- •Contents
- •Introduction
- •Unit 1 The Science of Geology
- •Different Areas of Geologic Study
- •Grammar focus The Noun in English
- •Discussion
- •Individual work
- •The Earth system
- •Energy for the Earth system
- •Test yourself
- •Unit 2 The Rock Cycle
- •The rock cycle
- •Grammar focus The Degrees of comparison of adjectives
- •Discussion
- •Lithosphere, mantle, layers, core, crust
- •Individual work
- •Earth’s Mantle
- •Earth’s Core
- •Test yourself
- •Unit 3 The Face of Earth
- •Grammar focus The Adverb in English
- •Discussion
- •Oceanic (mid-ocean) ridges, mountain belts, ocean basins, continental margins, continents, stable interior
- •Individual work
- •Test yourself
- •Unit 4 magma Part 1
- •Origin of Magma
- •Grammar focus Prepositions in English
- •Discussion
- •How Magmas Evolve
- •Individual work
- •Assimilation and Magma Mixing
- •Partial Melting and Magma Composition
- •Test yourself
- •Unit 5 magma Part 2
- •Intrusive Igneous Activity
- •Grammar focus The Present Indefinite and the Past Indefinite Tenses
- •Discussion
- •Massive Intrusive Bodies: Batholiths, Stocks, and Laccoliths
- •Individual work
- •Mineral Resources and Igneous Processes
- •Magmatic, igneous, vein deposits, metal-rich, hydrothermal solutions, disseminated deposit
- •Test yourself
- •Volcanic eruptions
- •The Nature of Volcanic Eruptions
- •Grammar focus The Past Indefinite Tense
- •Discussion
- •Why Do Volcanoes Erupt?
- •Individual work
- •Materials Extruded during an Eruption: lava
- •Test yourself
- •Volcanic structures and eruptive styles Part 1
- •Anatomy of a Volcano
- •Grammar focus The Present Indefinite versus the Future Indefinite tenses in complex sentences
- •Discussion
- •Types of volcanoes
- •1. Shield Volcanoes
- •2. Cinder Cones
- •3. Composite Cones
- •Individual work
- •Materials Extruded during an Eruption: gases and pyroclastic materials
- •Test yourself
- •Other Volcanic Landforms
- •Grammar focus The Continuous tenses
- •Discussion
- •Plate Tectonics and Volcanic Activity
- •Individual work
- •Test yourself
- •Weathering and Soil
- •Weathering
- •Grammar focus Perfect Tenses
- •Discussion
- •Mechanical Weathering
- •Individual work
- •Chemical Weathering
- •Test yourself
- •Internal processes, mass wasting, external processes, erosion, weathering
- •Grammar focus The Passive Voice (1)
- •Discussion
- •Controls of Soil Formation
- •Individual work
- •Soil Erosion
- •Test yourself
- •Sediment, type of vegetation, rock cycle, rate of soil, soil erosion
- •Unit 11 mineralogy Part 1
- •Grammar focus The Passive Voice (2)
- •Discussion
- •Characteristics of minerals
- •Individual work
- •Physical Properties of Minerals Optical Properties
- •Test yourself
- •Unit 12 mineralogy Part 2
- •Mineral Strength
- •Grammar focus
- •Indirect Speech
- •Discussion
- •Density and Specific Gravity
- •Individual work
- •Other Properties of Minerals
- •Test yourself
- •Unit 13 mineral groups
- •Grammar focus Modals in English
- •Discussion
- •Common silicate minerals
- •Individual work
- •Important nonsilicate minerals
- •Mineral resources
- •Test yourself
- •Unit 14
- •Igneous rocks Part 1
- •Magma: The Parent Material of Igneous Rock
- •The Nature of Magma
- •Grammar focus
- •Infinitive
- •Discussion
- •Igneous Processes
- •Igneous Compositions
- •Individual work
- •Other Compositional Groups
- •Test yourself
- •Unit 15
- •Igneous rocks Part 2
- •Igneous Textures: What Can They Tell Us?
- •Types of Igneous Textures
- •Grammar focus Gerund
- •Discussion
- •Felsic (Granitic) Igneous Rocks
- •Intermediate (Andesitic) Igneous Rocks
- •Individual work
- •Mafic (Basaltic) Igneous Rocks
- •Pyroclastic Rocks
- •Test yourself
- •Unit 16 metamorphism and metamorphic rocks
- •What Is Metamorphism?
- •Grammar focus Participle
- •Individual reading
- •Common Metamorphic Rocks Foliated Rocks
- •Nonfoliated Rocks
- •Test yourself
- •Sedimentary, pressure, mineralogical, metamorphism
- •Vocabulary
- •Glossary
- •List of reference books
The Nature of Magma
Magma is completely or partly molten rock, which on cooling solidifies to form an igneous rock composed of silicate minerals. Most magmas consist of three distinct parts—a liquid component, a solid component, and a gaseous phase. The liquid portion, called melt, is composed mainly of mobile ions of the eight most common elements found in Earth’s crust—silicon and oxygen, along with lesser amounts of aluminum, potassium, calcium, sodium, iron, and magnesium. The solid components (if any) in magma are silicate minerals that have already crystallized from the melt. As a magma body cools, the size and number of crystals increase. During the last stage of cooling, a magma body is like a “crystalline mush” with only small amounts of melt. The gaseous components of magma, called volatiles, are materials that will vaporize (form a gas) at surface pressures. The most common volatiles found in magma are water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2), which are confined by the immense pressure exerted by the overlying rocks. These gases tend to separate from the melt as it moves toward the surface. As the gases build up, they may eventually propel magma from the vent. When deeply buried magma bodies crystallize, the remaining volatiles collect as hot, water-rich fluids that migrate through the surrounding rocks. These hot fluids play an important role in metamorphism.
Task 3. Answer the following questions, using the vocabulary from Task 1.
When are igneous rocks formed?
What is magma?
What is lava?
How does magma differ from lava?
Lava is emitted in two ways. What are they?
What are three distinct parts of magma?
What is the name of the liquid portion of magma? What is it composed of?
The solid components in magma are silicate minerals, aren’t they?
What is the name of the gaseous components of magma?
What are the most common volatiles found in magma?
When deeply buried magma bodies crystallize, the remaining volatiles collect as hot, water-rich fluids, don’t they?
Task 4. Complete the following sentences from the text in Task 3.
… is composed mainly of mobile ions of the eight most common elements found in Earth’s crust.
The solid components (if any) in magma are … minerals.
The gaseous components of magma are called … .
The most common volatiles found in magma are … .
When deeply buried magma bodies crystallize, the remaining volatiles collect as … that migrate through the surrounding rocks.
Task 5. Find English equivalents for the following (see the text). Try to build up your own sentences with them.
Вулканічні гірські породи; траплятися на різних рівнях земної кори; підніматися до поверхні; виверження попілу; частково розплавлена гірська порода; утворюватись (складатися) з силікатів; тверда речовина (твердий компонент); кристалізуватися з розплавленої речовини; остання стадія охолодження; кашоподібна речовина, що має кристалічну структуру; мати тенденцію відокремлюватись від розплавленої речовини; виштовхувати магму з повітряного клапану.
Task 6. Give a short summary of the text from Task 2.