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melt ice. That is, volatiles cause rock to melt at lower temperatures. Further, the effect
of volatiles is magnified by increased pressure. Deeply buried “wet” rock has a much
lower melting temperature than “dry” rock of the same composition (see Figure 4.1).
Therefore, in addition to a rock’s composition, its temperature, depth (confining
pressure), and water content determine whether it exists as a solid or liquid.
In summary, magma can be generated in three ways: (1) when an increase in
temperature causes a rock to exceed its melting point; (2) in zones of upwelling a
decrease in pressure (without the addition of heat) can result in decompression melting;
and (3) the introduction of volatiles (principally water) can lower the melting
temperature of hot mantle rock sufficiently to generate magma.

Task 4. Answer the following questions, using the vocabulary from Task 1.
1. Where does most magma originate?
2. What is the geothermal gradient?
3. How does increase in temperature influence the origin of magma?
4. Describe decompression melting.
5. How does the introduction of volatiles trigger melting?
6. What are the three ways magma can usually be originated in?

Task 5. Find English equivalents for the following (see the text). Try to
build up your own sentences with them.
Породжуватись (створюватись) у самому верхньому шарі мантії; переходити у
мантію; межі тектонічної плити; тверда, а не рідка гірська порода; залишатись
глибоко в Землі; зовнішнє ядро Землі; верхня мантія Землі; точка (температура)
плавлення; значно відрізнятись; за звичайних умов; зменшувати температуру;
вміст води; тиск, який зростає з глибиною; визначати; зони апвелінгу; достатньо.

Task 6. Give a short summary of the text from Task 3.

Grammar focus
Prepositions in English

Task 1. Translate the sentences into Ukrainian paying special attention to
special prepositions after some verbs, nouns and adjectives.
1. The formation of bauxite depends on climatic conditions in which chemical
weathering and leaching are pronounced.
2. Mining is preceded by the removal of tropical vegetation, thus destroying
rainforest ecosystems.
3. The long-term consequences of bauxite mining are clearly of concern for
developing countries in the tropics, where this important ore is mined.
4. Weathering also contributes to the formation of some of Earth’s most spectacular
scenery.
5. All materials are susceptible to weathering.
6. Weathering is the response of Earth materials to a changing environment.
7. The mass of crystalline rock is now subjected to a very different and
comparatively hostile surface environment.
8. Igneous rocks are divided into broad compositional groups based on the
percentage of dark and light silicate minerals they contain.
9. The demand for metallic natural resources has increased exponentially in recent
years.
10. In granitic magmas the residual melt can become enriched in rare elements and
some heavy metals.

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