Put the facts in the correct order which shows how sea floor spreading develops

1. Fresh cracks appear.

2. Mantle upwells.

3. It partly melts.

4. Molten rock plugs gaps.

5. Tension pulls old crust apart.

6. New crustal blocks subside.

7. Mantle pushes up the oceanic crust.

8. Molten rock rises through cracks.

9. Bulging plate splits.

10. The process is repeated.

11. A central block subsides.

LISTENING COMPREHENSION

You will hear part of a radio report about the oceanic crust. For statements 1-12, complete the notes, which summarize what the speaker says. You will need to write a word or short phrase in each sentence. You will hear the recording twice.

1. The oceanic crust is different from_______________________.

2. Besides aluminum and calcium, ocean crust has a high content of_______________.

3. The combination is called ____________________.

4. The ocean crust has _____________________.

5. The first layer consists of __________________________.

6. They may be _______________________, which lie up on ________________.

7. The next layer is mainly _____________________, which is found at ___________________________.

8. The third layer is made up of _____________________.

9. While the last layer is ________________________.

10. It is made up of peridotite, chiefly __________________.

6. DISCUSSION (R.P – 8.1.5)

We’ll discuss the subject: «Plate tectonics in action». Pay attention to the words and expressions and pronunciation of some of the geographical names. Read the text, which will give you some necessary information. Use the earlier communicative formulas (Unit 7). Pay special attention to the questions, which will help you to underline what facts are more important.

Use the diagrams – «Plate tectonics in action», «Tectonic plates». (R.P. 8.2.10,8.2.11)

Geographical Names

Eurasian Plate	Indo-Australian Plate	Nazca Plate
African Plate	Pacific Plate	South American Plate
Antarctic Plate	North American Plate

restless	непрекращающийся, неугомонный
jigsaw puzzle	картинка-головоломка, мозаика
abutting	примыкающий, прилегающий
diverging	расходящийся
colliding	сталкивающийся
slab	кусок, плита, блок
tectonic plate	тектоническая плита
coupled to	связанный / соединенный с
rigid	устойчивый, твердый
to ride upon	передвигаться / скользить по (поверхности)
convection current	конвективный поток
to shift	перемещать, сдвигать
margin -constructive -destructive -conservative -passive -active	граница -конструктивная -деструктивная -консервативная -пассивная -активная
lithosphere	литосфера
zone -collision -subduction	зона -столкновения -субдукции
spreading ridge	спрединговый хребет
to dive down	погружаться, нырять
to slide past	скользить мимо
to spark off	вызывать, порождать
boundary	граница, поверхность раздела
permutation	изменение
interlock	смыкаться

EARTH’S CHANGING SURFACE

Our planet’s solid surface is a restless jigsaw of abutting, diverging and colliding slabs called plates (lithospheric plates). How plates behave forms the subject known as plate tectonics.

Each plate involves a slab of oceanic crust, continental crust, or both, coupled to a slab of rigid upper mantle. Collectively these plates make up the lithosphere. This rides upon the asthenosphere, a dense, plastic layer of the mantle. Heat rising through this layer from the Earth’s core and lower mantle seemingly produces convection currents that shift the plates above.

Plate activities produce three main kinds of plate margins.

· Constructive (divergent) margins are oceanic spreading ridges where new lithosphere is formed between two separating oceanic plates.

· Destructive (convergent) margins are oceanic trenches where an oceanic plate dives down below a (less dense) continental plate.

· Conservative (transform) margins are where two plates slide past each other and lithosphere is neither made nor lost.