities, as the exposed shoreline provides opportunities for exploring marine life, but it can also make certain areas less suitable for swimming or boating due to the shallower water.
when do low tides occur
Low tides in the UK occur in the areas between the gravitational bulges of water caused by the moon and the Earth’s centrifugal forces. As water is pulled towards the high tide zones, the sea level drops in the areas perpendicular to them, creating low tides.
These typically happen twice daily in coastal areas experiencing semi-diurnal tides. Local geography, such as the shape of the coastline and the seabed, can influence the exact timing and depth of low tides, making tide tables essential for activities like rock pooling, coastal walks and sometimes beach days.
Whats the time between Low Tide and High Tide?
The time between high and low tide can vary, but on average it’s about 6 hours and 12.5 minutes. This interval is part of a semi-diurnal tidal cycle, the most common type of tidal pattern. In this cycle, a point on the shore experiences two high tides and two low tides within a 24-hour period.
Several factors can influence the time between high and low tides
Geography
The geographical features of a location can impact the timing between tides.
Gravitational forces
The gravitational pull of the moon and sun plays a significant role in determining the interval between tides.
Lunar day
The lunar day is slightly longer than a solar day, causing tide times to shift forward by about 50 minutes each day.
For accurate tide times, you can consult local tide charts. Checking the daily tide times and heights is also important for safety, especially if you plan to be near or in the water.
What causes high tide and low tide?
Tides are primarily controlled by the gravitational forces exerted by the moon and, to a lesser extent, the sun, as well as by the Earth’s rotation and inertia. These forces create the regular rise and fall of sea levels along coastlines, known as tides.
The Moon’s Influence
The moon’s gravitational pull is the dominant force controlling tides. As the Earth rotates, the moon’s gravity causes the oceans to bulge on the side of the Earth closest to it, as well as on the opposite side due to inertia. These bulges represent high tides. The areas between the bulges experience low tides, where the ocean is less elevated. As the Earth spins, different regions pass through these bulges, leading to the cyclical pattern of rising and falling tides.
The Lunar Day
A lunar day—the time it takes for a specific point on Earth to return to the same position relative to the moon—is about 24 hours and 50 minutes. This extra 50 minutes, compared to a solar day, is due to the moon’s simultaneous orbit around the Earth in the same direction as the Earth’s rotation. This results in the tidal cycle shifting slightly later each day.
The Sun’s Role
While the sun also exerts gravitational forces on Earth’s oceans, its influence on tides is about half as strong as the moon’s. The sun’s gravitational pull modifies the moon’s tidal patterns, leading to variations known as spring and neap tides, depending on the relative positions of the sun, moon, and Earth.
Inertia and Rotation
Inertia, the resistance of the ocean water to changes in motion, also plays a key role in the formation of tides. The tidal bulge on the side of the Earth opposite the moon is primarily due to inertia. As the Earth rotates, the interaction of gravity and inertia causes the tidal bulges to move around the planet, creating the alternating high and low tides.
Monitoring and Prediction
Scientists use advanced tidal recording systems and satellite imagery to monitor tides and water levels. This data is crucial for predicting ocean behavior, which helps protect coastlines and coastal communities from potential hazards.
Are there different types of tides?
Yes, there are different types of tides, and they vary depending on the location along Earth’s shorelines and the specific gravitational interactions between the Earth, moon, and sun. The main tidal patterns and special types of tides such as
- Spring Tides
- Neap Tides
- Semidiurnal Tides
- Mixed Tides
- Diurnal Tides
Whats the difference between high and low tide?
High tide and low tide are part of the regular tidal cycle caused by the gravitational pull of the moon and, to a lesser extent, the sun on Earth’s oceans. During high tide, the water level reaches its peak, causing the shoreline to recede as the ocean encroaches further onto land. This occurs when the area of the ocean is directly in line with the moon or on the opposite side of the Earth, where the moon’s gravitational pull creates a bulge in the water. High tides generally occur twice a day in coastal areas, with varying intensities depending on the location and the moon’s position in its orbit.
