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Types of river outlets

Source: licencja: CC 0, [online], dostępny w internecie: www.pixabay.com.

Link to the lesson

Before you start you should know
  • the interior structure of the Earth;

  • the action of the Earth’s internal forces that shape its surface;

  • the action of mass wasting that shapes the surface of our planet;

  • how the wind affects the terrain.

You will learn
  • to explain what a river delta is, and in what conditions it is created;

  • to explain what an estuary is, and in what conditions it is created;

  • to determine the type of a river outlet based on a map or satellite image.

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Nagranie dźwiękowe abstraktu

Types of river outlets

A river may flow into another one, thus becoming its tributary. The transported rock material is then taken over by the main river. When the outlet is on the shore of a sea or lake, the river at that places loses its ability to transport sediments, and all material accumulates. When the sea (or lake) is shallow in that place, and there are no strong coastal currents or high tides, the rock material brought by the river is accumulated on the shore of the reservoir and gradually backfills the outlet, forming an alluvial fan called a deltadeltadelta.

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Determine on which continent the randomly selected river is, and into which sea or ocean it flows (tu uzupełnij).
Source: licencja: CC 0.

In some places, rivers flow into a deep, open sea. In addition, strong sea currents and high tides often occur in such places. The sediments brought by the river are carried out to sea and deposited in the depths far from the shore. The outlet of the river does not become backfilled, and the riverbed expands not due to river erosion, but due to repeated falling tides and rising tides that sometimes reach far upstream. Rising and falling tides are erosive and widen the outlet, at the same time preventing accumulation of the material carried by the river. Because of their shape, in Poland they have been called funnel outletsfunnel outletfunnel outlets, and in the rest of the world – estuariesestuaryestuaries from the Latin term aestuarium which originally meant ‘seaway’. In many cases, river outlets have a form that is intermediate between a delta and an estuary.

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Exercise 1
Move the characteristic features of river outlets to the corresponding groups. river delta Możliwe odpowiedzi: 1. occurs when a river flows into a shallow lake or sea, 2. the rock material brought by the river is not accumulated on the shore of the reservoir, 3. occurs when a river flows into a deep sea, 4. has the form of two or more legs, 5. the rock material brought by the river is accumulated on the shore of the reservoir, 6. has the form of a funnel widened by sea tides, 7. is created in an area with strong coastal currents and high tides, 8. is created in an area where there is a lack of strong coastal currents and high tides estuary Możliwe odpowiedzi: 1. occurs when a river flows into a shallow lake or sea, 2. the rock material brought by the river is not accumulated on the shore of the reservoir, 3. occurs when a river flows into a deep sea, 4. has the form of two or more legs, 5. the rock material brought by the river is accumulated on the shore of the reservoir, 6. has the form of a funnel widened by sea tides, 7. is created in an area with strong coastal currents and high tides, 8. is created in an area where there is a lack of strong coastal currents and high tides

Keywords

river outlet, estuary, funnel outlet, delta

Glossary

delta
delta
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Nagranie dźwiękowe słówka

delta - ujście rzeki w postaci dwóch lub więcej odnóg na obszarze usypanym z osadów przyniesionych przez rzekę

estuary
estuary
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Nagranie dźwiękowe słówka

estuary - poszerzone przez pływy morskie ujście rzeki uchodzącej do głębokiego morza, powstające w miejscach, w których występują silne prądy przybrzeżne

funnel outlet
funnel outlet
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Nagranie dźwiękowe słówka

patrz estuaryestuaryestuary