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§ 17. Earth structure (textbook)

§ 17. Internal Earth structure


Now scientists know about Earth structure less than, say, the space surrounding our planet. Penetrate into the subsoil can only "On the wings of science". What lies at our feet, stubbornly maintains its secret. Scientists suggest that the Earth consists of three main parts: core, mantle and crust.

Fig. Earth structure


Kernel. Core - a central, medullary part globe. It still is a mystery to science. Confidently can say only its range - about 3500 km. Scientists believe that the outer part of the kernel is in the molten-liquid state, and internal - in the solid. Admitting also that the core consists of a substance similar to metals (iron, whether silicon or iron and nickel, there are other assumptions). The temperature in the core reaches 50000 С.

Mantle. This - the lining that covers the nucleus (from the Greek "mantle" - "veil"). Its capacity of nearly 3 000 km. Mantle - The largest planet of the inner membranes (83% of the Earth). Mantle as core, no one has ever seen. Admitting that the closer to the center of the Earth, the There is greater pressure and higher temperature: from a few hundred degrees to  2 500 0C. At this temperature mantle substance would be molten, but prevents a lot of pressure melting. Therefore we think that it hard, but at the same time and heated.

Scientists suggest that the upper mantle composed solid ground, ie it hard. But it at a depth of 50-250 km from the Earth's surface is placed partially molten layer - Asthenosphere. It is relatively soft and plastic as plasticine or wax. This substance can slow mantle flow and thus move. Speed of movement is very small - a few centimeters per year. However, it plays a crucial role in the movements of the earth's crust, about be discussed further.

Terrestrial bark. Crust - the outer hard layer of our planet. Compared to the core and mantle, it is very thin. Thickness (thickness) crust largest in the mountains - 70 km, under the plains it is 35-40 km, and under the ocean - only 5-10 km. Earth crust is often compared apples with skin as opposed to all his flesh. However, this is the earth crust, which is the basis for the people of the world. It is at This thin crust built the city on it go people, flowing river, reduction are the sea and oceans of it mined minerals.

Drop in deep into the crust to help mine and well set up to mining operations. People have long noticed that the increase in mines depth the temperature rises. For example, at a depth of 1000 m miners working under heat (about 30 0C). Heat is transferred from the earth's crust mantle. From the scientific purpose geologists drill ultradeep wells. The deepest of these (15 km) drilled in Russia Kola Peninsula. With such narrow holes get samples of matter and investigate it thoroughly.

Best Earth crust surface is known in part on land. It is seen in outcrops on the mountain slopes, steep banks of rivers, quarries. On the surface layer Earth's crust affect the sun. In summer it gets warm, autumn cooled, freeze in winter, and spring roztaye and gradually again hot. However, already at a depth of 20-30 meters, regardless of seasons, temperature held the same year round. And then it begins with the depth increase.

Crust with the upper mantle form shell - lithosphere. It is the only hard (stone) layer, which floats in like a plastic Asthenosphere. Lithosphere thickness varies: under the ocean - about 50 km on the continents - 200 km.

From the Earth structure involves a lot questions of importance to  people. Why earthquakes occur and how they zavbachuvaty? Is moving continents? Is enough minerals and where to look? Apparently, there are many secrets, the key to which lies deep in the bowels of the planet. Their knowledge will allow to read stone chronicle of the Earth. In it - information about the substance and energy of the earth's depths.

Composition, structure and history of Earth science studies geology.


Questions and Tasks

1. What has the internal structure of the Earth?

2. What you know about the core of our planet?

3. Tell us about the Earth's mantle.

4. Show on map hemisphere where the Earth's crust may have the greatest capacity and where - the smallest.

5. What is the lithosphere?

6. Why scientists are trying to penetrate the depths of the earth?