BASIC COMPONENTS OF THE ENVIRONMENT

1. BASIC COMPONENTS OF THE ENVIRONMENT

2. The Atmosphere The earth is surrounded by all kind of gases. This layer is called the earth's Atmosphere. Without this atmosphere life on earth isn't possible. It gives us air, water, heat, and protects us against harmful rays of the sun. This layer around the earth is a colourless, odourless, tasteless 'sea' of gases, water and fine dust. The atmosphere is made up of different layers with different qualities. It consists of 78 percent nitrogen, 21 percent oxygen, 0.93 percent argon, 0.03 percent carbon dioxide and 0.04 percent of other gases. The Troposphere is the first layer. Above this layer is the Stratosphere and in between them is the Ozone layer, that absorbs the sun's harmful ultraviolet rays. Above the Stratosphere is the Mesosphere, the Thermosphere including the Ionosphere - and the Exosphere. The atmosphere measures about 500 miles (700km).

3. The atmosphere has no clear boundary at the upper side , because higher the atmosphere, the layer becomes thinner and thinner. It constantly looses molecules of lighter gases such as helium and hydrogen. The further we get from the earth, the atmosphere is divided in thin layers, based on changes in the temperature Troposphere The Troposphere is the lowest layer of the atmosphere and measures about 7 miles(12 km). It contains over 75 percent of all the atmosphere's gases and vast quantities of water and dust. As the sun heats the ground, it keeps this thick mixture churning. The weather is caused by these churnings of the mass. The troposphere is normally warmest at ground level and cools higher up where it reaches its upper boundary (the tropopause). The tropopause varies in height. At the equator it is at 11,2 miles(8 km) high, at 50 N and 50 S, 5,6 miles(9 km) and at the poles 3,7 miles(6 km) high.

4. Stratosphere The Stratosphere extends from the tropopause up to its boundary (the Stratopause), 31 miles(50 km) above the Earth's surface. In this layer there is 19 percent of the atmosphere's gases and it contains little water vapour. Compared to the troposphere it is calm in this layer. The movements of the gases are slow. Within the stratosphere is the ozone layer, a band of ozone gas, that absorbs harmful ultraviolet rays of the sun. The higher you get from the atmosphere, the warmer the air gets. The temperature rises from -76 ºF(-60 ºC) at the bottom to a maximum of about 5 ºF(10 ºC) at the stratopause. Mesosphere The mesosphere is the next layer above the stratopause and extends to its upper boundary (the Mesopause), at 50 miles(80 km) above the ground. The gases in the mesosphere are too thin to absorb much of the sun's heat. Although the air is still thick enough to slow down meteorites hurtling into the atmosphere. They burn up, leaving fiery trails in the night sky. The temperatures in the mesosphere drop to -184ºF (-120ºC) at the mesopause.

5. Layers of the atmosphere The atmosphere is divided into five main layers plus the ionosphere. It extends over 430 miles (700 km) into the Thermosphere: The Thermosphere is the layer above the mesopause. The gases of the thermosphere are even thinner than those in the mesosphere, but they absorb ultraviolet light from the sun. Because of this, the temperatures rise to 3,600 ºF (2,000 ºC) at the top. This is at a height of 430 miles (700 km) of the earth's surface. In the thermosphere is a separate layer, the Ionosphere. This layer extends of 62 miles(100 km) to 190 miles(300 km) of the earth's surface. Ionosphere:The ionosphere is part of the thermosphere. It is made of electrically charged gas particles (ionised). The particles get this electric charge by ultraviolet rays of the sun. The ionosphere has the important quality of bouncing radio signals, transmitted from the earth. That’s why places all over the world can be reached via radio. Exosphere:The Exosphere is the outermost layer of the atmosphere and extends from 430 miles(700 km) to 500 miles(800 km) above the ground. In this layer gases get thinner and thinner and drift off into space.

6. What influence does the Atmosphere have? • The atmosphere is of vital importance for life on earth. Without atmosphere life would be impossible. • It gives us air to breathe and protects us from meteorites and ultraviolet rays from the sun. • The atmosphere absorbs so much heat that temperatures on earth are such that life is possible. • The weather, that exists by constant circulation of water to water vapor, rain to water. • This cycle causes, together with the differences in temperature and circulation of air (wind), erosion of the earth's surface. • By erosion the outside of the earth changes through the years.

