9. Answer the questions:

1. What does the Earth’s crust consist of? What main groups of rocks do you know?

2. What is the classification of rocks based on?

3. Do you know how sedimentary rocks have originated?

4. What does the name of igneous rocks depend on?

5. How were metamorphic rocks formed?

6. What fuels are often referred to as fossil fuels?

7. What is crude oil composed of?

8. What rocks are most abundant in fossil fuels?

9. How can natural forces influence rock formations and what effect does it have on drilling?

10. Speak about the Earth’s crust and the minerals it is composed of.

11. Translate the sentences paying attention to the conjunction either ... Or

1. Metamorphic rocks have been derived either from igneous or from sedimentary rocks.

2. Sediments are formed either at the surface or near the surface of the Earth by the action of water, heat and the remains of organisms.

3. Mechanical sediments such as gravel, sand, sandstone, shale can be either consolidated or unconsolidated.

4. Igneous rocks are formed as extrusive or as intrusive masses solidified either at the surface of the Earth’s crust or deep underground.

12. Complete the sentences using the given words:

consolidate consolidation consolidated unconsolidated

1. ... is the process of cementation of loose fragments of sedimen­tary rocks.

2. As it is known, sedimentary rocks ... under the pressure of overlaying beds.

3. Limestone, for example, is the ... rock which occupies vast areas of the Earth's surface.

4. Gravel, sand and clay form the group of ... mechanical sedi­ments, because they consist of loose uncemented particles.

stratify stratification stratified

1. Bedding or ... is the most characteristic feature of sedimentary rocks.

2. Crude oil is a ... deposit that has been developed from plant re­mains.

3. Coals ... by the decay of organic material.

4. As a result of physical, chemical or biochemical changes veg­etable remains are ... and changed into peat or coal, whereas micro-organisms remains changed into mineral oil.

accumulation accumulate accumulated

1. Fossil fuels were formed as a result of the ... of vegetable matter.

2. These fossil fuels are organic materials that ... in the geologic past.

3. Coal, for example, deposited from vegetable remains ... in swamp areas millions of years ago.

4. As it is known, any natural ... of mineral of some volume in the Earth's crust is a mineral deposit.

13. Put the verbs in brackets into the correct form, mind the Active and the Passive voice:

1. Geologists (to divide) the rocks of the Earth into three main types long ago. They (to divide) into sedimentary, igneous and metamorphic rocks.

2. Gravel, sand and clay (to form) the group of unconsolidated mechani­cal sediments. They (to form) by the destructive action of water and wind.

3. Scientists and engineers (to use) computers in their research work now. At the moment computers (to use) in different fields of science and engineering.

4. Materials for sedimentary rocks (to include) fragments of pre-existing rocks. Conglomerate, sandstone and shale (to include) into the group of sedimentary rocks.

5. Scientists (to observe) changes which take place deep in the Earth for many years. Many of these changes develop at such a slow rate that they (to observe) only since the appearance of modern equipment.