Is ground solid enough to stand on. Authors: Virginia Evans, Ksenia Baranova/ 11B

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Teacher: R. I. Nikolaeva. Form 11 ‘B’. The Unit №2.14. Student's Book ‘Starlight’ 11. (Authors: Virginia Evans, Ksenia Baranova) The Theme of the unit: ‘Is ground solid enough to stand on?‘ The aim of the unit: Curricular cut. Form of work: Work in groups. 1) Collecting information about Earth's plates 2) Making Projects on the topic. 3) Presentation Projects to the class. The material used: Internet, technical literature, Student's Book.

Transcript of Is ground solid enough to stand on. Authors: Virginia Evans, Ksenia Baranova/ 11B

Page 1: Is ground solid enough to stand on. Authors: Virginia Evans, Ksenia Baranova/ 11B

Teacher: R. I. Nikolaeva.Form 11 ‘B’.

The Unit №2.14. Student's Book ‘Starlight’ 11.

(Authors: Virginia Evans, Ksenia Baranova)

The Theme of the unit:

‘Is ground solid enough to stand on?‘

The aim of the unit:

Curricular cut. Form of work:

Work in groups.

1) Collecting information about Earth's plates 2) Making Projects on the topic. 3) Presentation Projects to the class. 

The material used: Internet, technical literature, Student's Book.

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Inner core

The inner core of the Earth, its innermost part, is a primarily solid ball with a radius of about 1,220 km (760 mi), according to seismological studies. This is about 70% of the Moon's radius.) It is believed to consist primarily of an iron-nickel alloy, and to be approximately the same temperature as the surface of the Sun: approximately 5430 °C.

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Discovery

The Earth was discovered to have a solid inner core distinct from its liquid outer core in 1936, by the seismologist Inge Lehmann who deduced its presence from observations of earthquake-generated seismic waves that reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth's surface. This boundary is known as the Bullen discontinuity, or sometimes as the Lehmann discontinuity. A few years later, in 1940, it was hypothesized that this inner core was made of solid iron; its rigidity was confirmed in 1971.

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The outer core was determined to be liquid from observations showing that compressional waves pass through it, but elastic shear waves do not - or do so only very weakly. The solidity of the inner core had been difficult to establish because the elastic shear waves that are expected to pass through a solid mass are very weak and difficult for seismographs on the Earth's surface to detect, since they become so attenuated on their way from the inner core to the surface by their passage through the liquid outer core. Dziewonski and Gilbert established that measurements of normal modes of vibration of Earth caused by large earthquakes were consistent with a liquid outer core. Recent claims that shear waves have been detected passing through the inner core were initially controversial, but are now gaining acceptance

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Composition

Based on the relative prevalence of various chemical elements in our solar system, the theory of planetary formation, and constraints imposed or implied by the chemistry of the rest of the Earth's volume, the inner core is believed to consist primarily of a nickel-iron alloy known as NiFei 'Ni' for nickel, and 'Fe* for ferrum orion. The core also contains enough gold, platinum and other siderophile elements, which would cover the entire Earth with a coating 0.45 m deep. Core's temperature is about 5,700 К (5,430 °C; 9,800 °F). The pressure in the Earth's inner core is slightly higher than it is at the boundary between the outer and inner cores: it ranges from about 330 to 360 gigapascals.

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Temperature and pressure

The temperature of the inner core can be estimated by considering both the theoretical and the experimentally demonstrated constraints on the melting temperature of impure iron at the pressure which iron is under at the boundary of the inner core (about 330 GPa). These considerations suggest that its temperature is about 5,700 K.

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The crust

In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. The crusts of Earth, the Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles.

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Earth's crust and mantle

The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust.

The crust occupies less than 1% of Earth's volume.[l] The oceanic crust of the sheet is different from its continental crust. The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick[2] and is composed primarily of basalt, diabase, and gabbro. The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick and is mostly composed of slightly less dense rocks than those of the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust. Both the continental and oceanic crust "float" on the mantle. Because the continental crust is thicker, it extends both above and below the oceanic crust. The slightly lighter density of felsic continental rock compared to basaltic ocean rock contributes to the higher relative elevation of the top of the continental crust. Because the top of the continental crust is above that of the oceanic, water runs off the continents and collects above the oceanic crust. The continental crust and the oceanic crust arc sometimes called sial and sima respectively. Because of the change in velocity of seismic waves it is believed that on continents at a certain depth sial becomes close in its physical properties to sima, and the dividing line is called the Conrad discontinuity.

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Composition

The continental crust has an average composition similar to that of andcsite. Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle. Although the continental crust comprises only about 0.6 weight percent of the silicate on Earth, it contains 20% to 70% of the incompatible elements.

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Lithosphere is the hard shell of the Earth, which includes the crust and part of the upper mantle. Lithosphere thickness on land generally varies from 35-40 km (in the plains) to 70 km (in mountainous areas). There's even more crustal thickness under the ancient mountains: for example, under the Himalayas its power reaches 90 km. The earth's crust under the oceans - is also the lithosphere. Here she is fine - an average of about 7-10 km, and in some areas of the Pacific Ocean - to 5 km.

