The hydrosphere

   1. Oceans

   Almost three-quarters of the Earth is covered with oceans and seas. We distinguish five oceans:
   - Pacific ocean between America and Asia, it is the largest ocean of the Earth. it extend from the Arctic Circle and the Antarctic Circle.
   - Atlantic Ocean is between the Americas and Europe and Africa. It connects to the Polar circles on the North and South.
   - Indian Ocean, located in Southern Asia, between Africa and Oceania.
   - Glacial Arctic Ocean in the north polar zone.
   - Glacial Antarctic Ocean in the south polar zone.

 2. Choose one continent and answer: Pacific, Atlantic, Indian, Arctic and Antarctic

Between Europe and America

It is on South Asia

Between America and Asia

In the North Pole zone

Between America and Africa

In the South Pole zone

The largest of the Earth

Between Africa and Oceania

    3. Properties of seawater

   The oceans and seas contain 23 grams of salt (sodium chloride) per 1000 grams of water.

   The dissolved salt content of a body is called salinity. Cold seas are usually less salty than warm seas.

   The water temperature depends on the depth. In the superficial layers, it is similar to the Earth. But from 200 meters depth, temperature remains unchanged about 2 degrees above zero. In the polar zones, a big layer of ice is formed on the sea surface.

    4. Movements of Seawater

   Seawaters move forming waves, tides and currents.

   - The waves are wave motions of the sea surface. Some of them are caused by wind and others are caused by coastal earthquakes or by submarines. In the latter case, it is formed a large and isolated wave that sweeps along what appears in its path and produces intense damages.

   - Tides are periodic rises and falls of sea water level caused by the attraction of the Moon and the Sun. Each day two rises of sea level occurs (high tide) and two falls of sea level also occur (low tide). The Most high tide occurs when the Sun, Earth and Moon are in the same direction. The attraction of the moon is more intense than the Sun, which is farther from the Earth.

   - The currents are like rivers within the ocean. The currents are caused by the wind, the temperature differences (from the coldest to the warmest seas), the salinity (from the more salty to less salty sea), the movement of rotation of the earth, etc.

   5. Choose one of these words and answer: waves, tides and currents:

They are like rivers within the sea

Because of the attraction of the Sun and Moon

They are produced by an earthquake

There are high tide and low tide

They go from cold to warm seas

They produce intense damage

    6. The coast

   The contact area between the sea and the continent is called coast. When it is flat and sandy, it forms the beach and it is called flat coast. When it is mountainous is called cliffed coast.

   The islands are pieces of land surrounded by water. For example: Mallorca.

   The archipelago is a group of nearby islands. For example: the Balearic Islands in Spain.

   The cape is a pronounced projection of the littoral. For example: Cape Horn in Argentina.

   The gulf is an inlet of the sea on the littoral. For example: the Gulf of Guinea in Africa.

   The bay is a small gulf. For example: the bay of Cadiz in Spain.

   The strait separates two continents or two islands. For example: the Strait of Gibraltar between Africa and Europe.

   8. Answer with the right word: island, gulf, strait, archipelago, cape or bay

Lot of land surrounded by water

it separates two continents

Inlet of the sea on the littoral

The Gibraltar

The Guinea


A set of islands

Projecting of land in the headland at sea

A small gulf

The Balearic

The Cadiz

The Horn


   7. Rivers

   It is a water course originated in the mountains and goes towards another river, lake or sea. It runs through a channel. The tributaries are rivers that flow into the main river.
   Watershed is the land area whose water discharged into the same river. All the rivers that flow into the same sea belong to the same slope.
   The river has several parts:
   - The high course, near the source, when it goes over mountainous areas with great force and speed, it drags soil and stones and causes severe erosion.
   - The middle course, the slope is smaller, the water descends more slowly. The river sweeps along the materials resulting from in the high course.
   - the low course, the river flows slowly, producing meanders (waves of the course) and the materials are deposited in the mouth. It can produce a river delta.

   9. Indicate the course of the river: high, middle or low

Materials are deposited

It is near the source

The slope is smaller

The materials are deposited in the mouth

It has great speed

It drags the materials

It can produce a river delta

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®Arturo Ramo García.-Record of intellectual property of Teruel (Spain) No 141, of 29-IX-1999
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