Low tide is when the water level is at its lowest, revealing more of the shoreline and shallow sea beds. Low tides occur in between high tides as the Earth’s rotation causes different parts of the ocean to fall under less direct gravitational influence from the moon. Like high tides, low tides also occur twice a day, creating a rhythmic rise and fall of the ocean. The difference in water levels between high and low tide, called the tidal range, can vary significantly based on geographical features like coastlines, bays, and estuaries.
What is a spring tide?
A spring tide is a type of tide that is higher than average and occurs when the gravitational forces of the moon and sun align, intensifying their combined pull on Earth’s oceans. This alignment happens during the new moon and full moon phases, roughly twice a month.
During a spring tide, both the high tides are higher than usual, and the low tides are lower than usual, leading to a larger difference between the two, known as a greater tidal range. Despite the name, “spring tide” has nothing to do with the season of spring; it derives from the concept of the tide “springing forth.”
Spring tides are most noticeable in coastal areas, where they can cause unusually strong tidal currents and, in some cases, contribute to coastal flooding or other tidal phenomena.
What causes spring tides?
Spring tides are caused by the alignment of the Earth, moon, and sun during the new moon and full moon phases. When these celestial bodies align, their combined gravitational forces create a stronger pull on Earth’s oceans, leading to higher high tides and lower low tides. This results in a greater difference between the high and low tides, known as a larger tidal range. The increased gravitational pull during these alignments is what makes spring tides more pronounced compared to regular tides.
What is a Neap Tide?
A neap tide is a type of tide that occurs when the gravitational forces of the moon and sun are at right angles relative to the Earth, which happens during the first and last quarter moon phases. During a neap tide, the pull of the moon and the pull of the sun partially cancel each other out, leading to weaker tidal forces. As a result, the difference between high and low tides is smaller than usual, producing tides that are lower than average high tides and higher than average low tides. This results in a smaller tidal range compared to spring tides.
What causes neap tides?
Neap tides are caused by the position of the moon and sun relative to the Earth, specifically when these celestial bodies form a right angle with the Earth. This alignment occurs during the first and last quarter phases of the moon.
When the moon and sun are at right angles, their gravitational forces partially counteract each other. The sun’s pull on the Earth’s oceans slightly diminishes the effect of the moon’s gravitational pull, leading to a reduction in the tidal range. As a result, during neap tides, the high tides are lower and the low tides are higher than average, producing less extreme tidal conditions compared to spring tides.
What is an Semidiurnal Tides?
Semidiurnal tides are a tidal pattern in which there are two high tides and two low tides of roughly equal height within a 24-hour period. This means that a location experiencing semidiurnal tides will go through a full cycle of rising and falling water levels twice each day. This type of tidal pattern is the most common globally and is typically observed along coastlines such as the eastern coast of North America. The regularity and predictability of semidiurnal tides make them a key feature in understanding coastal water movements.
What causes Semidiurnal Tides?
Semidiurnal tides are caused by the gravitational forces of the moon and sun acting on Earth’s oceans, combined with the rotation of the Earth. The moon’s gravitational pull creates two tidal bulges on opposite sides of the Earth—one on the side facing the moon and another on the opposite side due to inertia. As the Earth rotates through these bulges, most coastal areas experience two high tides and two low tides of similar height each day.
This regular pattern occurs because the Earth’s rotation brings each location under both tidal bulges within a 24-hour period. The relatively equal heights of the two high tides and two low tides in semidiurnal patterns result from the balanced gravitational effects of the moon and the Earth’s rotation.
What is a Mixed Tides?
Mixed tides are a tidal pattern characterized by two high tides and two low tides each day, but with a significant difference in the height of successive high and low tides. In other words, one of the high tides is typically much higher than the other, and one of the low tides is much lower. This results in a more complex tidal pattern compared to semidiurnal or diurnal tides.