7. Lithosphere The lithosphere is the outer solid part of the earth, including the crust and uppermost mantle. The lithosphere is about 100 km thick, although its thickness is age dependent (older lithosphere is thicker). The lithosphere below the crust is brittle enough at some locations to produce earthquakes by faulting, such as within a subducted oceanic plate.

8. Hydrosphere: Almost three-fourth of the earth is covered with water bodies, such as fresh water biomes (lakes, rivers) , marine waters and ice. Estuaries are complex zones of river water mixing with sea. There is a transition zone between terrestrial aquatic systems also. Oceans are rich source of food, minerals energy. Coastal systems are also rich in productivity. Only one percent of water available on the earth is fresh water which is useful to all human activities directly. Earlier civilizations developed near the water bodies also control the climate of a place. Precipitation, runoff, percolation, storage, evaporation, transpiration, humidity and condensation form a water cycle in solid, liquid and vapour stages. Major quantity of water in this natural system is available for use as small portion will be under the process of recycling.

9. Water bodies may be classified as rivers (lotic system) and lakes (lentic system). River water transports and disperses all materials due to continuous flow and mixing. More oxygen is available in the top layers of water. Shallow waters (littoral zone) and open waters (lmnetic zone) will have rooted plants or floating autotrophs(planktons), as plenty of sunshine is available. In the bottom layer of lake,more nutrients(decaying organic matter) may be available, but without sunshine. However, difference in temperature between upper layers (epilimnion) and lower layers (hypolimnion) may cause little vertical mixing even in stagnant lakes. Aquatic life depends upon the following factors: Depth of water and intensity of light penetration. Dissolved oxygen and mineral salts Temperature and solubility Inorganic organic chemicals Bottom deposits and water movement Human activities cause pollution of water bodies,eutophication of lakes, silting of reservoirs,submergence of lands,depletion of water sources and degradation of water quality.

10. Biogeochemical cycles: Biosphere is a bed of resources, activity,utilization and replenishment. Environmental resources are limited asset under a continuous process of material recycling. Microbes,plants and animals play their active role in keeping the essential elements under circulation. Chemical reactions are assisted,accelerated and completed by biological activity. Living systems are unique in their own way. But all the systems are interconnected in many ways in the big universe. The system is self balancing provided the rate of utilization is less than the rate of replenishment and the storage unit is undisturbed.

12. Carbon cycle: The carbon which occurs in organic compounds is included in both the abiotic and biotic parts of the ecosystem. Carbon is a building block of both plant and animal tissues. In the atmosphere, carbon occurs as carbon dioxide (CO2). In the presence of sunlight, plants take up carbon dioxide from the atmosphere through their leaves. The plants combine carbon dioxide with water, which is absorbed by their roots from the soil. In the presence of sunlight they are able to form carbohydrates that contain carbon. This process is known as photosynthesis. Plants use this complex mechanism for their growth and development. In this process, plants release oxygen into the atmosphere on which animals depend for their respiration.

13. Plants therefore help in regulating and monitoring the percentage of oxygen and carbon dioxide in the earth’s atmosphere. All of mankind thus depends on the oxygen generated through this cycle. It also keeps the CO2 at acceptable levels. • Herbivorous animals feed on plant material, which is used by them for energy and for their growth. Both plants and animals release carbon dioxide during respiration. They also return fixed carbon to the soil in the waste they excrete. When plants and animals die they return their carbon to the soil. These processes complete the carbon cycle.

14. Nitrogen Cycle

15. Nitrogen cycle: Carnivorous animals feed on herbivorous animals that live on plants. When animals defecate this waste material is broken down by worms and insects. Mostly beetles and ants. These small “soil animals” break the waste material into smaller bits on which microscopic bacteria and fungi can act. This material is thus broken down further into nutrients that plants can absorb and use for their growth. Thus nutrients are recycled back from animals to plants. Similarly the bodies of dead animals are also broken down into nutrients that are used by the plants for their growth. Thus the nitrogen cycle on which life is dependent is completed. Nitrogen fixing bacteria and fungi in soil gives this important element to plants, which absorb it as nitrates. The nitrates are a part of the plants metabolism, which help in forming new plant proteins.

16. This is used by animals that feed on the plants. The nitrogen is then transferred to carnivorous animals when they feed on the herbivores. Thus our own lives are closely inter- linked to soil animals, fungi and even bacteria in the soil. When we think of food webs, we usually think of the large mammals and other large forms of life. But we need to understand that it is the unseen small animals, plants, and microscopic forms of life. That is of great value for the functioning of the ecosystem.

