5)…Английский для Горных Инженеров

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Unit_4_ТЕКСТ А Sedimentary Rocks

The rocks of the Earth's crust are divided into three main groups: sedimentary rocks, which consist of fragments or particles of pre-existing rocks; igneous rocks which have solidified from magma and metamorphic rocks. Metamorphic rocks have been de­rived from either igneous or sedimentary rocks.

Sedimentary rocks represent one of the three major groups of rocks that make up the crust of the Earth Most sedimentary rods have origi­nated by sedimentation. They are layered or stratified. Thus, statification is the most important characteristic of sediments and sedimentary rocks. It is necessary to note that the processes which lead to the formation of sedimentary rocks are going on around us.

Sediments are formed at or very near the surface of the Earth by the action of heat, water (rivers, glaciers, seas and lakes) and organisms.

Fig. 1 shows relative abundance of sedimentary rocks and igne­ous rocks. It should be noted that 95 per cent of the Earth's crust is made up of igneous rocks (see Fig. 1 left) and that only 5 per cent is sedimentary. 11n contrast, the amount of sedimentary rocks on the Earth's surface is three times that of igneous rocks (see Fig. 1 right)-:

Strictly speaking, sedimentary rocks form a very small proportion by volume of the rocks of the Earth's crust. On the contrary, about three quarters of the Earth's surface is occupied by sedimentary rocks. It means that most of sedimentary rocks are formed by sediments, accumulations of solid material on the Earth's surface.

Осадочные породы

Скалы Земной коры разделены на три главных группы: осадочные породы, которые состоят из фрагментов или частиц существующих ранее скал; магматические породы, которые укрепились от магмы и метаморфических пород. Метаморфические породы были получены или из магматических или из осадочных пород.

Осадочные породы представляют одну из трех главных групп скал, которые составляют корку Земли, которую Большинство осадочных прутов породило отложением осадка. Они выложены слоями или стратифицированы. Таким образом statification является самой важной особенностью отложений и осадочных пород. Необходимо отметить, что процессы, которые приводят к формированию осадочных пород, продолжаются вокруг нас.

Отложения сформированы в или очень около поверхности Земли тепловым воздействием, вода (реки, ледники, моря и озера) и организмы.

Рис. 1 показывает относительное изобилие осадочных пород и магматических пород. Нужно отметить, что 95 процентов Земной коры составлены из магматических пород (см., что Рис. 1 уехал), и что только 5 процентов являются осадочными. 11n контраст, количество осадочных пород на поверхности Земли в три раза больше чем это магматических пород (см. право Рис. 1)-:

Строго говоря осадочные породы формируют очень маленькую пропорцию объемом скал Земной коры. Напротив, приблизительно три четверти поверхности Земли занят осадочными породами. Это означает, что большинство осадочных пород сформировано отложениями, накоплениями твердого материала по поверхности Земли.

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Unit_4_ТЕКСТ Б Weathering of Rocks

All rocks which are exposed on the Earth's surface (high moun­tain peaks, deserts) are decomposed to a certain degree. The process of rock disintegration by the direct influence of local atmospheric conditions on the Earth's surface is called weathering. This phenomenon is often referred to in geology because weathering is an active process. It takes place in the upper layers of the Earth's crust.

The main cause of physical weathering is the change in tempera­ture that takes place with the succession of day and night. This phenomenon can best be observed in the deserts and high moun­tains where the changes in temperature are common.

During the day under the influence of heat, rocks expand whereas at night they begin to contract. As rocks are generally com­posed of different minerals, their expansion and contraction do not occur uniformly. As a result of this rocks crack. At the beginning these cracks or fissures are hardly noticeable but gradually they become wider and deeper until the whole surface of rock is finally transformed into gravel, sand or dust.

In the regions of a moderate or cold climate, where the tem­perature in winter goes down to below 0 (zero), the decomposition of rocks is greatly facilitated by the action of water. When water freezes it increases in volume and develops enormous lateral pressure. Under the action of water, rocks decompose to pieces of varied forms and sizes.

The decomposition of rocks under the direct influence of heat and cold is called physical weathering.

Rocks are subjected not only to physical decomposition but also to chemical weathering, i.e. to the action of chemical agents, such as water, carbon dioxide and oxygen. In a general way, chemical weathering is an acid attack on the rocks of the Earth's crust, in particular an attack on the most abundant minerals — quartz (sand) and aluminosilicates (clays). Only few minerals and rocks are resistant to the action of natural waters. The solvent action of water is stronger when it contains carbon dioxide. Water causes more complex and varied changes. With the participation of oxygen and carbon dioxide up to 90 per cent of rocks is transformed into soluble minerals, which are carried away by the waters.

Organisms and plants also take part in the disintegration of rocks. Certain marine organisms accelerate the destruction of rocks by making holes in them to live in. The action of plants can often be even more destructive. Their roots penetrate into the fissures of rocks and develop the lateral pressure which fractures and destroys rocks