Английский язык в сфере профессиональной коммуникации. Геология. Учебное пособие

UNIT 11. ROCK WEATHERING

II. Переведите без словаря:

mechanical action, to operate, atmospheric gases and organisms, effective agents, fragments, position.

III. Прочитайте и переведите текст:

All the materials of the Earth's crust are subjected to cease less change. Under the action of the weather and other agencies even the hardest and most resistant rocks crumble or decay in the course of time. Weathering comprises such agents as mechanical action of temperature changes, freezing of water, rain water, chemical action of the atmospheric gases, water and organisms, whereby rocks at the Earth's surface and near it decay or crumble.

The rate of weathering depends upon the nature of the rocks and the kinds of weathering agents which operate upon them. For example, weathering is much less rapid in the case of hard, resistant rocks, such as granite.

There are two general processes of weathering — one mechanical and the other chemical. In mechanical weathering the rock breaks up or crumbles, with little or no change in the composition of the material. In chemical weathering the composition of the rock is more or less altered during its breaking. These two processes commonly operate together in nature.

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AGENTS OF MECHANICAL WEATHERING

Freezing and thawing of water. Alternate freezing and thawing of water is an effective agency in breaking up rocks. Most relatively hard rocks contain not only many natural fractures called joints, but also microscopic fissures and pores. Surface water may fill such openings. Then this water freezes and expands and exerts a tremendous pressure upon the walls of the fissure. Thus, repeated freezing and thawing of water finally make even the hardest rocks break mechanically into smaller and smaller fragments.

Temperature changes produce expansion and contraction of rocks and minerals. All parts of a rock mass do not expand and contract in equal degree when they are subjected to temperature changes, and so stresses are produced which make the rock break.

When, due to rapid temperature changes surface layers of rocks peel in slabs or sheets, the process is called exfoliation.

Plants and animals both directly and indirectly accomplish considerable work in rock disintegration. Roots of plants insert themselves into rock crevices, and as they grow, they wedge the rock apart. Repetitions of this process often break the rock into small fragments. Burrowing animals, such as earthworms, ants and others aid the action of weathering agents.

Action of rain and wind. Mechanical weathering is accomplished in some measure by the impact of rain drops and by the force of wind, whereby rock fragments are loosened from their positions.

EXERCISES

IV. Образуйте прилагательные от существительных с помощью суффикса — less и переведите их:

1.power — сила;

2.use — польза;

3.cease — остановка;

4.water — вода;

5.end — конец;

V. Найдите эквиваленты английских слов и словосочетаний:

VI. Заполните пропуски соответствующим по смыслу глаголом:

VII. Поставьте вопросы к подчёркнутым членам предложения:

Temperature changes produce expansion and contraction of rocks and minerals.

VIII. Перескажите текст по плану, используя слова, данные в скобках:

1.Ceaseless changes of all the materials of the Earth's crust (to be subjected to).

2.Agents of weathering (temperature changes, freezing of water, rain water, etc.).

3.Rate of weathering (nature of rocks, kinds of weathering agents, to operate).

4.Mechanical and chemical weathering (to crumble, to decay, to alter).

5.Freezing and thawing of water (to fill, joints, fissures, to expand, to exert tremendous pressure).

6.Temperature changes (expansion, contraction, to produce stresses, exfoliation).

7.The work of plants and animals (roots of plants, to insert, to wedge).

8.Action of rain and wind (impact of rain drops, to loosen).

IX. Прочтите текст без словаря и выполните тесты:

Mechanical weathering is due to changes in the temperature of minerals and rocks caused by temperature fluctuations (колебания) of the air and in some cases by direct heat from the Sun. Minerals and rocks expand when they are heated and contract when they are cooled. This expansion and contraction is constantly (постоянно) repeated over a period of hundreds and thousands of years and finally the rock breaks.

Sharp (резкие) temperature changes are observed in spring and in autumn, especially in regions with continental climate, for example, in deserts (пустыни), where the rock surface is heated in the daytime to 700 and cools down to zero at night.

Water helps the action of heat and cold. In rainy weather rocks become wet (влажный) and then dry (cyxoй) again; this repeated wetting and drying breaks the rocks.

Water that freezes in the fine pores and cracks (трещины) of rocks is also of great importance in rock disintegration, because tremendous pressure is exerted by freezing water on the walls of a crack.

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X. Определите какой из заголовков соответствует содержанию прочитанного текста:

1.Chemical weathering.

2.Weathering agents.

3.Mechanical weathering.

XI. Найдите в тексте абзац, в котором есть ответ на вопросы:

a.What is the result of expansion and contraction of minerals and rocks?

b.How does water help the action of heat and cold?

c.In what way does freezing water break rocks?

