Unit I geology and the Earth

Unit I GEOLOGY AND THE EARTH

 

P a r t I

 

Read and translate the following word combinations.

Physical and chemical changes; Earth’s surface; life forms; to be composed of minerals; common minerals; composition of rocks and minerals; fossil fuels; mineral resources; internal processes; driving forces; volcanic eruptions; stream water; frozen in glaciers; ground water; running water; abundant water; adjacent land; erosion and weathering of continents; mixture of gases; identical in composition; radically different atmospheres; carbon dioxide; surface temperature; atmospheric pressure; inhabited by life; uppermost solid Earth; available sunlight; thin layer; evolution and history of the Earth; evidence preserved in rock and sediment; past life of the Earth.

 

Read the text.

THE SCIENCE OF GEOLOGY

 

Geology is the study of the Earth, including the materials that it is made of, the physical and chemical changes that occur on its surface and in its interior, and the history of the planet and its life forms.

THE EARTHS AND ITS MATERIALS

 

Most of the Earth is composed of rocks. Rock outcrops form some of our planet’s ms spectacular scenery: white chalk cliffs, pink sandstone arches, and the grey granite of Yosemite Valley. Rocks, in turn, are composed of minerals. Although more than 3500 different minerals exist, fewer than a dozen are common. Geologists study the origins, properties, and compositions of both rocks and minerals.

Geologists also explore the Earth for the resources needed in our technological world: fossil fuels such and coal, petroleum, and natural gas; mineral resources such as metals; sand and gravel; and fertilizers. Some search for water in reservoirs beneath Earth’s surface.

 

INTERNAL PROCESSES

 

Processes that originate deep in the Earth’s interior are called internal processes. These are driving forces that raise mountains, cause earthquakes, and produce volcanic eruptions.

 

SURFACE PROCESSES

 

Surface processes are all of those processes that sculpt the Earth’s surface. Most surface processes are driven by water, although wind, ice, and gravity are also significant. The hydrosphere includes water in streams, wetlands, lakes, and oceans, in the atmosphere, and frozen in glaciers. It also includes ground water present in soil and rock to a depth of at least 2 kilometers.

The oceans cover more than 70 percent of our planet. Although oceanography is a separate scientific discipline, it overlaps with geology. Geologic processes form the ocean basins and alter their size and shape. Weathering and erosion of continents carry mud, sand, and salts to the sea. Earth is the only planet in the Solar System that has oceans. It is also the only planet that supports life. Oceanographers examine the oceans’ influence on climate, the atmosphere, life, and the solid Earth.

 

THE ATMOSPHERE

 

The atmosphere is a mixture of gases, mostly nitrogen and oxygen. It is held to the Earth by gravity and thins rapidly with altitude. Ninety-nine percent is concentrated within 30 kilometers of the Earth’s surface, but a few traces remain even 10,000 kilometers above the surface. The interactions among air, rock, and live affect atmospheric composition, temperature, and movement.

 

THE BIOSPHERE

 

The biosphere is the thin zone near the Earth’s surface that is inhabited by life. It includes the uppermost solid Earth, the hydrosphere, and the lower parts of the atmosphere. Land plants grow on the Earth’s surface, with roots penetrating at most a few meters into soil. Animals live on the surface, fly a kilometer or two above it, or burrow a few meters underground. Sea life also concentrates near the ocean surface, where sunlight is available. Some aquatic communities live on the deep sea floor, bacteria live on rock to depths of a few kilometers, and a few windblown microorganisms are found at heights of 10 kilometers or more. But even at these extremes, the biosphere is a very thin layer at the Earth’s surface.

Paleontologists are geologists who study the evolution and history of live by examining fossils and other evidence preserved in rock and sediment. The study of past live shows us that the solid Earth, the atmosphere, the hydrosphere, and the biosphere are all interconnected. Internal processes such as volcanic eruptions and migrating continents have altered the Earth’s climate and atmospheric composition. Life has altered the atmosphere. The atmosphere reacts with rocks.

 

GEOLOGIC TIME

 

During the Middle Ages, the intellectual climate in Europe was ruled by the clergy, who tried to explain natural history by a literal interpretation of the Bible. In the middle 1600s, Archbishop James Ussher calculated the Earth’s age from the Book of Genesis of the Old Testament. He concluded that the moment of creation occurred at noon on October 23, 4004 B.C.

Hutton refuted this biblical logic and deduced that the Earth was infinitely old. Today, geologists estimate that the Earth is about 4.6 years old.

Geologists have divided Earth history into units displayed in the geologic time scale. The units are called eons, eras, periods, and epochs and are identified primarily by the types of life that existed at the various times. The two earliest eons, the Hadean and Archean, cover the first 2.5 billion years of Earth history. Life originated during Archean time. Living organisms then evolved and proliferated during the Proterozoic Eon. However, most Proterozoic organisms had no hard parts such as shells and bones. Most were single celled, although some multicellular organisms existed. The Proterozoic Eon ended about 538 million years ago.

Then within a short time – perhaps 5 million years – many new species evolved. These organisms were biologically more complex that their Proterozoic ancestors, and mane had shells and skeletons. The most recent 13 percent of geologic time, from 538 million years ago to the present, is called the Phanerozoic Eon. The Phanerozoic Eon is subdivided into the Paleozoic Era (“ancient live”), the Mesozoic Era (“middle live”), and the Cenozoic Era (“recent life”).

 

Comprehension check.

