Complete the following sentences, using words and phrases from the text.

Extrusive igneous rocks occur at volcanic vents. Magma erupts as lava. (11)---------------. Basic lavas are rich in metallic elements. They flow easily and erupt gently. (12) ------------. Partial melting of peridotite forms basalt. (13)--------------. Basalt wells up from oceanic spreading ridges and builds new ocean floor.

Acid lavas appear at destructive plate margins. (14)-------------. They produce such rocks as dacite, rhyolite and obsidian.

Intermediate lavas stem from partial melting of certain minerals in subducted oceanic crust. (15)------------.

More than 850 known volcanoes have erupted in the last 2000 years. Those emitting continuously are active. (16)----------------. Volcanoes not erupting in recent years are dormants. (17)------------. Some volcanoes occur where colliding plates fused together.

a. Long-inactive volcanoes are said to be extinct.

b. Acid lavas are explosive and slow-flowing.

c. It cools and hardens quickly on the surface.

d. They may form a “Ring of Fire” around the Pacific Ocean.

e. The best-known product is basalt.

f. This process formed the lava – andesite.

g. It is the chief rock of the upper mantle

4.3 Listen to the lecture in geology at the Aberdeen University. The topic of the lecture is intrusive igneous rocks. Complete the following chart with the missing information.

Igneous Rocks- Intrusive

4.4. Listen to the lecture once more. Look at the diagram and describe the features produced by intrusive rocks, using the given definitions:

You will hear a short conversation. At the end of it, you will be asked several questions. The conversation will be spoken twice. After you hear a question, read the four selections and choose the one that is the best answer to the sentence the speaker asked. Answer all questions according to what is stated/implied in the conversation.

1. Where does this conversation take place?

A. museum

B. exhibition

C. geological College

D. class

2. What is another term for igneous rocks?

A. hot spots

B. lava rocks

C. fiery rocks

D. molten rocks

3. What is the main topic of the conversation?

A. rocks and minerals

B. igneous rocks

C. sedimentary rocks

D. metamorphic rocks

4. What is the formation process of magma?

A. melting, cooling and solidifying

B. cooling, melting and solidifying

C. rising, melting and cooling

D. melting, rising and cooling

5. What are silicates?

A. silicon and oxygen and aluminum

B. silicon and oxygen and a metal

C. silicon and oxygen and silicate

D. silicon and oxygen and mafiс mineral

6. What does quartz consist of?

A. silicate and a metal

B. silicate without a metal

C. silicate without oxygen

D. silicon and oxygen

7. What are the two people?

A. a teacher and a student

B. geologists

C. a guide and a visitor

D. husband and wife

DISCUSSION

TASK 1

Image a volcano and describe the development of it. You can use examples of different volcano eruptions (for example, St. Helen).

TASK 2

Here are 6 shapes of volcanoes: (R.P .-5.2)

1. loose-packed volcano

2. stratovolcano

3. caldera

4. rift volcano

5. spring hilltop

6. shield volcano

Describe one of them.

Fig. 28. Shapes of volcanoes

TASK 3

Look at the Volcano-cross-section (R.P – 5.1) and state what are the characteristic features.

WORDLIST

PRONUNCIATION

6.2 TERMS

UNIT 6

SEDIMENTARY ROCKS

COMPREHENSION

Vocabulary