The thickness of the crust can be determined by the propagation velocity of seismic waves. The latter also give some information about the properties of the mantle beneath the crust and a member of the lithosphere. Lithosphere, as well as hydrosphere and atmosphere was formed primarily as a result of the release of substances from the upper mantle of the young Earth. Its formation is still going on, mainly on the ocean floor.

Most of the lithosphere constitutes crystalline substances, which were formed during the cooling of magma - molten material in the Earth's depths. Hot solutions were formed during the cooling of magma too. They were cooled and recovered substances contained, passing through the cracks in the earth's crust. Since some of the minerals and the temperature change of pressure decay on the surface are converted into new compounds.

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Lithosphere is exposed to air and water layers of the Earth (atmosphere and hydrosphere), resulting in weathering processes. Physical weathering is a mechanical process, in which rock is crushed to a smaller particle size, without changing the chemical composition. Chemical weathering results in the formation of new substances. Biosphere, as well as land topography and climate, affects the rate of weathering, water composition and other factors.

Unconsolidated continental deposits, the power of which is ranging from 10-20 cm on the steep slopes of up to tens of meters on the plains and hundreds of meters in the valleys, were formed by weathering. Soils , which play an important role in the interaction of living organisms with the crust, were formed on these deposits.

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An atmosphere is a layer of gases surrounding a planet that is held in place by the gravity. An atmosphere is more likely to be retained if the gravity is high and the atmosphere's temperature is low. Earth's atmosphere, which contains oxygen used by most organisms for respiration and carbon dioxide used by plants, and bacteria for photosynthesis, also protects living organisms from genetic damage by solar ultraviolet radiation. Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.

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The atmosphere of the Earth may be divided into several distinct layers. The troposphere is where all weather takes place; it is the region of rising and falling packets of air. Above the troposphere is the stratosphere, where air flow is mostly horizontal. The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun.

Above the stratosphere is the mesosphere and above that is the ionosphere (or thermosphere), where many atoms are ionized (they have gained or lost electrons so they have a net electrical charge). The ionosphere is very thin, but it is where aurora take place, and is also responsible for absorbing the most energetic photons from the Sun, and for reflecting radio waves, thereby making long-distance radio communication possible.

The Earth's atmosphere is about 480 km thick, but most of the atmosphere (about 80%) is within 16 km of the surface of the Earth. There is no exact place where the atmosphere ends; it just gets thinner and thinner, until it merges with outer space.

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The hydrosphere - the water cover of Earth including oceans, the seas, the rivers, lakes, underground waters and glaciers, a snow cover, and also water vapor in the atmosphere. Earth hydrosphere for 94% is presented by salty waters of oceans and the seas, more than 75% of all fresh water are preserved in polar caps of the Arctic and Antarctica.

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Water on Earth is present at all three aggregate states, however its greatest volume is the share of a liquid phase which is very significant for formation of other features of a planet. All natural water complex functions as a unit, being in a condition of continuous movement, development and updating. The surface of the World Ocean occupying about 71% for a terrestrial surface, is located between the atmosphere and a lithosphere. Earth diameter, i.e. its equatorial diameter, makes 12 760 km, and the average depth of the ocean in its modern bed - 3,7 km. Therefore, thickness of a sheet of water in a liquid state averages only 0,03% of terrestrial diameter. In effect, it is the thinnest water film on Earth surface, but, as the ozone protective layer, playing an extremely important role in biospheric svstem.

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Without water there couldn't be a person, an animal and flora as the majority of plants and animals consists generally of water. Besides, temperatures are necessary for life in the range from 0 to 100 °C that corresponds to temperature limits of a liquid phase of water. For many living beings water serves as habitat. Thus, the main feature of the hydrosphere is abundance of life in it.

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The hydrosphere role in maintenance of rather invariable climate on a planet as she, on the one hand, acts as heat accumulator is great, providing constancy of average planetary temperature of the atmosphere, and with another -at the expense of a phytoplankton produces nearly a half of all oxygen of the atmosphere.

The water environment is used for fishing of fish and other seafood, collecting plants, production of underwater deposits of ore (manganese, nickel, cobalt) and oil, transportation of goods and passengers. In production and economic activity of people applies water to cleaning, washing, cooling of the equipment and materials, watering of plants, hydrotransportation, ensuring specific processes, for example electric power developments, etc.

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The important circumstance inherent in the water environment, that infectious diseases (about 80% of all diseases) are generally transmitted through it is. Simplicity of process of flooding in comparison with other types of burial, inaccessibility of depths to the person and seeming isolation of water led to that the mankind actively uses the water environment for dumping of production wastes and consumption. Intensive anthropogenous pollution of the hydrosphere conducts to serious changes of its geophysical parameters, ruins water ecosystems and it potentially danserous to the person.

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Ecological threat to the hydrosphere set the task of acceptance of urgent measures of rescue of habitat of mankind for the international community. Their feature is that any state separately even by means of strict measures isn't capable to cope with ecological threat. Therefore the international cooperation in this area, acceptance of the optimum ecological strategy including the concept and the program of joint actions of all countries is necessary.