Unit 2. Relief and waters on the Earth

1. What is the Earth made of?

1.1 The structure of the Earth

The Earth is divided into layers:

The crust is the surface layer. It is a thin, solid layer made of rock.The mantle is the intermediate layer. This layer is almost 85% of the Earth's volume.It includes magma, which is molten rock.The core is the deepest layer. The core is part solid and part liquid.

The Earth's temperature increases with depth. The temperature in the core reaches about 4.500º C.

The Earth's crust has a solid part ( continents) and liquid part (oceans)

The continents are large land masses, surrounded by oceans and seas . There are six continents . In order of size , they are Asia, America, Africa, Antarctica, Europe and Oceania.

The oceansOceans are large masses of salt water. There are five oceans. In order of size, they are the Pacific, the Atlantic, the Indian, the Southern and the Arctic.

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Tectonic plates

The Earth´s crust is divided into different places called tectonic plates. These plates are in continuous movement. They move slowly at a speed of two to ten centimetres per year. Some plates move apart , while others collide. The collision of plates has produced many mountains.

2. WHAT IS THE EARTH´s RELIEF?

The Earth's surface is not flat. There are different kinds of relief.

Continental relief

1. Mountains are high landforms with step sides. The world's highest mountain range is the Himalaya in Asia.

2. Valleys are areas of low land between mountains. 3. Plains are low, flat areas of land. Large plains are often found on the coast , and are

formed by large rivers.4. Plateaus are large and high plains. The highest plateau is in Tibet in Asia.5. Basins are natural depressions, of low areas of land . Some are below sea level.

Coastal relief.

1. A peninsula is an area of land surrounded by water on all sides except one.2. A cape is a part of the coast which extends into the sea.3. A gulf is a large area of a sea or ocean partially enclosed by land. A bay is a small

gulf.4. And island is an area of land surrounded by water on all sides.5. Archipelago is a group of islands.

Coats can be flat and low-lying or high• Beaches are in flat coastal areas.• Cliffs are in high coastal areas.

Oceanic relief.

The ocean floor is irregular. I ts rel ief is similar to continental relief.1. Continental shelves are near coastlines. These shelves are vast plateaus which reach a depth of 150 meters. 2. Continental slopes lead down to the deeper part of the oceans.3. Ocean ridges are large mountain ranges under the water. They rise up to 3000 meters from the ocean floor.

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4. Abyssal plains are large and deep underwater plains which reach a depth between 3000 and 5000 meters.

5. Ocean trenches are large, deep depressions in the ocean floor. The deepest ocean trench is Challenge Deep in the Pacific Ocean

3. WATER

3.1 Water on Earth.

We can distinguish two groups a. Salt water or sea water is found in oceans and seasb. Fresh water is found in rivers , lakes, glaciers, groundwaters and at the poles.

3.2 The water cycle.

Water is always moving and changing its physical state. This process is called the water cycle.There are several stages in the water cycle

3.3 FRESH WATWER

a. Rivers Rivers are freshwater body that flows towards the sea, ocean, lake or another river. The place where river begins is called its source Rivers carry water down to the sea . Smaller rivers flowing into a larger river are called tributaries.The area occupied by a river and its tributaries is called a basinThe flow of a river refers to the amount of water it carries. Parts of a river are:

1. Upper course. The river is quite steep, so water flows with energy and removes rocks and soil. The river carves canyons or V-shaped valleys. Waterfalls can be formed there.

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2. Middle course . The river is lower down and its slower. It transports the eroded materials . The landforms are wide shallow valley and meanders.

