Many tourists vacationing at resorts in Thailand and Vietnam, faced with such natural phenomena as the ebb and flow of the sea.At a certain hour of the water suddenly recede from the usual edge, exposing the bottom.It pleases the locals: the women and children go to the bank to collect not had time to evacuate, along with casting wave crustaceans and crabs.And at another time the sea starts to attack, and after about six hours of standing aloof beach chair is in the water.Why is this happening?What is the reason for this?Why, for example, in the Black or Azov seas, we do not observe the tides, and near Murmansk daily fluctuations in water level are significant?Let's look at these mysteries of the ocean.
Physics natural phenomenon
Paradoxically, as the cause of the tides on the Earth is its satellite.It would seem that common in the bottomless depths of the seas with a celestial body?The fact that not only the earth keeps the moon in orbit its attraction.This process is common.Luna also has a weight (and small), and therefore the force of gravity acting on the planet.Month Stones does not raise, but such an easy matter, as water can.World Ocean as bends toward the moon.And because the satellite of the Earth moves in its orbit (for us - on the horizon), and the high water moves him.The quiet in the open ocean, wave manifests itself off the coast, in the narrow bays and in shallow water, causing the tide.The sun also influences the force of attraction of huge masses of water.It shone a lot more weight than that of the Month, but it is four hundred times farther from Earth than our moon.And because solar tides twice weaker than the moon.
Frequency tide
Logically, the highest water level should be observed at the time when the moon is at its zenith.When the month is at the nadir, we can expect lower, leaving a wave.But the strange thing: the ebb and flow are observed twice a day.And the second time is when the moon is at the nadir (the point opposite the zenith).This is because the satellite still attracts water, even through the entire thickness of the globe.Thus, the level of the World Ocean can be likened to an ellipse, elongated ends of which lie on the same axis with the Moon, and flattened perpendicular to it.Besides it is not necessary to dismiss such an important factor, as a proper rotation of the Earth on its axis.Huge masses of water under the influence of centripetal force wave form two mutually opposite points of the globe.
Why is the power of this phenomenon is not uniform in the different points of the Earth
In theory, in all the coasts, we must observe the same forces of tides.Murmansk, however, can boast that its embankments water rises four meters, while in the Gulf off the coast of St. Petersburg is a natural phenomenon barely noticeable, and then only in shallow waters.The main factor increasing expression tide, the water area is the relationship with the oceans.In the inland seas - the Black Sea, the Baltic Sea, Marmara, Mediterranean and especially the Azov - this phenomenon is almost non-existent.The level of water may rise to 5-10 centimeters, no more.
Another factor that may enhance the tide is indented coast.In the narrow bays with fine bottom of these phenomena are expressed more powerfully.If the mouth of the river is the eastern direction (opposite to the passage of the Moon), the tidal wave drives the water upstream, sometimes for a few tens of kilometers from the sea.Especially clearly expressed in the Amazon.Water rises to four meters.The wave moves inland at a speed of 25 km / h.
What affects the intensity of the phenomenon
Being long on the same beach, we notice that on different days of the tide is unequal power.At one time the sea comes ashore is very intense, and as far away from him.A week later, the tide has not differ so strongly.The reason lies in the action of the sun.We have already noted that the light also attracts the water column, although not as much as the Moon.Therefore, the geography of two types of tides - syzygy and neap.It all depends on the relative position of the moon and the sun relative to Earth.If the light and the satellite of our planet are on the same axis (called syzygy), hot flashes worse.When the sun and moon are arranged at right angles (quadrature), their effect on the attraction of water decreases.Then there is the lowest tide.
record holder
Where does occur greatest tides?The first place was shared by two geographical points.Both of them are located in Canada.It Ungava Bay to the north of the Bay of Fundy, and Quebec, between Nova Scotia and New Brunswick.There syzygy tide reaches eighteen meters!But when the Sun and Moon are in the area, the water level raising serious - fifteen and a half meters.In Europe, the greatest tide occurs in the city of Saint-Malo, in the French province of Brittany.Due to the nature of the coastline and the Channel flow natural phenomenon increases and the water reaches the height of 13.5 m.
third place at the height of the tide (almost thirteen meters) takes Penzhina Bay in the Sea of Okhotsk.This place is also a champion of the entire Pacific coast.Estuaries and the prevailing winds also bring about changes in the tides.Arkhangelsk, located at the confluence of the Northern Dvina in the sea, he knows such a thing as Manichaean.This is nothing like the tide.He chases the river water upstream.
tides in Murmansk
Mezen Bay of the White Sea also boasts a hardball arrival of water - as much as ten meters!However, in the port of Murmansk is the difference between the full and low water (the height of the end of the tide) is not as significant - just four meters.However, since the coast here shallow, gently sloping entrance to the sea, it exposed a large area.Tourists go specifically to watch the tide.Where a few hours ago raging waves, birds roam, looking at shellfish and crustaceans pits.A ship is not to run aground at the exit of the bay, the port authority has a special table, which is calculated when one or the other day begins tide, low tide.
Kola Bay
This is an amazing place in the Murmansk region.It washes over Nordkapp, which is an offshoot of the Gulf Stream.Thanks to the huge masses of warm water the sea is not frozen, but frost on the coast can reach temperatures of -24 and inland all -34 degrees.In fact, the Kola Bay - a fjord, crashing into the land of 60 kilometers.It ebbs and flows are enhanced power of the wind that blows towards the sea shores.The sea level at high water rises to four meters.
