MERSEYSIDE has one of most populated coastlines of the UK and its industry, tourism and environment can be heavily effected by the tidal patterns that happen each day. Therefore, tides play an important part in our community, but why do they happen and what are they? This section is all about tides, looking at how and why they happen, as well as it's effects and what Liverpool did about it.
The knowledge about how tides are caused was explained first by an English physicist and mathematician called Sir Isaac Newton (1642 -1727). He was the first person to explain tides scientifically, within a paper published in 1686, in the second volume of the Principia.
The word "tides" is a generic term used to define the alternating rise and fall in sea level with respect to the land. Tides we now understand as a combination of gravitational effects that are caused by the forces exerted by the Moon and the Sun and the rotation of the Earth. This means that mostly the coastlines throughout the world experience 2 tides a day, but in addition local geographical factors can result in extra tides, like on the UK Coastline, Southampton has 4 tides. The extra tides in Southampton are the result of the effects of the gravitational pull of both the Sun and the Moon on the North Sea and also their effects on the Atlantic, both pushing and pulling the water within the English Channel. This creates a 'Double High Water'. The Irish Sea on the Merseyside Coastline is not affected by that type of phenomena, so it only has the normal High and Low Water changes along its coastline, meaning just 2 tides a day. This daily fluctuation in water height along the Merseyside coastline daily results in many interesting effects on the environment around us, from social and business, to our landscape. Most importantly for Merseyside, early response to the effects of tides from the Irish Sea enabled Liverpool to adapt and to use tides to build its fortunes before others could follow. Without tides this could have been very different story. Knowing why tides happen and also their effects on us might look like an unimportant part of life, but in reality it plays a major part of our day to day life, from safety to the economy. This daily rhythm is played out over the whole maritime world and affects everything from building projects to the transportation of goods though shipping.
The tides alternating heights of waterleaves along the Merseyside coastline daily results in many interesting effects on the environment around us, from social and business, to our landscape. Most importantly for Merseyside, the effects of tides on the Irish Sea have enabled Liverpool to develop and use tides to build its fortunes. Without tides this could have been very different story. Knowing why tides happen and also its effects on us might look like an unimportant part of life, but in reality it plays a major part of our day to day life, from safety to the economy. In most parts for Merseyside and the UK as a whole, this daily rhythm that is played out all over the world affects everything from building projects to the transportation of goods though shipping.
Did you know that tides can even affect the weather around us? Tides also produce oscillating currents known as tidal streams that affect our climate and more.
Thankfully, for the most part tide times and heights can be predicted easily. If we didn't know the times, heights, and extent of the tides, we would not be able to safely navigate commercial and recreational watercraft through coastal waterways and estuaries, or build property along our shorelines. Today’s planners and builders need to remember these facts to challenge without great care is foolish. Knowledge about the tides also allows us to create data that is useful to many commercial, water-sports and tourism activities such as fishing, surfing, and paddling on the beach safely. The military, commercial and some recreational activities can also use these predictions to aid in things like underwater exploration and construction.
As we have just mentioned Tides are mostly caused by the forces exerted by the Moon and the Sun's gravitation on our planet’s bodies of water, but other factors play their parts. Some environments and geological effects can also alter slightly the predicted height, as can weather. Gale force winds may 'hold back' a tide for a period of time, or 'push' a tide higher, as seen very dramatically in recent storms. But for the most part, the biggest effect is the gravitational pull of the 2 most important heavenly bodies above us.
Centrifugal force, a result of the Earth spinning around in space, also plays a considerable part in determining tides. When a body of water is furthest away from the effects of the Sun and the Moon, the attraction of external gravitational forces is less. As the Earth spins the water picks up momentum and wants to keep going off in a straight line. Think of a rock in a sling. The object is swinging around and round and then when the sling stops it shoots out at speed. Luckily for us Earth's gravity is holding it "down". So, when not being pulled by the Moon or Sun, this centrifugal force acting on body of water can lag behind a bit until it is pulled again. The first bulge is a combination of the spin of the Earth and the added gravitational pull of the Moon, creates a stronger tide as the bulge water accelerates toward the Moon. The Sun also produces tides but the effects are much less significant. However, when the Moon, Earth and Sun are aligned, the combined gravitational pull of the 2 bodies causes our highest tidal changes, known as Spring Tides. Spring Tides happen when both the Sun and Moon are on the same side of the Earth (New Moon) or when the Sun and Moon are on opposite sides of the Earth (Full Moon). Equally the weakest tides are known as Neap Tides, and happen when the Moon is in its First Quarter or Last Quarter phase (meaning that it is located at right angles to the Earth and Sun line).
The Seashore has several states throughout the day. As the water levels rise and fall, the effect is that the coastlines seabed can be exposed at low tide and hidden by water at high tide. This effect is known as Tide Range. The topography of an area, such as the gradient of the beach and factors which concentrate flow, helps determine the speed and depth of the incoming and outgoing water This is why it is important for you to check the tide times before you head to the beach or go to sea as appearances can be deceptive and dangerous, none less than the treacherous currents around Sefton’s coast. This daily change in sea level is not only an important ecological one, but also extremely important for anyone on that uses our shorelines. Liverpool experiences a wide range of tidal heights(up to 32ft) and it was this fact that galvanised this city to lead the world, by developing the World’s very first, fully functioning Wet Dock, completed in 1715, which allowed as much as 10% of the water out between high tides, resulting in a water level drop of several feet.
The first docks allowed as many as 100 ships to birth safely, and unload and load no matter what the height of the tide was out in the river Mersey's Estuary. These developments lead the City on the path that transformed Liverpool into one of Britain's foremost cities. Liverpool became a financial centre, only beaten only by London. Sadly, many years on, that first commercial advantage might have been long lost, but Liverpool had not only secured its place in the history books, but it had kick-started Liverpool's development as a major port which is still in operation today. The original dock can still be found situated under Liverpool One and you can take a look at Liverpool's revolutionary structure today. If you want to find out more about the history of the Merseyside and Lancashire coastline, please visit our history section for more about the docks and other interesting historical facts.
Just to reiterate. Please remember that it is extremely important that should you ever visit the seaside and go for a walk or swim, you should always check the tide times. The tides do come in twice a day, even in Southport. The coastline around Merseyside is some of the most dangerous in the UK, so please enjoy our coast, but stay safe and always read the information signs and check the tide times!
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See our Lunar page to find out more about the moon.
Find out about developments along the Merseyside Coastline that have been affected by the tide on our History Pages by clicking on here.
Liverpool Museum - The World Museum (Liverpool) houses a range of extensive collections covering subjects from archaeology, ethnology, natural and physical sciences. Special attractions at the museum include the Natural History Centre and a Planetarium.