3. Lower course The river flows very slow so the material is deposited. The main landforms are wide flat valleys , estuaries and deltas.

b. Lakes are bodies of water surrounded by land. Lakes contain mainly freshwater however there are some lakes with salt water as Mar Caspio.

c. Groundwaters

Groundwaters run and are stored under the ground. It represents 25% of the water on the continents. Most groundwaters come from rainfall. Groundwater forms aquifers and underground rivers and lakes.

d. Glacier

Glaciers are large masses of ice formed by accumulation of snow. Most glaciers are :1. Polar cap2. High mountains

Glacier ice is the largest reservoir of freshwater on the Earth

3.4 SALT WATER

It is oceans and seas´ water . Oceans and seas´water are in permanent movement . There are three types of movements:1. Ocean currents are large masses of water. similar to rivers. Currents can be warm or

cold.2. Tides are the daily rise and fall of the water level caused by attraction of the Moon and

the Sun.Tides can be high tide and low tide.3. Waves are undulations of the surface of the produced by wind.

Oceans and seas hold almost all the world´s liquid water.

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EXERCISES.

1. Define: ocean, continent, mountain.2. Write the three main layers of the Earth.3. Write the name of oceans and continents 4. Complete the sentences below:

a. The deepest Earth´s layer _________________________b. Human life develops in ___________________________c. Earth´s intermediate layer is _______________________d. Crust is broken in portions called ___________________e. A low zone between mountains is a _________________f. S l o p e t h a t s e p a r a t e s c o n t i n e n t a l s h e l f f r o m a b y s s a l p l a i n s

_____________________g. Underwater mountains are called ___________________h. Relief is mad by ________________________________i. Mantle includes ______________ which is molten rock.

5. Answer the next questions:

a. Which is the deepest layer ?b. Which layer is made of molten rock?c. Which layer reaches about 4500 Km?d. How many continents are there?e. What are the name of the continents?f. What is the difference between a plateau and a plain?

6. Say if next sentences are true or false?

a. Basins are always under sea level .b. Abyssal plains are from 200 metresc. Europe and Asia are part of the same continent land mass.d. Tectonic plates are Earth´s portions surrounded by water on all sidese. The largest ocean in the world is the Pacific ocean.f. Cliffs are in flat coastal areas.g. Atlantic Ocean is the biggest and deepest ocean.h. A cape is a part of the coast which extends into the seai. A peninsula is an area of land surrounded by water on all sides.

7. Correct the sentence:

a.Most of the Earth’s oceans are in the northern hemisphere, while most of the land masses are in the southern hemisphere.

b.There are six oceans in the world.c. Mountains are high landforms with step sides. The world's highest mountain range is the

Himalaya in Asia.d.Ocean trenches are large, deep depressions in the ocean floor. The deepest ocean

trench is Challenge Deep in the Indian Ocean

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8. Write the main phases of the water cycle.

9. Say if next sentences are true or false . Make the right sentence.a. Rivers begin in a place called course .b. River is a freshwater body that flows toward the sea or another river.c. Tributary is a smaller river that flows into a larger river.

10. What are the sentences describing?

a. The river is lower down and its slower. It transports the eroded materials and foms meanders

b. They are produced by the action of the wind on the surface of the water.b. The Moon’s gravitational pull produces them.c. They are large masses of ice formed by accumulation of snow.c. The time in a day when the level of the sea on the coast is at its lowestd. They can be warm or cold and move like big rivers across oceans.

11.Choose the correct word to complete each sentence:a. An ocean is bigger/smaller ___________ than a sea.b. An ocean ridge is lower/higher __________ than a trench.c. The upper course of a river flows slower/faster __________ than themiddle course.d. The Antarctic Ocean is warmer/colder __________ than the PacificOcean.

12.Indicate the course of the river (upper, middle, or lower) depending the characteristics.

a. It has a lot of meandersb. The river is quite steep .c. The main landforms are wide flat valleys , estuaries and deltas.c. It is the highest part of the river.d. Waterfalls can be formed there.

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13. Locate the main rivers in the world: Mississippi-Missouri River, Amazon River, Congo River, Niger River, Nile River, Danube River, Volga River, Lena River, Ob River, Yenisey River, Yantze River, Huang River

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14. Write the name of the main landforms.

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