Mixed tides are common along coastlines where the interactions between the gravitational forces of the moon and sun, combined with the local geography and oceanic conditions, create varying tidal ranges. This pattern is frequently observed on the western coast of North America and in other regions with similar coastal dynamics.
What causes Mixed Tides?
Mixed tides are caused by a combination of factors, including the gravitational forces of the moon and sun, the Earth’s rotation, and the specific geographic and oceanographic conditions of a region. Unlike semidiurnal tides, where the high and low tides are of similar height, mixed tides occur when these forces interact in such a way that one high tide is significantly higher than the other, and one low tide is significantly lower.
The variation in tidal heights is often influenced by the angle of the moon’s orbit relative to the Earth’s equator, known as the lunar declination, as well as the shape of the coastline, the depth of the ocean floor, and other local factors. These elements combine to create a more irregular tidal pattern, resulting in two unequal high and low tides within a 24-hour period.
What is Diurnal Tides?
Diurnal tides are a tidal pattern characterized by just one high tide and one low tide each day. This means that within a 24-hour period, a location experiencing diurnal tides will have a single cycle of rising and falling water levels. This type of tidal pattern is less common than semidiurnal or mixed tides and typically occurs in specific regions, such as the Gulf of Mexico, parts of Southeast Asia, and certain areas of the Arctic Ocean. Diurnal tides result from the gravitational forces of the moon and sun combined with the Earth’s rotation, but local geographical factors often play a significant role in creating this single daily tidal cycle.
What causes Diurnal Tides?
Diurnal tides are caused by a combination of the Earth’s rotation, the gravitational pull of the moon and sun, and specific geographic and oceanographic conditions. Unlike semidiurnal or mixed tides, where there are two high and two low tides each day, diurnal tides occur when these forces align in such a way that only one high tide and one low tide are experienced within a 24-hour period.
The Earth’s rotation plays a key role in diurnal tides, particularly in regions where the moon’s gravitational influence is more consistently felt on one side of the Earth. Additionally, the shape of the coastline, the depth of the ocean, and the local sea floor topography can amplify or diminish the tidal effects, leading to a single tidal cycle each day. Regions like the Gulf of Mexico and certain areas of Southeast Asia often experience diurnal tides due to these specific local factors.
How big are the UK Tides?
The tidal range in the UK varies significantly, from as little as 0.5 meters to as much as 15 meters, depending on the location and time of year. For instance, the Bristol Channel boasts one of the largest tidal ranges in the world, with an average spring tidal range of 12.2 meters. As the channel narrows from west to east, the tidal range increases and can exceed 14 meters in some areas during spring tides. In Avonmouth, the tidal range is 12.2 meters, while in Lowestoft, it is much smaller, at just 1.9 meters.
Weather conditions, such as strong winds and abnormal atmospheric pressure, can also influence the tidal range. For example, strong onshore winds can push water toward the land, leading to higher than expected tides.
Does the UK have the biggest tides in the world?
The UK’s Bristol Channel has the third largest tidal range in the world, measuring 9.60 meters (31.5 feet). The Severn Estuary, also in the UK, has a tidal range of 12–14 meters, making it the second largest globally, surpassed only by the Bay of Fundy in Canada. The combination of the Severn Estuary’s significant tidal range and its coastal geometry creates the UK’s largest tidal bore.
The Bay of Fundy boasts the world’s largest tides due to its unique shape and a phenomenon known as resonance, or seiche. The bay’s funnel-like shape amplifies the tides, significantly increasing their intensity.
Where can i find tide times?
For detailed tide times and beach information in Cornwall, visit CornwallOne.co.uk/beaches.
This section of the website offers comprehensive tidal predictions and information for various beaches across Cornwall, including popular spots like Fistral Beach, Perranporth Beach, Polzeath Beach, St Ives Beaches, Sennen Cove, Porthcurno Beach, and many more. Each subpage provides specific details about the beach, helping you plan your visit according to the tide times and local conditions.
