1). Укажите, какие предложения соответствуют содержанию текста. Подтвердите свои ответы фактами из текста.

1. Igneous rocks have been formed by sedimentation.

2. Intrusive rocks have been formed by the cooling of rocks of the Earth's crust.

3. Extrusive rocks have been formed the same way.

4. The grain size of igneous rocks depends on mode of occurrence.

5. Exposed igneous rocks are numerous in mountain zones.

6. Granites and diorites belong to the group of extrusive rocks.

7. As a rule, granite may occur in dykes.

8. Pegmatites do not belong to the group of plutonic or intrusive rocks.

2). Ответьте на вопросы:

1. Have igneous rocks crystallized from magma or have they been formed by sedimentation?

2. Which types of igneous rocks do you know?

3. What does the grain size of igneous rocks depend on?

4. Can you give an example of intrusive or plutonic rocks?

5. Are diorites intrusive or extrusive formations?

6. What do you know about batholiths?

7. Do pegmatites belong to the group of plutonic or volcanic rocks?

8. How do pegmatites occur?

9. What minerals are igneous rocks rich in?

3. А) Найдите в правой колонке русские эквиваленты следующих слов в сочетаний слов:

1. adjacent layers а) способ залегания

2. abyssal rocks б) крупнозернистый

3. dimensions of crystals в) зоны крупных нарушений

4. valuable minerals г) абиссальные (глубинные) породы

5. shape and size of grains д) смежные пласты (слои)

6. mode of occurrence e) размеры кристаллов

7. coarse-grained ж) взбросы

8. uplifts з) форма и размер зерен

9. zones of major deformation и) ценные минералы

б) Найдите в правой колонке английские эквиваленты следующих сочетаний слов:

1. затвердевшие массы a) irregular shape

2. обломочные породы б) at a certain depth

3. медленно остывать в) economically important

4. мелкозернистый г) solidified masses

5. многочисленные трещины д) scientific value

6. неправильная форма e) to cool slowly

7. на определенной глубине ж) existing types of rocks

8. экономически важный з) fine-grained

9. научная ценность и) fragmentary rocks

10. существующие типы пород к) numerous cracks or fissures

Вариант 10

band - n слой; полоса; прослоек (породы); syn layer

cleave - v расщепляться; трескаться, отделяться по кливажу; cleavage n кливаж

constituent - n составная часть, компонент

define - v определять, давать определение

distribute - v (among) распределять (между); раздавать;

disturb - v нарушать; смещать

excess - n избыток, излишек; ant deficiency

flaky - а слоистый; похожий на хлопья

fluid - n жидкость; жидкая или газообразная среда

foliate - v расщепляться на тонкие слои; foliated - а листоватый, тонкослоистый; syn flaky

marble - n мрамор

mention - v упоминать, ссылаться; n упоминание

plate - n пластина; полоса (металла)

pressure - n давление; rock pressure (underground pressure) горное давление, давление горных пород

relate - v относиться; иметь отношение; related а родственный; relation - n отношение; relationship - n родство; свойство; relative - а относительный; соответственный

run (ran, run) - v бегать, двигаться; течь; работать (о машине); тянуться, простираться; управлять (машиной); вести (дело, предприятие)

schistose - a сланцеватый; слоистый

sheet - n полоса

slate - n сланец; syn shale

split (split) - v раскалываться, расщепляться, трескаться; syn cleave

trace - n след; tracing – n прослеживание

at least по крайней мере

to give an opportunity (of) давать возможность (кому-л., чему-л.)

in such a way таким образом

Metamorphic Rocks

The problem discussed concerns metamorphic rocks which compose the third large family of rocks. "Metamorphic" means "changed from". It shows that the original rock has been changed from its primary form to a new one. Being subjected to pressure, heat and chemically active fluids beneath the Earth's surface, various rocks in the Earth's crust undergo changes in texture, in mineral composition and structure and are transformed into metamorphic rocks. The process described is called metamorphism.

As is known, metamorphic rocks have been developed from earlier igneous and sedimentary rocks by the action of heat and pressure.

Gneisses, mica schists, phyllites, marbles, slate, quartz, etc. belong to the same group of rocks. Having the same mineral composition as granite, gneisses consist chiefly of quartz, orthoclase and mica. However unlike granite, they have a schistose structure. It means that their constituents are distributed in bands or layers and run parallel to each other in one direction. If disturbed the rock cleaves easily into separate plates.

The role of water in metamorphism is determined by at least four variable geologically related parameters: rock pressure, temperature, water pressure, and the amount of water present.

During a normal progressive metamorphism rock pressure and temperature are interdependent, and the amount of water and the pressure of water are related to the sediments and to the degree of metamorphism in such a way that, generally speaking, the low-grade metamorphic rocks are characterized by the excess of water. The medium-grade rocks defined by some deficiency of water and the high-grade metamorphic rocks are characterized by the absence of water.

Many of the metamorphic rocks mentioned above consist of flaky materials such as mica and chlorite. These minerals cause the rock to split into thin sheets, and rocks become foliated.

Slate, phyllite, schist and gneiss belong to the group of foliated metamorphic rocks. Marble and quartzite are non-foliated metamorphic rocks.

The structure of metamorphic rocks is of importance because it shows the nature of pre-existing rocks and the mechanism of metamorphic deformation. Every trace of original structure is of great importance to geologists. It gives an opportunity of analysing the causes of its metamorphism.

Being often called crystalline schists, metamorphic rocks such as gneisses and mica have a schistose structure. Metamorphic rocks represent the oldest portion of the Earth's crust. They are mostly found in the regions of mountain belts where great dislocations on the Earth once took place.