XII. Кратко перескажите предыдущий текст на английском языке.

XIII. Прочитайте текст и перескажите его на английском языке:

ROCK WEATHERING

All the rocks of the Earth's crust crumble or decay under the action of such agents as mechanical action of temperature changes, freezing of water, rain water, the action of atmosphere, plants and animals, etc.

Minerals and rocks expand when they are heated, and contract when they are cooled. This expansion and contraction of rocks gradually breaks them into smaller fragments.

Freezing and thawing of water that fills fissures and pores of rocks exert a great pressure on the walls of the fissures. By this process rocks break mechanically into smaller fragments. Plants and animals also play an important pant in rock disintegration, as well as rain and wind.

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Carbonation, oxidation and hydration are all very important factors in chemical weathering. They cause increase of volume of the rocks, and the stresses, which develop as a result of volume increase, cause the rocks to crumble.

WORK OF THE ATMOSPHERE

The atmosphere, the outer gaseous envelope of the earth, is an agent of the highest importance in surface geological processes. It not only works directly, in destructive and constructive way, but without it there could be no work from rainfall and running water and the activities of plant and animal life would cease.

In composition air consists of about four parts of nitrogen to one part of oxygen. Although these are the chief elements, there are also carbonic acid gas CO2, in proportion of about 3 volume in 10,000 of air and water vapor whose quantity varies according to temperature, locality and season. There ere also relatively minute amounts of other gases and volatile compounds in the air, but these are not of geological importance.

The destructive work of the atmosphere consists in its chemical action upon rocks and minerals. Due to this action former chemical compounds are broken and new ones are formed in their places. Due to its mechanical activity material driven by the wind is not only transported but abrades and wears away exposed rock surfaces.

The constructive work of the atmosphere is performed by wind which transports and deposits material. Such material may form deposits which are called eolian.

EXERCISES

IV. Образуйте глаголы от данных слов с помощью суффикса -en и переведите их:

1.strength — сила;

2.length — длина;

3.quick — быстрый;

4.thick — толстый;

5.wide — широкий; broad — широкий;

6.deep — глубокий;

V. Найдите в списках А и В синонимы:

VII. Поставьте вопросы к подчёркнутым членам предложения:

1.Carbonic acid gas has the power of chemically uniting with certain minerals and rocks.

2.The atmosphere is the outer gaseous envelope of the Earth.

VIII. Перескажите текст, отвечая на вопросы:

1.What gases considerably increase the solvent power of water?

2.What is the role of carbonation, oxidation and hydration in chemical weathering?

3.What destructive work does the atmosphere perform?

4.What constructive work does the atmosphere perform?

IX. Переведите текст письменно без словаря:

Role of the atmosphere. The chief agent of weathering is the atmosphere which uses energy from the heat of the Sun. Though it is for the most part invisible (не видно), the atmosphere takes part in great changes on the earth.

By carrying moisture (влага) from the sea and precipitating (осаждать) it on the continents the atmosphere makes possible the formation of streams and glaciers, which are powerful eroding agents.

The important geological activities of the atmosphere depend on its peculiar (своеобразный) physical and chemical properties. Since atmosphere is a gas, it penetrates easily into all crevices and other openings that go from the Earth's surface, and so comes into contact with the most part of the bedrock (коренная порода) and the exposed surfaces.

Air distributes heat (распределять), and hence is an important factor in temperature changes that affect rocks near the Earth's surface. About 3/4 of the atmosphere consists of the gas nitrogen, which is rather inert chemically, though with the help of certain plants and bacteria it enters into some important reactions in the ground. Oxygen is much more active chemically and plays a large part in rock weathering.

The geologic role of water vapour is also large, because it moistens (смачивать) the rocks, dissolves some of the minerals directly, takes an essential part in many chemical reactions and helps in mechanical changes.

Other factors of weathering. Temperature changes play a significant part in weathering. They are due to daily and seasonal variations in heat received from the Sun. Plants and animals help directly in breaking rocks, and indirectly but more effectively by producing substances that disintegrate minerals chemically.

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X. Прочитайте текст и кратко передайте его содержание на английском языке:

THE AGENTS OF WEATHERING

The agents of weathering are:

Rain. The destructive effect of rain is both mechanical and chemical but mainly chemical and is strongly influenced by climate.

Frost. Water is a powerful agent in breaking rocks, especially when it freezes in cracks of the rocks.

Wind. The principal effect of the wind is to transport unconsolidated finegrained sediments for considerable distances.