1. What does geology study?

2. What processes are called internal and surface ones?

3. What waters does the hydrosphere include?

4. What is ground water? Where in the hydrosphere is it located?

5. What two gases comprise most of the Earth’s atmosphere?

6. How thick is the Earth’s atmosphere?

7. How old is the Earth?

 

Word- building.

a) State to what part of speech the following words belong and translate them into Russian:

science – scientist – scientific – scientifically; geology – geological – geologist; inhabit – inhabitant – inhabitable; mineralogy – mineralogist – mineralogical; develop – development – developed; compose – composer; composition; divide – division – divided; sculpt – sculpture – sculptor; evidence – evident – evidently; occur – occurrence – occurring.

 

Lexical exercises.

a) Give English equivalents of the following:

 

Расстояние; поверхность Земли; выходить на поверхность; происхождение пород; свойства и состав минералов; природный газ; натуральные ресурсы; внутренние и поверхностные процессы; выветривание и эрозия; континенты; климат; геологическая шкала времени; вулканические извержения.

 

b) Read and translate geological terms:

 

Sand; gravel; gravity; ice; rock; stream; land; mud; granite; glacier; eruption; to erupt; soil; earthquake; climate; pressure; weathering; to weather; sediment; sedimentary; arch; terrestrial; metamorphism; metamorphic; igneous; intrusive; extrusive; plutonic; volcanic.

 

P a r t II

Read and translate the following word combinations.

Formation of the Solar System; sequence of events; behavior of dust and gas; observation of stars; matter ejected from a star; the most abundant elements; gravitational attraction; under the influence of gravity; high-speed particles; gravitational collapse; stronger gravitational forces; small rocky spheres; extremely high pressure; nuclear fusion; terrestrial planets; outermost and innermost planets; entire mantle; heavy molten iron.

 

Read the text.

THE EARTH’S ORIGIN

 

THE EARLY SOLAR SYSTEM

 

No one can go back in time to view the formation of the Solar System and the Earth. Therefore, scientists will never be able to describe the sequence of events with certainty.

The hypothesis given here is based on calculations about the behavior of dust and gas in space and on observations of stars and dust clouds in our galaxy.

The hypothesis states that about 5 billion years ago the matter that became our Solar System was an immense, diffuse, frozen cloud of dust and gas rotating slowly in space. This cloud formed from matter ejected from an exploding star. More than 99 percent of the cloud consisted of hydrogen and helium, the most abundant elements in the Universe. The temperature of this cloud was about – 270° C. Small gravitational attractions among the dust and gas particles caused the cloud to condense into a sphere. As condensation continued, the cloud rotated more rapidly, and the sphere spread into a disk. Some scientists have suggested that a nearby star exploded and the shock wave triggered the condensation.

More than 90 percent of the matter in the cloud collapsed toward the center of the disk under the influence of gravity, forming the protosun. Collisions among highspeed particles released heat within this early version of the Sun, but it was not a true star because it did not yet generate energy by nuclear fusion.

Heat from the protosun warmed the inner region of the disk. Then, after the gravitational collapse was nearly complete, the disk cooled. Gases in the outer part of the disk condensed to form small aggregates. Over time, the aggregates stuck together as snowflakes sometimes do. As they increased in size and developed stronger gravitational forces, they attracted additional particles. This growth continued until a number of small rocky spheres, called planetesimals, formed, ranging from a few kilometers to bout 100 km in diameter. The entire process, from the disk to the planetesimals, occurred quickly in geologic terms, over a period of 10,000 to 100,000 years. The planetesimals then coalesced to form a few large planets, including Earth.

At the same time that planets were forming, gravitational attraction pulled the gases in the protosun inward, creating extremely high pressure and temperature. The core became so hot that hydrogen nuclei combined to form the nucleus of the next heavier element, helium, in a process called nuclear fusion. Nuclear fusion releases vast amounts of energy. The onset of nuclear fusion marked the birth of the modern Sun, which still generates its energy by hydrogen fusion.

 

THE MODERN SOLAR SYSTEM

 

Heat from the Sun boiled most of the hydrogen, helium, and other light elements away from the inner Solar System. As a result, the four planets closest to the Sun – Mercury, Venus, Earth, and Mars – are now mainly rocky with metallic centers. These four are called terrestrial planets because they are “Earthlike”. In contrast, the four outer planets – Jupiter, Saturn, Uranus, and Neptune – are called Jovian planets and are composed primarily of liquids and gases with small rocky and metallic cores. Pluto, the outermost known planet, is anomalous. It is the smallest planet in the Solar System and is composed of rock mixed with frozen water and methane.

 

THE EVOLUTION OF THE MODERN EARTH

 

Scientists generally agree that the Earth formed by accretion of small particles. They also agree that the modern Earth is layered. The center is a dense, hot core composed mainly of iron and nickel. A thick mantle, composed mainly of solid rock, surrounds the core and contains 80 percent of the Earth’s volume. The crust is a thin surface veneer, also composed of rock.

Earth temperature and pressure increase gradually with depth.

Although scientists agree that our planer is layered, they disagree on how the layering developed. Astronomers have detected both metallic and rocky meteorites in space, and many think that both metallic and rocky particles coalesced to form the planets. According to one hypothesis, as the Earth began to form, metallic particles initially accumulated to create the metallic core, and then rocky particles collected around the core to form the rocky mantle. Thus, the Earth has always been layered.

An alternative hypothesis states that the rock and metal accumulated simultaneously during the initial coalescence, forming a homogeneous (non-layered) planet. The young Earth became hot as gravity pulled the small particles together and later as asteroids, comets, and planetesimals crashed into the surface. At the same time, radioactive decay heated the Earth’s interior. Thus, our planet became so hot that all or most of it melted soon after it formed. Heavy molten iron and nickel gravitated toward the center and collected to form the core, while lighter materials floated toward the surface to form the mantle. In both hypotheses, the crust formed later.

