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11. Most pegmatites are granitic in composition and consist of unusually large
crystals of quartz, feldspar, and muscovite.
12. Under normal conditions, the mantle is solid.

Task 2. Choose the correct preposition. Translate the sentences into
Ukrainian.
1. The liquid portion, called melt, is composed mainly from/of mobile ions of the
eight most common elements found in Earth’s crust.
2. Igneous rocks can be divided on/into broad groups according to their proportions
of light and dark minerals.
3. Coarse-grained rocks consist from/of a mass of intergrown crystals that are
roughly equal in size and large enough.
4. Granitic magma, which is rich in/on silica, may be extruded as an extremely
viscous mass.
5. Another group of igneous rocks is formed with/from the consolidation of
individual rock fragments that are ejected during a violent volcanic eruption.
6. The composition of most pegmatites is similar to/on that of granite.
7. The texture of an igneous rock refers to/on the overall appearance of the rock
based in/on the size, shape, and arrangement of its mineral grains.
8. On/in Sunday, May 18, 1980, the largest volcanic eruption to occur in North
America in historic times transformed a picturesque volcano into/on a decapitated
remnant.

Discussion

Task 1. Read and memorize the following words
approximate – бути дуже схожим, account for - пояснювати
наближатися
assume – зробити припущення sink – падати, тонути
carry out - проводити; виконувати; magmatic differentiation – магматична
здійснювати диференціація
depict – бути зображеним separate from – відокремлюватись від
findings – отримані дані

Task 2. Read the text. Translate it into Ukrainian. Talk about Bowen’s
reaction series and magmatic differentiation.

How Magmas Evolve

Because a large variety of igneous rocks exists, it is logical to assume that a
wide variety of magmas must also exist. However, geologists have observed that, over
time, a volcano may extrude lavas exhibiting quite different compositions. Data of this
type led them to examine the possibility that magma might change (evolve) and thus
become the parent to a variety of igneous rocks. To explore this idea, a pioneering
investigation into the crystallization of magma was carried out by N. L. Bowen in the
first quarter of the 20th century. In a laboratory setting Bowen and his co-workers
demonstrated that as a basaltic magma cools, minerals tend to crystallize in a systematic
fashion based on their melting points.
During the crystallization process, the composition of the remaining liquid
portion of the magma also continually changes. Bowen also demonstrated that if the
solid components of a magma remain in contact with the remaining melt, they will
chemically react and change mineralogy. For this reason, this arrangement of minerals
became known as Bowen’s reaction series. As you will see, in nature the earliest-

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