Chemical weathering. The action of vapours and gases in the atmosphere leads to chemical changes in the composition of minerals and rocks. Water vapours may contain in solutions various substances which increase the solubility of minerals.

XI. Переведите текст со словарём:

WEATHERING OF ROCKS

This is the process of decomposition and disintegration of rocks by various agents, the most important of which are percolating water, air, changes of temperature and the action of animals and plants.

PERCOLATING WATER

Percolating water, that is, water which soaks into the soil to bed rock, dissolves some mineral matter from the rocks and changes other minerals. These actions not only remove part of the rock but weaken it so that it is more easily attacked by other weathering agents. The presence in the water of carbon dioxide, which is obtained from the air, increases its solvent power. Stalactites and stalagmites were formed from lime dissolved in percolating water. Percolating water with its dissolved mineral substances ultimately appears as springs, which in turn feed streams, and by them reaches the sea.

AIR

The water vapour and oxygen of the air influence certain minerals in rocks, thus decomposing them. Iron compounds are easily oxidized and broken down in this way, as evidenced by the yellow, red and brownish stains on some rocks. Carbon dioxide obtained from the air increases the weathering power of percolating water. Rocks in arid regions will be little affected.

CHANGES IN THE TEMPERATURE OF THE AIR

Changes in the temperature of the air greatly increase its effectiveness as a weathering agent. The amount of expansion or contraction of any substance differs from that of any other substance when exposed to the same change in temperature. Consequently alternate expansion and contraction of the minerals composing the rock

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through being heated in the daytime and being cooled at night sets up stresses and strains which in time loosen them. They are then more easily affected by percolating water and oxygen, both of which complete the work of weathering. Sometimes the heating and cooling cause thin layers of the rock to break off; this process is known as exfoliation. Changes in temperature are particularly effective as a weathering agent in mountainous and desert regions.

SOLUTION

Chemical Disintegration of Rocks. Water is a solvent for probably all substances that occur in the earths crust although in many cases acting with extreme slowness.

Even rain-water is never pure, but contains salts and gases derived from the air. Principal among them is carbon dioxide, or carbonic acid. Rain-water on reaching the earth flows over the surface or percolates through the soil and rocks, and thus comes into intimate relations with organic acids. The chemical energy of the water is thus greatly increased and becomes an active solvent for most mineral substances. Some of the minerals composing rocks are more soluble than others, and being removed, allow those that remain to crumble and fall apart. The mineral substances taken in solution are, for the most part, carried to streams and by them to the sea, but some water is taken below the surface by percolating waters and undergoes many changes in composition and at the same time produces various alterations in the rocks through which it passes.

The chemical changes produced in the rocks by percolating waters, which is most active near the surface occur also at considerable depths, and there are augmented by the internal heat of the earth. The chemical changes due to percolating water are influenced in variety of ways by temperature. The rocks are dissolved most rapidly in warm, moist regions. Chemical action, in most instances, is retarded by cold; vegetation is less abundant and decays less rapid in cold than in warm climates; it is therefore, in cold regions that the decay of the rocks is at a minimum. In warm, humid countries, deep-rock-decay has usually taken place.

ROCK WEATHERING AND ITS PART IN EROSION

Influence of Rock Composition. Rocks vary greatly in their susceptibility to weathering under different climatic conditions. Quartz is one of the most stable minerals, and rocks composed almost wholly of it, such as quartzite or siliceous sandstone, are especially stubborn in their resistance. Granite decays much more easily in any kind of climate: in a humid region the feldspar decomposes to form clay, and in desert the grains of feldspar and quartz crumble probably through stresses produced by slight hydration of the feldspar. The actual rate at which these changes occur, however, is slow.

Limestone is dissolved wherever there is sufficient water; pores and fissures are formed, and the limestone finally disappears, leaving only a small amount of clay, sand, or other insoluble impurities that may have been contained in it. In a humid climate, therefore, limestones weather faster than many other rock formations and

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tend to form lowlands; but in arid regions extensive solution cannot occur, and there limestone is one of the most resistant kinds of rock. In mane places thick series of limestone layers make up the highest mountain ridges and peaks.

Ordinary shale consists chiefly of clay which was the product of chemical weathering in an earlier geologic period. Further weathering cannot cause much additional change in composition, but shale disintegrates easily into soft clay, especially if it becomes thoroughly soaked with water. In regions of old mountains like the Appalachians, where the rocks are steeply inclined sedimentary strata, the resistant sandstones form high ridges, whereas the weaker shales and limestones underlie the valleys and plains. Some sandstones, however, are not highly resistant. If the grains are cemented with calcium carbonate, solution removes the cementing material and the sand grains crumble.

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