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Learn about concepts of geography, find geographic information, maps, videos and more.
Tides Tides are the rise and fall of sea levels. Roughly every 12 hours, the oceans on each side of the globe rise a little and then fall back. These tides are caused by the combined effects of the gravitational forces between the rotation of the Earth and the Moon and the Sun.
Spring Tides When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides. They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon. Neap Tides During the moon's quarter phases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another. Neap tides occur during quarter moons.
The total eclipse of the sun. Tens of thousands of tourists, scientists and astronomers gathered in northern Australia on 14 November 2012 to glimpse a rare total solar eclipse.
The eclipse, which occurs when the moon passes between the Earth and the sun, plunged parts of Queensland into darkness for just over two minutes. Watch also the next video.
Eustatic sea-level rise is the world-wide changes in sea level over decades to centuries. The change of the sea-level occurs everywhere throughout the world, due not to a movement of the land but to an actual fall or rise of the ocean itself.
Eustatic sea-level rise is the world-wide changes in sea level caused by the addition of water from the melting of glacial ice and/or the thermal expansion of sea water due to global warming.
The graph illustrates the sea-level curve in last 210 million years, with the high levels representing marine transgressions and the low levels representing marine regressions. Marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously exposed land.
The Port of Rotterdam is the largest port in Europe, located in the city of Rotterdam, Netherlands.
Rotterdam mainport is Europe's logistical centre with an infrastructure catering to all transport modalities. It consists of different distinct port areas and distriparks that facilitate the needs of a hinterland with 40,000,000 consumers.
From 1962 until 2004 it was the world's busiest port, now overtaken by first Shanghai and then Singapore.
In 2009, Rotterdam was the world's tenth-largest container port in the world.
In 2011 Rotterdam was the world's fifth-largest port in terms of annual cargo tonnage. Covering 105 square kilometres, the port of Rotterdam now stretches over a distance of 40 kilometres.
The port of Rotterdam consists of:
the city centre's historic harbour area, including Delfshaven;
the Maashaven / Rijnhaven / Feijenoord complex;
Waalhaven;
Vondelingenplaat;
Eemhaven;
Botlek;
Europoort, situated along the Calandkanaal, Nieuwe Waterweg and Scheur (the latter two being continuations of the Nieuwe Maas); and
The reclaimed Maasvlakte area, which projects into the North Sea.
Geography is the study of natural and human constructed phenomena from a spatial perspective. Geography has two main sub disciplines: Human geography Human geography includes such subjects as demography, human settlements, transportation, recreation and tourism, resources, religion, social traditions, human migration, agriculture, urban systems, and economic activities.
Physical geography Physical geography is concerned with the study of the Earth’s atmosphere, biosphere, hydrosphere, and lithosphere from theoretical and applied viewpoints.
The Netherlands is a geographically low-lying country. About 27% of The Netherlands and 21% of its population located below sea level, and 50% of its land lying less than one metre above sea level.
Most of the areas below sea level are man-made, caused by centuries of extensive and poorly controlled peat extraction, lowering the surface by several meters. Even in flooded areas peat extraction continued through turf dredging. From the late 16th century land reclamation started and large polder areas are now preserved through elaborate drainage systems with dikes, canals and pumping stations. Much of the Netherlands is formed by the estuary of three important European rivers, which together with their distributaries form the Rhine-Meuse-Scheldt delta.
The Delta Works The Delta Works is a series of construction projects in the southwest of the Netherlands to protect a large area of land around the Rhine-Meuse-Scheldt delta from the sea.
The Delta Works consist of dams, sluices, locks, dikes and storm surge barriers.
Dams
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water.
Example of a dam: The Haringvlietdam.
Sluices A sluice (from the Dutch word "sluis") is a water channel controlled at its head by a gate. Sluice gates commonly control water levels and flow rates in rivers and canals. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway.
Example of a sluices: The sluices of the Eastern Scheldt storm surge barrier.
Locks A lock is a device for raising and lowering boats between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is the chamber itself (usually then called a caisson) that rises and falls. Locks are used to make a river more easily navigable, or to allow a canal to take a reasonably direct line across land that is not level.
Example of a lock:
Dikes
The modern word dike or dyke most likely derives from the Dutch word "dijk". Dyke or dike may refer to: a natural or artificial slope or wall to regulate water levels. A dike is called levee in American English. A dike / levee is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines.
Example of a dike:
Storm surge barriers
A storm surge barrier is designed to protect the Netherlands from flooding. The aim of the storm surge barriers is to shorten the Dutch coastline, therefore reducing the number of dikes that had to be raised. The Eastern Scheldt storm surge barrier (de Oosterscheldekering), between the islands Schouwen-Duiveland and Noord-Beveland, is the largest of the 13 Delta works series of dams, designed to protect the Netherlands from flooding. The construction of the Delta Works was in response to the Flood of 1953. The Oosterscheldekering was initially designed, as a closed dam, but after public protest huge sluice-gate-type doors were installed. Thesesluice-gate-doors are normally open, but can be closed under adverse weather conditions. In this way the saltwater marine life behind the dam is preserved and fishing can continue, while the land behind the dam is safe from the water.
Example of a storm surge barriers (TheEastern Scheldt storm surge barrier):
The "Maeslantkering" is the final protection work of the Deltaworks. Situated in the main access channel of the Port of Rotterdam it is usually in open condition. It has been designed to withstand a severe storm occurring once every 50 years. Example of a storm surge barriers (The Maeslantkering storm surge barrier near Rotterdam during a test closure):
The aim of the dams, sluices, and storm surge barriers was to shorten the Dutch coastline, therefore reducing the number of dikes that had to be raised.