By studying modern meteorites and lunar rocks, two geologists recently estimated that the core formed at least 62 million years after the Earth coalesced. This interpretation supports the hypothesis that our planet was initially homogenous and then separated into the come and mantle at a later date.

 

Comprehension check.

1. What planets are called terrestrial and Jovian?

2. What are the three major layers of the Earth?

3. What is called planetesimals?

4. How does the Sun still generate its energy?

5. What is the crust composed of?

6. What is the core mainly composed of?

7. What is the outermost layer of the Earth?

 

Word- building.

a) State to what part of speech the following words belong and translate them into Russian:

 

Form – forming – formation; calculate – calculator – calculation; discuss – discussion – discussible; rotate – rotating – rotation; gravity – gravitation – gravitational; add – addition – additional; attract – attracted – attraction; combine – combiner – combination.

 

b) Translate the words paying attention to the suffix – ly:

Primarily; mostly; geologically; originally; entirely; commonly; considerably; gradually; simultaneously; correctly; initially.

 

5. Lexical exercises.

Complete the following sentences:

1. The thin zone near the Earth surface that is inhabited by life is....

2. Paleontologists are geologists who study....

3. Geologists have divided the Earth’s history into units displayed in the.... The units are called....

4. The inner dense hot part of the Earth composed of iron and nickel is the....

5. A thick layer, composed mainly of solid rock, which surrounds the core is..

6. A thin surface veneer composed of rock is the....

 

Summary.

Geology is the study of the Earth including the materials that it is made of, the physical and chemical changes that occur on its surface and in its interior, and the history of the planet and its life forms.

Most of the Earth is composed of rocks, and rocks are composed of minerals. Internal processes move continents and cause earthquakes and volcanoes. Surface processes sculpt mountains and valleys. The hydrosphere consists of water in streams, lakes, and oceans; in the atmosphere; and frozen in glaciers. It also includes ground water that soaks soil and rock to a depth of 2 or 3 kilometers.

The atmosphere is a mixture of gases, mostly nitrogen and oxygen. Ninety-nine percent is concentrated in the first 30 kilometers. Organisms of the biosphere affect Earth’s surface processes and the compositions of the hydrosphere and atmosphere.

The 4.6-billion-year history of the Earth is divided into eons, eras, periods, and epochs.

The Solar System formed from dust and gases that rotated slowly in space.

The modern Earth is made up of a dense core of iron and nickel, a rocky mantle of lower density, and a crust of yet lower density. One hypothesis states that both a core and mantle existed in the earliest Earth. An alternative hypothesis states that the Earth was initially homogenous.

 

Unit II MINERALS

Read the text.

WHAT IS A MINERAL?

 

Comprehension check.

 

1. How many minerals are known to exist in the Earth’s crust?

2. What properties distinguish minerals from other substances?

3. What is an atom? An ion? A cation? An anion?

4. What is a chemical bond?

5. List the rock-forming minerals. Why are they called “rock-forming”? Which are silicates?

6. What is limestone commonly composed of?

7. What is a gem?

 

Word-building.

a) Add the suitable prefixes (in-, im-, ir-, un-, dis-, sub-, pre-, de-, re-) and translate the words:

Appear; location; marine; possible; organic; regular; historic; like; necessary; division; Cambrian; numerable; dependent; usual; construct; compose; stable; terranean.

 

b) Form nouns from adjectives with suffixes –ity, -ance, -ence, -ness, -tion:

Eruptive; thick; existent; important; smooth; similar; destructive; regular; hard; productive; significant; soft; active; dark; constructive; useless; distant.

 

Lexical exercises.

a) Find in the text equivalents of the following:

Неорганическое твердое вещество; синтетический алмаз; органические вещества; существовать самостоятельно; положительный и отрицательный заряды; определенный химический состав; породообразующие минералы; кристаллическая структура; акцессорные минералы; драгоценные и полудрагоценные камни; физические свойства; связь (химическая); соединение.

 

b) Complete the following sentences:

 

1. A naturally occurring inorganic solid with a characteristic chemical composition and a crystalline structure is....

2. A true mineral must form by....

3. Natural gems are valued more highly than....

4. Limestone is commonly composed of the shells of....

5. A positively charged ion is....

6. The forces that hold atoms and ions together to form compounds are called....

7. Substances that make up rocks are called....

 

c) Translate into English:

 

1. Минерал – это залегающее в природе неорганическое твердое вещество с характерным химическим составом и кристаллической структурой.

2. Химический состав и кристаллическая структура – это два самых важных свойства минералов.

3. Органические вещества состоят в основном из углерода.

4. Известняк обычно состоит из раковин мертвых кораллов, моллюсков и других морских организмов.

5. Атом состоит из маленького плотного положительно заряженного ядра.

 

Summary.

 

Minerals are the substances that make up rocks. A mineral is a naturally occurring inorganic solid with a definite chemical composition and a crystalline structure. Each mineral consists of chemical elements bonded together in definite proportions, so that its chemical composition can be given as a chemical formula.

Most common mineral are easily recognized and identified visually.

Although about 3500 minerals are known in the Earth’s crust, only nine rock-forming mineral groups are abundant in most rocks. They are feldspar, quartz, pyroxene, amphibole, mica, the clay minerals, olivine, calcite, and dolomite. The first seven on this list are silicates.

Accessory minerals are commonly found, but in small amounts. Ore minerals, industrial minerals, and gems are important for economic reasons.

 

 

Unit III WEATHERING

P a r t I

Read the text.

WEATHERING

 

Weathering is the decomposition and disintegration of rocks and minerals at the Earth’s surface. Weathering itself involves little or no movement of the decomposed rocks and minerals. This material accumulates where it forms and overlies unweathered bedrock.

