Lexical exercises. a) Complete the sentences

a) Complete the sentences:

1. Oxygen and silicon are the two most.... elements in the crust and mantle.

2. When temperature and pressure drop sufficiently, magma.... to form solid igneous rocks.

3. An intrusive igneous rock forms when magma solidifies within....

4. Geologists use both.... and.... to classify and name igneous rocks.

5..... is a volcanic rock intermediate in composition between basalt and granite.

6. Granites are the most.... rocks in continental crust.

7. A granite magma rises through the Earth’s crust and may.... from a volcano to form rhyolite.

b) Write out the equivalents in pairs:

1. Alter; comprise; total; effect; composition; speed; gravitation; spring.

2. Velocity; change; complete; include; attraction; influence; fountain; structure.

c) Translate the sentences into Russian:

1.Экструзивные изверженные породы образуются, когда магма извергается и затвердевает на земной поверхности.

2. Интрузивные изверженные породы образуются, когда магма затвердевает внутри коры.

3. Изверженные породы иногда называют плутоническими породами.

4. Два наиболее распространенных типа изверженных пород в земной коре – это гранит и базальт.

6. Summary.

Geologists separate rocks into three classes based on how they form: igneous rocks, sedimentary rocks, and metamorphic rocks. Igneous rocks form when a hot, molten liquid called magma solidifies.

Three different processes – rising temperature, lowering of pressure, and addition of water – melt portions of the Earth’s asthenosphere. These processes form great quantities of magma in three geologic environments: spreading centers, mantle plumes, and subduction zones. The temperature of magma varies from about 600° to 1400° C. Nearly all magmas are silicate magmas. Magma usually rises toward the Earth’s surface because it is of lower density than rocks that surround it.

An extrusive, or volcanic, igneous rock forms when magma erupts and solidifies on the Earth’s surface. An intrusive, or plutonic, rock forms when magma cools and solidifies below the surface. Plutonic rocks typically have medium- to coarse-grained textures. Volcanic rocks commonly have very fine- to fine-grained textures.

The two most common types of igneous rocks in the Earth’s crust are granite, which comprises most of the continental crust, and basalt, which makes up oceanic crust. The upper mantle is composes of peridotite.

An igneous rock is classified and named according to its texture and mineral composition.

Unit VI SEDIMENTARY ROCKS