Do riptides happen on both low tide and high tide?
On the west coast of Cornwall and Devon, sandbars that generate rip currents are often situated around low tide. As a result, rip current activity tends to be much more pronounced at low tide compared to high tide.
How does the moon affect the tides?
The moon’s gravitational pull on Earth causes the oceans to bulge, resulting in tides:
Bulges
The moon’s gravitational force creates bulges in the ocean on the side closest to the moon and on the side farthest from it.
Rotation
As Earth rotates, different landmasses move through these bulges, leading to the rise and fall of tides. A high tide occurs when the crest of a wave reaches the coast, and a low tide occurs when the trough reaches the coast.
Distance
When the moon is closest to Earth (perigee), its gravitational pull is stronger, leading to larger tides. When the moon is farthest from Earth (apogee), its pull is weaker, resulting in smaller tides.
Alignment
When the Earth, moon, and sun align, their combined gravitational forces create spring tides, which produce extremely high and low tides. This alignment occurs twice a month, such as during a full moon when the Earth is positioned between the moon and the sun.
Earth’s Position
Tidal ranges increase when Earth is closest to the sun (perihelion), around January 2. Conversely, tidal ranges decrease when Earth is farthest from the sun (aphelion), around July 2.
Why does the Moon affect the tides?
The moon influences tides through its gravitational pull, which causes Earth’s oceans to bulge on the side closest to the moon and the side farthest away. These bulges result in high tides, while the lower points between them create low tides. As the Earth rotates, different landmasses pass through these bulges, leading to the regular rise and fall of tides.
Although the moon’s gravitational pull is much weaker than Earth’s, its effect on the oceans is significant and easily noticeable. However, the moon isn’t the only factor influencing tides. The gravitational forces of the Earth and sun also play a role, particularly during full or new moons. During these times, the sun and moon align, and their combined gravitational forces create spring tides, which feature a large range between high and low tides. Other factors, such as the alignment of the sun and moon, the shape of the coastline, and atmospheric pressure, can also affect tidal patterns.
Are low tides and high tides dangerous?
Both low tides and high tides can present dangers, but the risks associated with each differ based on specific conditions and activities.
Low tide dangers
As the water recedes, previously submerged hazards like sharp rocks, seaweed, or sandbars can become exposed. This can lead to injuries for swimmers, surfers, or those walking along the shore. Additionally, during low tide, people exploring tidal flats may venture too far out and risk becoming stranded when the tide quickly rises. Fast-moving tides in some areas can leave people cut off from the shore. Low tides can also create shallow waters, making it challenging for boats to navigate, increasing the risk of running aground.
High tide dangers
High tides can lead to coastal flooding, especially during storm surges, when the tide combines with strong winds and low-pressure weather systems. High tides can push water further inland, flooding roads, homes, and infrastructure in low-lying coastal areas. For swimmers and surfers, higher tides can bring stronger currents and waves, which can be hazardous. Rip currents, which are strong, narrow currents flowing away from shore, can become more intense during high tides, posing a risk of pulling swimmers out to sea. Always being mindful of tide schedules and local conditions is essential for safety in coastal areas.
Whats the biggest tides in the world?
The largest tides in the world occur in the Bay of Fundy, located between the Canadian provinces of Nova Scotia and New Brunswick. The tidal range here can reach up to 16 meters (about 53 feet) during the highest tides, which are known as spring tides. This extreme tidal range is due to the unique funnel shape of the bay, which amplifies the tidal movements. As the ocean water is pushed into the narrow, shallow bay, the tides rise dramatically compared to other areas.
Another location with large tides is the Severn Estuary between England and Wales, where tidal ranges can exceed 15 meters (about 50 feet). Similar to the Bay of Fundy, the shape and geography of the estuary contribute to its extreme tides. These locations are famous for their dramatic ebb and flow, with vast amounts of water moving in and out daily, creating strong tidal currents and influencing the local environment and wildlife.