Erosion is the removal of weathered rocks and minerals by moving water, wind, glaciers, and gravity. After a rock fragment has been eroded from its place of origin, it may be transported large distances by those same agents: flowing water, wind, ice, and gravity. When the wind or water slows down and loses energy or, in the case of glaciers, when the ice melts, transport stops and sediment is deposited. These four processes – weathering, erosion, transportation, and deposition – work together to modify the Earth’s surface.

 

MECHANICAL AND CHEMICAL WEATHERING

 

The environment at the Earth’s surface is corrosive to most materials. An iron tool left outside will rust. Even stone is vulnerable to corrosion. As a result, ancient stone cities have fallen to ruin. Over longer periods of time, rock outcrops and entire mountain ranges wear away. Weathering occurs by both mechanical and chemical processes. Mechanical weathering reduces solid rock to rubble but does not alter the chemical composition of rocks and minerals. In contrast, chemical weathering occurs when air and water chemically react with rock to alter its composition and mineral content. These chemical changes are analogous to rusting in that the final products differ both physically and chemically from the starting material.

 

MECHANICAL WEATHERING

 

Mechanical weathering breaks large rocks into smaller ones by does not alter the rock’s chemical nature or its minerals.

Five major processes cause mechanical weathering: pressure-release fracturing, frost wedging, abrasion, organic activity, and thermal expansion and contraction. Two additional processes – salt cracking and hydrolysis expansion – result from combinations of mechanical and chemical processes.

 

PRESSURE-RELEASE FRACTURING

 

Many igneous and metamorphic rocks form deep below the Earth’s surface. Over millennia, tectonic forces may raise the pluton to form a mountain range. The overlying rock erodes away as the pluton rises and the pressure on the buried rock decreases. As the pressure diminishes, the rock expands, but because the rock is now cool and brittle, it fractures as it expands. This process is called pressure-release fracturing. Many igneous and metamorphic rocks that formed at depth, but now lie at the Earth’s surface, have been fractured in this manner.

 

FROST WEDGING

 

Water expands when it freezes. If water accumulates in a crack and then freezes, its expansion pushes the rock apart in a process called frost wedging. In a temperate climate, water may freeze at night and thaw during the day. Ice cements the rock together temporarily, but when it melts, the rock fragments may tumble from a steep cliff. In mountains where the daily freeze-thaw cycle occurs, rockfall due to frost wedging is common.

Large piles of loose angular rocks, called talus slopes, lie beneath many cliffs. These rocks fell from the cliffs mainly as a result of frost wedging.

 

ABRASION

 

Many rocks along a stream or beach are rounded and smooth. They have been shaped by collisions with other rocks as they tumbled downstream and with silt and sand carried by moving water. As particles collide, their sharp edges and corners wear away. The mechanical weathering and grinding of rock surfaces by friction and impact is called abrasion. Note that pure water itself is not abrasive; the collisions among rock, sand, and silt cause the weathering.

Wind also hurls sand and other small particle against rocks. Glaciers also cause much abrasion as the drag particles ranging in size from clay to boulders across bedrock. In this case, both the rock fragments embedded in the ice and the bedrock beneath are abraded.

 

ORGANIC ACTIVITY

 

If soil collects in a crack in solid rock, a seed may fall there and sprout. The roots work their way down into the crack, expand, and may eventually push the rock apart. City dwellers often see the results of organic activity in sidewalks, where tree roots push from underneath, raising the concrete and frequently cracking it.

 

THERMAL EXPANSION AND CONTRACION

 

Rocks at the Earth’s are exposed to daily and yearly cycles of heating and cooling. They expand whey they are heated and contract whey they cool. When temperature changes rapidly, the surface of a rock heats or cools faster then its interior and, as a result, the surface expands or contracts faster than the interior, The resulting forces may fracture the rock.

 

Comprehension check.

1. What is the difference among the terms weathering, erosion, transport and deposition?

2. What does the term mechanical weathering imply?

3. List five processes that cause mechanical weathering.

4. How can thermal expansion establish forces that could fracture a rock?

5. Does mechanical weathering alter the chemical composition of minerals?

6. What is called talus slopes? How do they form?

 

Word-building.

Translate the following words:

Contract – contraction – contracted; expand – expansion – expanded; abrade – abraded – abrasion; fluctuate – fluctuated - fluctuation; combine – combined – combination; concentrate – concentrated – concentration; solve – soluble – solution; dissolve – dissolving – dissolved; corrosion – corrosive; effect – effective – effectiveness – effectively; crystal – crystalline – crystallize – crystallization.

 

Lexical exercises.

a) Give English equivalents:

 

механическое и химическое выветривание; разложение (разрушение) пород; движение разрушенных пород; тысячелетие; захороненные породы; неокатанные породы; текущая вода; термальное (тепловое) расширение и сжатие; видоизменять земную поверхность; быть подверженным коррозии; изменять химический состав пород и минералов; отличаться как физически, так и химически от изначального материала; шлифовать породу; на глубине 15 км; давление веса надлежащей породы; чистая (без примесей) вода

 

b) Complete the sentences:

 

1. The decomposition and disintegration of rocks and minerals at the Earth’s surface is....

2. The removal of weathered rocks and minerals by moving water, wind, glaciers, and gravity is....

3. If water accumulates in a crack and then freezes, its expansion pushes the rock apart in a process called....

4. Large piles of loose angular rocks are called....

5. The mechanical wearing and grinding of rock surfaces by friction and impact is called....

 

P a r t II

1. Read and translate the following word combinations.

Common substance; rare in moist environment; hydrogen or hydroxyl ion concentration; acid solution; much more corrosive than pure water; electrically charged hydrogen; bubbles of carbon dioxide gas; slightly acidic; the only rock-forming silicate mineral; unaltered quartz grains; oxidation reaction; acids and bases; solid; liquid; chemical; reversible.

