Complete the sentences with the words from the box. Give a suitable title.

a) composed b) solid c) consists d) land e) inside f) concentric g) compounds h) gaseous  i) rigid  j) molten k) outermost  l) approximately m) inner n) mantle

 

 

The Earth is a … (1) sphere. It is made up of three …(2) spheres or layers. They are known to be the core, the mantle and the crust. The solid sphere is surrounded by a …(3) one, which is known as atmosphere. The scientists know most about the crust of the Earth which is the …(4) sphere. This layer is very thin compared with the core and the mantle. It is only about 10 km thick under the ocean and about 30 km thick on …(5).

The … (6) is much thicker than the crust. It is about 300 km thick. It … (7) mainly of rocks, but we do not know much about their composition. The core, which is situated … (8) the mantle, seems to be divided into two parts. The … (9) core is about 2800 km in diameter. We believe that it is mainly …(10) of iron, but it also contains about 10% of nickel. The layer surrounding the inner core is called the outer core and is …(12) 2000 km thick. It is probably composed of … (11) iron and nickel. These are usually in …(13) called oxides, containing oxygen, or sulphides, containing sulphur. However, the metals in the inner core seem to be … (14), and therefore solid, in spite of the high temperatures at the centre of the Earth.

 

Read the text again and say whether these statements are true or false.

a) The core is spherical in shape.

b) We know more about the composition of the crust than the composition of the mantle.

c) The crust consists of minerals.

d) Iron oxide contains sulphur.

e) The inner core is situated at the centre of the Earth.

f) The outer and the inner cores consist of iron.

g) We know that the inner core is solid while the outer core is liquid.

h) At the center of the Earth, temperature and pressure are both very high.

 

Read the text and give a summary.

The Earth's interior

The Earth's interior is as inaccessible as the most distant galaxies in space. The deepest wells go down only a few kilometers, barely penetrating the surface of our planet. However, geologists have deduced the basic properties of the Earth's interior by studying earthquakes.

Over the centuries, stresses build up in the Earth's crust. Occasionally, these stresses are relieved with a sudden vibra­tory motion called an earthquake. The exact origin of an earthquake, called its focus, is usually deep within the Earth's crust. The point on the Earth's surface directly above the focus is called the earthquake's epicenter.

Earthquakes produce three different kinds of seismic waves that travel around or through the Earth in different ways and at different speeds. Geologists use sensitive seismo­graphs to detect and record these vibratory motions. The rolling motion that people feel near an epicenter is caused by L waves, which travel only over the Earth's surface and are analogous to water-waves on the surface of the ocean. The two remaining kinds of waves, called primary or P waves and secondary or S waves, travel through the Earth. P waves are said to be longitudinal waves because their oscillations are parallel to the direction of wave motion, like a spring that is alternately pushed and pulled. In contrast, S waves are said to be transverse waves because their vibrations are perpendicular to the direction in which the waves are mov­ing. S waves arc analogous to waves produced by a person shaking a rope up and down (P waves travel almost twice as fast as S waves). Consequently, P waves from an earthquake always arrive at a seismographic station be­fore S waves do. By measuring the time delay between the arrivals of these two kinds of waves, geologists can deduce the distance to the earthquake's epicenter.

Seismic waves do not travel along straight lines through the Earth. Because of the varying density and composition of the Earth's interior, both S waves and P waves are bent, or refracted. By studying how these waves are bent, geologists can map out the general structure of the Earth's interior.

When an earthquake occurs in the Earth's crust, seismo­graphs within a few thousand kilometers of the epicenter are able to record both S waves and P waves. However, on the “Opposite” side of the Earth, only P waves can be recorded at seismographic stations. This absence of S waves was first explained in 1906 by the geologist R. D. Oldham, who noted that transverse vibrations such as S waves cannot travel far through liquids. Scientists therefore concluded that our planet has a molten core.

10. Translate into English :

1.Эпицентр землетрясения может быть обнаружен с помощью сейсмографов. 2.Сейсмографы могут также зафиксировать сотрясение Земли в результате взрыва. 3.Таким образом, невозможно взорвать ядерную бомбу или даже запустить ракету, чтобы это оказалось незамеченным на сейсмических станциях по всему миру. 4.Сейсмографы широко используются в геологии. 5. Благодаря им геологи больше не должны сверлить глубокие шахты, чтобы обнаружить залежи минералов. 6. Если мы взорвем динамит в пустой шахте, то передвижной геологический сейсмограф, расположенный неподалеку, сможет записать как изменилась волна при ее прохождении от места взрыва и определить, какие слои расположены на какой глубине. 7. Таким же образом геологи зондируют Землю в местах, где нужно построить плотину или большой промышленный завод.

 

11. It is interesting !

According to National Science Foundation News Paul Butler of the Carnegie Institution in Washington spoke about Gliese 876 – a small, red star with about one-third the mass of the sun that it was the smallest extrasolar planet yet detected and the first of a new class of rocky terrestrial planets. He said that it was like Earth's bigger cousin.

Geoffrey Marcy, professor of astronomy at the University of California, Berkeley, adds: "Over 2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star."

Though the researchers have no direct proof that the new planet is rocky, its mass means it is not a giant gas planet like Jupiter, they said. They estimated the planet's mass as 5.9 to 7.5 times that of Earth. It is orbiting a star called Gliese 876, 15 light years from Earth, with an orbit time of just 1.94 Earth days. They estimated the surface temperature on the new planet to be between 400 degrees and 750 degrees Fahrenheit. Gliese 876 is a small, red star with about one-third the mass of the sun. The researchers said this is the smallest star around which planets have been discovered. In addition to the newly found planet the star has two large gas planets around it.

Butler says the researchers think that the most probable composition of the planet is similar to inner planets of this solar system – a nickel/iron rock. Gregory Laughlin of the Lick Observatory at the University of California, Santa Cruz, says a planet of this mass could have enough gravity to hold onto an atmosphere. "It would still be considered a rocky planet, probably with an iron core and a silicon mantle. It could even have a dense steamy water layer." Three other extrasolar planets believed to be of rocky composition have been reported, but they orbit a pulsar – the flashing corpse of an exploded star – rather than a normal type of star.

GRAMMAR PRACTICE: Functions of Gerund (GR-17, 20, p. 206)

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