 

Read the text.

CHEMICAL WEATHERING

Rock is durable over a single human lifetime. Over longer expanses of geologic time, however, rocks decompose chemically at the Earth’s surface.

The most important processes of chemical weathering are dissolution, hydrolysis, and oxidation. Water, carbon dioxide, acids and bases, and oxygen are common substances that cause these processes to decompose rocks.

 

DISSOLUTION

 

If you put a crystal of halite (rock salt) in water, in dissolves and the ions disperse to forma solution. Halite dissolves so rapidly and completely that this mineral is rare in moist environment.

A small proportion of water molecules spontaneously dissociate (break apart) to form an equal number of hydrogen ions and hydroxyl ions. Many common chemicals dissociate in water to increase either the hydrogen or the hydroxyl ion concentration. Thus, a solution can become either an acid or a base. Hydrogen and hydroxyl ions are chemically reactive and therefore acids and bases are much more corrosive than pure water.

Water found in nature is never pure. Atmospheric carbon dioxide dissolves in raindrops and reacts to form a weak acid called carbonic acid. As a result, even the purest rainwater, which falls in the Arctic or on remote mountains, is slightly acidic. This acidic rainwater dissolves limestone. Industrial pollution can make rain even more acidic. Limestone outcrops commonly show signs of intense chemical weathering as a result of natural and polluted rain.

In addition, when water flows through the ground, it dissolves ions from soil and bedrock. In some instances, these ions render the water acidic; in other cases the water becomes basic. Flowing water carries the dissolved ions away from the site of weathering. Weathering by solution produces spectacular caverns in limestone.

Most solution reactions are reversible. A reversible reaction can proceed in either direction if conditions change. For example, calcite dissolves readily in acid to form a solution. If a base is added to the solution, solid calcite will precipitate again.

 

HYDROLYSIS

 

During dissolution, a mineral dissolves but does not otherwise react chemically with the solution. However, during hydrolysis, water reacts with a mineral to form a new mineral, with the water incorporated into its crystal structure. Many common minerals weather by hydrolysis. For example, feldspar, the most abundant mineral in the Earth’s crust, weathers by hydrolysis to form clay. As feldspar converts to clay, flowing water carries off soluble cations such as potassium. Tha water combines with the less soluble ions to form clay minerals.

Quartz is the only rock-forming silicate mineral that does not weather to form clay. Quartz resists weathering because it is pure silica, and does not contain any of the more soluble cations.

Because quartz is so tough and resistant to weathering, it is the primary component of sand. Much of it is transported to the sea coast, where it concentrates on beaches and eventually forms sandstone.

 

OXIDATION

 

Many elements react with atmospheric oxygen. Iron rusts when it reacts with water and oxygen. Rusting is one example of a more general process called oxidation. Oxidation reactions are so common in nature that pure metals are rare in the Earth’s crust, and most metallic elements exist in nature as compounds. Only a few metals, such as gold, silver, copper, and platinum commonly occur in their pure states.

Iron is abundant in many minerals, including olivine, pyroxene, and amphibole. If the iron in such a mineral oxidizes, the mineral decomposes. Many metallic elements, such as iron, copper, lead, and zinc, occur as sulfide minerals in ore deposits. When metallic sulfides oxidize, the sulfur reacts to form sulfuric acid, a strong acid. For example, pyrite oxidizes to form sulfuric acid and iron oxide. The sulfuric acid washes into streams and ground water, where it may harm aquatic organisms. This, many natural ore deposits generate sulfuric acid when they weather. The same reaction may be accelerated when ore is dug up and exposed at a mine site.

 

Comprehension check.

 

1. What are the most important processes of chemical weathering?

2. Is water found in nature pure? What makes it acidic?

3. What helps dissolve rocks?

4. What is oxidation? Give an example.

5. What is hydrolysis?

6. Most solution reactions are reversible. What does it mean?

 

Lexical exercises.

a) Match the words and the meanings:

 

intact clean, unmixed

common numerous, plentiful

pure loss, damage

remote simple, ordinary

abundant far, distant

harm hard, strong, firm

tough unbroken, undamaged

durable lasting, existing for a long time

 

b) Find English equivalents in the text:

выветривание; делювиальные склоны; дневной цикл нагревания – охлаждения; морозное расклинивание; гидролиз; окисление; кислотные дождь; декомпрессия (снятие нагрузки (давления) с образованием трещин); механическое (химическое) выветривание; острые края; валун; образование ржавчины

 

Summary.

 

Weathering is the decomposition and disintegration of rocks and minerals at the Earth’s surface. Erosion is the removal of weathered rock or soil by moving water, wind, glaciers, or gravity. After a rock or soil has bee eroded from the immediate environment, it may be transported large distances and deposited.

Unit IV GROUND WATER

Read the text.

Comprehension check.

1. What is permeability?

2. What is porosity?

3. Can soil or rock by porous and not permeable? Permeable but not porous?

4. What is the capillary fringe and how does it form?

5. What is an aquifer and how does water reach it?

6. What is called speleothems?

7. What is karst topography? How can it be recognized?

 

Word-building.

 

a) Give nouns to the following verbs:

 

to appear; to saturate; to exploit; to pollute; to detect; to attract; to connect; to transmit; to accumulate; to aerate; to moisten; to react; to accommodate; to precipitate; to remove; to derive; to add.

 

b) State to what part of speech each word belong and translate them into Russian:

 

axis – axes; astronomy – astronomic – astronomer; crust – crustal; dense – density; entire – entirely; equator – equatorial; explode – explosion; extend – extension – extensive; flat – flatten – flattened; metal – metallic – metalize – metallization; part – partial – partially; press – pressure; sphere – spherical – spheroid; transmit – transmission.

 

Lexical exercise.

 

 

a) Give English equivalents of the following words and expressions;

 

 

грунтовая вода; пористость пород и почвы; проницаемость (фильтрация); пропитывать землю; уровень грунтовых вод; пополнять грунтовые воды; сохранять влажность; создавать формы рельефа (топографию местности); спелеотемы; карстовая воронка.

 

b) Fill in the blanks with the appropriate words:

 

1..... saturates the Earth’s crust in a zone between a few meters and a few kilometers below the surface.

2. In the upper layer of the Earth, bedrock and soil.... small cracks and voids that are filled with air or ground water.

3..... is the ability of rock or soil to transmit water.

4. When rain falls, it usually.... into the ground.

5. The water table is the top of the....

6. Topsoil usually contains abundant.... and.... which retain moisture.

7. During a wet season, rain.... into the ground.... the ground water.

8. Most caverns form at or below....

9. If the roof of a cavern collapses,.... forms on the Earth’s surface.

10. Caverns and sinkholes are common features of....

 

c) Translate into English:

 

1. В верхней части Земли коренная порода и почва содержат маленькие трещины и пустоты, которые заполнены воздухом или грунтовой водой.

2. Несцементированный песок и гравий могут быть как пористыми, так и проницаемыми, т.к. их поры большие и хорошо связаны между собой.

3. Дождевая вода взаимодействует с атмосферным углекислым газом и образует слабо кислый раствор, который может растворять известняк.

4. Высокая влажность пещеры препятствует быстрому испарению воды.

 

Summary.

 

Most of the rain that falls on land seeps into soil and bedrock to become ground water. Ground water saturates the upper few kilometers of soil and bedrock to a level called the water table. Porosity is the proportion of rock or soil that consists of open space. Permeability is the ability of rock or soil to transmit water. An aquifer is a body or rock that can yield economically significant quantities of water. An aquifer is both porous and permeable.

Most ground water move slowly, about 4 centimeters per day. In humid environments, the water table follows the topography of the land.

Caverns form where ground water dissolves limestone. A sinkhole forms when the roof of a limestone cavern collapses. Karst topography, with numerous caves, sinkholes, and subterranean streams, is characteristic of limestone regions.

 

 

Unit V IGNEOUS ROCKS

P a r t I

 

Read the text.

 

Comprehension check.

 

1. What is magma?

2. What processes melt rock to form magma?

3. What are the three main geologic environments in which magma forms in large quantities?

4. What is the temperature of magma?

5. What is the general chemical composition of magmas?

6. Why do magmas begin to rise through the Earth’s outer layers as soon as they form?

7. What factor is the most important in magma production in a subduction zone? What factor is the least important?

8. What rock generally melts at a lower temperature?

9. How is melting caused by decreasing pressure called?

 

Word-building.

 

a) Translate the following words:

 

 

deep – deepen – depth; decrease – decreased – decreasing; melt – melting – molten; prevent – prevention – preventing – prevented; subduct – subduction; solid – solidify – solidification; basalt – basaltic; spread – spreading; chemistry – chemical; divide – division – divided – dividing; inhabit – inhabited – inhabitable

 

b) Translate the following words (mind the prefix –sub):

 

subterranean; subsurface; subsoil; subdivision; subgroup; subcrustal; subtropical; subcontinent; submarine

 

Lexical exercises.

 

a) Translate from Russian into English:

 

магматические породы; повышающаяся температура; падающее давление; добавление воды; тектоническое окружение; точка плавления; сухие породы; тектонический процесс; под океаном; зона субдукции; химический состав; распространенные элементы; относительная пропорция элементов; твердые изверженные породы; центр спрединга; окружающие породы; вулканический остров

 

b) Read and translate geologic terms:

 

crust; magma; mid-oceanic ridge; tectonic plate; rift; mantle plume; buoyant; hot spot; hot spring; subduction; silicon; potassium; sodium; calcite; dolomite

 

c) Translate from Russian into English:

 

1. В определенной среде породы плавятся и образуют магму.

2. Три различных процесса расплавляют астеносферу: повышающаяся температура, понижающееся давление и добавление воды.

3. Добавление воды к породе может расплавить породу.

4. Изверженные породы наиболее многочисленны в горных зонах.

5. Изверженные породы богаты (to be rich in) минералами, которые имеют большое экономическое и научное значение.

 

P a r t II

Read the text.

 

Comprehension check.

 

1. When does an extrusive igneous rock form?

2. When does an intrusive igneous rock form?

3. What factors distinguish obsidian form all other types of igneous rocks?

4. What are the most common minerals in igneous rocks?

5. What is the texture of a rock?

6. What type of igneous rock is the most abundant constituent of continental crust?

7. What rock type makes up most oceanic crust?

 

 

Word-building.

 

 

a) Form negative from the following words using prefixes ir-, im-, un-, dis-, in-, and a suffix –less:

important; regular; appearance; known; useful; count; numerable; possible; rational; changed; common; like; necessary; organic; dependent.

 

b) Form new parts of speech using the suffixes – tion, -ic, - al, - ly, - able, - ity, - fy, - sure, - ture, -ize, -ty:

erupt; mix; create; discuss; active; material; solid; physics; geology; identity; real; concentrate; evaporate; organ.

 

Lexical exercises.

 

a) Complete the sentences:

1. Oxygen and silicon are the two most.... elements in the crust and mantle.

2. When temperature and pressure drop sufficiently, magma.... to form solid igneous rocks.

3. An intrusive igneous rock forms when magma solidifies within....

4. Geologists use both.... and.... to classify and name igneous rocks.

5..... is a volcanic rock intermediate in composition between basalt and granite.

6. Granites are the most.... rocks in continental crust.

7. A granite magma rises through the Earth’s crust and may.... from a volcano to form rhyolite.

 

b) Write out the equivalents in pairs:

 

1. Alter; comprise; total; effect; composition; speed; gravitation; spring.

2. Velocity; change; complete; include; attraction; influence; fountain; structure.

 

c) Translate the sentences into Russian:

 

1.Экструзивные изверженные породы образуются, когда магма извергается и затвердевает на земной поверхности.

2. Интрузивные изверженные породы образуются, когда магма затвердевает внутри коры.

3. Изверженные породы иногда называют плутоническими породами.

4. Два наиболее распространенных типа изверженных пород в земной коре – это гранит и базальт.

 

6. Summary.

 

Geologists separate rocks into three classes based on how they form: igneous rocks, sedimentary rocks, and metamorphic rocks. Igneous rocks form when a hot, molten liquid called magma solidifies.

Three different processes – rising temperature, lowering of pressure, and addition of water – melt portions of the Earth’s asthenosphere. These processes form great quantities of magma in three geologic environments: spreading centers, mantle plumes, and subduction zones. The temperature of magma varies from about 600° to 1400° C. Nearly all magmas are silicate magmas. Magma usually rises toward the Earth’s surface because it is of lower density than rocks that surround it.

An extrusive, or volcanic, igneous rock forms when magma erupts and solidifies on the Earth’s surface. An intrusive, or plutonic, rock forms when magma cools and solidifies below the surface. Plutonic rocks typically have medium- to coarse-grained textures. Volcanic rocks commonly have very fine- to fine-grained textures.

The two most common types of igneous rocks in the Earth’s crust are granite, which comprises most of the continental crust, and basalt, which makes up oceanic crust. The upper mantle is composes of peridotite.

An igneous rock is classified and named according to its texture and mineral composition.

 

Unit VI SEDIMENTARY ROCKS

Read the text.

 

TYPES OF SEDIMENTARY ROCKS

Sedimentary rocks are broadly divided into four categories:

1. Clastic sedimentary rocks are composed of fragments of weathered rocks, called clasts, that have been transported, deposited, and cemented together. Clastic rocks make up more than 85 percent of all sedimentary rocks. This category includes sandstone, siltstone, and shale.

2. Organic sedimentary rocks consist of the remains of plants or animals. Coal is an organic sedimentary rock made up of decomposed and compacted plant remains.

3. Chemical sedimentary rocks form by direct precipitation of minerals from solution. Rock salt, for example, forms when salt precipitates from evaporating sea-water or saline lake water.

4. Bioclastic sedimentary rocks. Most limestone is composed of broken shell fragments. The fragments are clastic, but they form from organic material. As a result, limestone formed in this way is called a bioclastic rock.

 

CLASTIC SEDIMENTARY ROCKS

 

Clastic sediment consists of grains and particles that were eroded from weathered rocks and then were transported and deposited in loose, unconsolidated layers at the Earth’s surface.

Clastic sediment is named according to particle size. Gravel includes all rounded partices larger than 2 millimeters in diameter. Angular particles in the same size range are called rubble. Sand ranges from 1/16 to 2 millimeters in diameter. Silt varies from 1/256 to 1/16 millimeter. Clay is less than 1/256 millimryrt in diameter. Mud is wet silt and clay.

 

TRANSPORT OF CLASTIC SEDIMENT

 

After weathering creates clastic sediment, flowing water, wind, glaciers, and gravite erode it and carry it downslope. Streams carry the gratest proportion of clastic sediment. Because most streams empty into the oceans, most sediment accumulates near continental coastlines. However, some streams deposit their sediment in lakes or in inland basins.

Streams and wind modify sediment as the carry it downslope. The rubble becomes rounded as the stream carries it only a few kilometers. Water and wind round clastic particles as fine as silt by tumbling them against each other during transport. Finer particles do not round as effectively because they are so small and light that water and even wind, to some extent, cushion them as the bounce along, minimizing abrasion. Glaciers do not round clastic particles because the ice prevents the particles from abrading each other.

Weathering breaks bedrock into particles of all sizes, ranging from clay to boulders. Yet most clastic sediment and sedimentary rocks are well sorted – that

is, the grains are of uniform size. Some sandstone formations extend for hundreds of square kilometers and are more than a kilometer thick, but they consist completely of uniformly sized sand grains.

Sorting depends of three factors: the viscosity and velocity of the transporting medium and the durability of the particles. Viscosity is resistance to flow; ice has high viscosity, air has low viscosity, and water is intermediate. Ice does not sort effectively because it transports particles of all sizes, from house-sized boulders to clay.

In contrast, wind transports only sand, silt, and clay and leaves the larger particles behind. Thus, wind sorts particles according to size.

A stream transports only small particles when it flows slowly, but larger particles when it picks up speed, but only small particles during normal flow.

Finally, durability of the particles affects sorting. Sediment becomes abrades as it travels downstream. Thus a stream may transport cobbles form the mountains toward a delta, but the cobbles may never complete the journey because they wear down to smaller grains along the way.

 

LITHIFICATION

 

Lithification refers to processes that convert loose sediment to hard rock. Two of the most important processes are compaction and cementation.

If you fill a container with sand, the sand grains do not fill the entire space. Small voids, called pores, exist between the grains. When sediment is deposited is water, the pores are usually filled with water. The proportion of space occupied by pores depends on particle size, shape, and sorting. Commonly, freshly deposited clastic sediment has about 20 to 40 percent pore space, although a well-sorted and well-rounded sand may have up to 50 percent pore space. Clay-rich mud may have as much as 90 percent pore space occupied by water.

As more sediment accumulates, its weight compacts the buried sediment, decreasing pore space and forcing out some of the water. This process is called compaction. Compaction alone may lithify clay because the platy grains interlock like pieces of a puzzle.

 

TYPES OF CLASTIC ROCKS

 

Water normally circulates through the pore space in buried and compacted sediment. This water commonly contains dissolved calcium carbonate, silica, and iron, which precipitate in the pore spaces and cement the clastic grains together to form a hard rock.

The speed of lithification depends mainly on the availability of cementing material and water to carry the dissolved cement through the sediment.

 

Conglomerate and Breccia

Conglomerate and breccia are coarse-grained clastic rocks. They are the lithified equivalents of gravel and rubble, respectively. In a conglomerate the particles are rounded, and in a sedimentary breccia they are angular.

Gravel typically has large pores between the clasts, because the individual particles are large. These pores usually fill with the finer sediment such as sand or silt. As a result, most conglomerates have fine sediment among the large clasts.

 

Sandstone

Sandstone consists of lithified sand grains. Most sandstones consist predominantly of rounded quartz grains.

The word sandstone refers to any clastic sedimentary rock comprising primarily sand-sized grains. Most sandstones are quartz sandstones and contain more they 90 percent quartz. Arkose is a sandstone comprising 25 percent of more feldspar grains, with most of the remaining grains being quartz. The sand grains in arkose are commonly coarse and angular. Graywacke is a poorly sorted sandsonte with considerable quantities of silt and clay in its pores. Graywacke is commonly dark in color because of fine clay that coats the sand grains. The grains are usually quartz, feldspar, and fragments of volcanic, metamorphic, and sedimentary rock.

 

Claystone, Shale, Mudstone, and Siltstone

Claystone, shale, mudstone, and siltstone are all finegrained clastic rocks. Claystone is composed predominantly of clay minerals and small amounts of quartz and other minerals of clay size. Shale consists of the same material but has a finely layered structure called fissility. Mudstone is a nonfissile rock composed of clay and silt. Siltstone is lithified silt. The main component of most siltsones is quartz, although clays are also commonly present.

Shale, mudstone, and siltstone make up 70 percent of all clastic sedimentary rocks. Shale is usually gray to black due to the presence of partially decayed remains of plants and animals commonly deposited with clay-rich sediment. This organic material in shales is the source of most oil and natural gas.

 

ORGANIC SEDIMENTARY ROCKS

 

Organic sedimentary rocks, such as chert and coal, form by lithification of the remains of plants and animals.

 

Chert

 

Chert is a rock composed of pure silica. It occurs as sedimentary beds interlayered with other sedimentary rocks and as irregularly shaped lumps called nodules in other sedimentary rocks. Chert is made up of the remains of tine marine organisms that make their skeletons of silica rather that calcium carbonate. In contrast, some nodular chert appears to form by precipitation form silica-rich ground water, most often in limestone. Chert was one of the earliest geological resources. Flint, a dark gray to black variety, was frequently used for arrowheads, spear points, scrapers, and other tools chipped to hold a fine edge.

 

Coal

When plants die, their remains usually decompose by reaction with oxygen. However, in warm swamps and in other environments where plant growth is rapid, dead plants accumulate so rapidly that the oxygen is used up long before the dacay process is complete. The undecayed or partially decayed plant remains form peat. As peat is buried and compacted by overlying sediments, it converts to coal, a hard, black, combustible rock.

 

Comprehension check.

 

1. What types of sedimentary rocks do you know?

2. How is clastic sediment named?

3. What is sorting?

4. What factors does sorting depend on?

5. What affects sorting?

6. What is lithification?

7. What does the word sandstone refer to? What does sandstone commonly consist of?

8. What is chert?

9. How does coal form?

 

Word-building.

 

a) Give the verbs corresponding to the following nouns and translate them into Russian:

 

division; erosion; abrasion; conclusion; production; lithification; precipitation; rotation; accumulation; circulation; compaction; evaporation.

 

b) State to what part of speech the following words belong and translate them into Russian:

 

flat – flatten – flattened; rotate – rotation – rotational; constitute – constituent – constitution; transport – transportation – transporting – transported; deposit– deposition – depositional; depend – dependent – dependence – depending – independent – independently; vapor – evaporate – evaporation – evaporating; vary – various – variable – variation – variety; loose – loosen.

 

Lexical exercises.

a) Find in the text equivalents of the following:

 

проточная вода; эродировать разложившуюся породу; большое экономическое значение; главный энергетический источник; состоять из обломков выветренных пород; округленные частицы; впадать в океан; во время транспортировки; разбивать породу на части различных размеров; сопротивление течению; предохранять частицы от абразии; прочность частиц влияет на сортность; состоять из ила и песка; обращать несцементированные осадки в твердую породу; состоять из литифицированных песчаных зерен.

b) Match the words in (1) with the words in (2) and translate the word combinations into Russian:

 

1. Flowing; raw; clastic; sand; plant; loose; hard; dark; flat; microscopic; main.

2. Component; sediment; surface; material; grains; rock; water; remains; examination; in color.

 

Summary.

 

Sedimentary rocks cover about three fourth of the Earth’s land surface.

Clastic sediment is sediment composed of fragments of weathered rock called clasts. Clastic sediment is rounded and sorted during transport and then deposited. Most sediment becomes lithified by compaction and cementation.