18. Internal structure of the earth

19. Introduction The earth consists of several layers. The three main layers are the core, the mantle and the crust. The core is the inner part of the earth, the crust is the outer part and between them is the mantle. The earth is surrounded by the atmosphere.

21. The crust covers the mantle and is the earth's hard outer shell, the surface on which we are living. Compared to the other layers the crust is much thinner. It floats upon the softer, denser mantle. The crust is made up of solid material but this material is not the same everywhere. There is an Oceanic crust and a Continental crust. The first one is about 4-7 miles (6-11 km) thick and mainly consists of heavy rocks, like basalt. The Continental crust is thicker than the Oceanic crust, about 19 miles(30 km) thick. It is mainly made up of light material like granite.

22. What does the crust consist of?The crust consists of two parts: the oceanic and the continental crust. Oceanic crust: As the name already suggests, this crust is below the oceans. There, the crust is 4-7 miles (6-11 km) thick. The rocks of the oceanic crust are very young compared with the rocks of the continental crust. The rocks of the oceanic crust are not older than 200 million years. The material of which the oceanic crust consists is for the greater part tholeiitic basalt (this is basalt without olivine). Basalt has a dark, fine and gritty volcanic structure. It is formed out of very liquid lava, which cools off quickly. The grains are so small that they are only visible under a microscope. The average density of the oceanic crust is 3g/cm³.

23. Continental crust: When you look at the globe, you see that the surface of the earth consists of a lot of water (71%). The other 29% consists of land. You can divide this land into six big pieces, which are called continents. The different continents - arranged in decreasing order of size - are: Eurasia (Europe and Asia together), Africa, North-America, South-America, Antarctica and Australia. In the past the division of the continents was different. The earth's crust is the thickest below the continents, with an average of about 20 to 25 miles (30 to 40 km) and with a maximum of 45 miles (70 km). The continental crust is older than the oceanic crust, some rocks are 3.8 billion years old. The continental crust mainly consists of igneous rocks and is divided into two layers. The upper part mainly consists of granite rocks, while the lower part consists of basalt and diorite. Granite is lightly-colored, coarse-grain, magma. Diorite has the same composition, but it's scarcer than granite and is probably formed by impurities in the granite-magma. The average density of the continental crust is 2.7g/cm³.

24. What influence does the crust have? The crust itself has no influence on the earth, but the constant moving of the crust does. This moving is caused by the influence of the convection current, or to be more precise, this convection current actually causes the earth plates to move and sometimes touch each other. These movements cause earthquakes and at weak parts of the earth's crust volcanoes can erupt. Because of all these ongoing movements in the last millions of years, mountains and valleys have been formed, and that’s why the surface of the earth looks as it is now. The form of the surface of the earth has its daily influence on the way people live and work. An example: the building of houses. When you build a house in the mountains, you build it in an other way than on flat land. In the mountains the bottom is more solid than on flat land.Volcanoes and earthquakes also have their direct influence on the people who live near places where they occur. It destroys their houses and many times people are killed or wounded.

25. The Mantle The layer above the core is the mantle. It begins about 6 miles(10 km) below the oceanic crust and about 19 miles (30 km) below the continental crust (see The Crust). The function of the mantle is to separate the inner mantle and the outer mantle. It is about 1,800 miles(2,900 km) thick and makes up nearly 80 percent of the Earth's total volume. Science deals with the structure of the mantle in two different ways. One way is based on its chemical construction (the material), the other on the way layers stream or move.   What does the mantle consist of? Based on the chemical construction: Inner Mantle: the inner mantle can be found between 190 miles (300 km) an 1,800 miles (2,890 km) below the earth’s surface. The average temperature is 5400 ºF (3000ºC), nevertheless the rock is solid because of the high pressures. The inner mantle for the biggest part probably consists of sulphides and oxides of silicon and magnesium. The density is between 4.3g/cm³ and 5.4g/cm³.

26. Outer Mantle: The outer mantle is a lot thinner than the inner mantle. It can be found between 7 miles (10 km) and 190 miles (300 km) below the surface of the earth. You can divide the outer mantle into two different layers. The bottom layer is tough liquid rock and probably consists of silicates of iron and magnesium. The temperature in this part is between 2520°F (1400°C) and 5400°F (3000°C) and the density is between 3.4g/cm³ and 4.3g/cm³. The upper layer of the outer mantle consists of the same material but is stiffer because of its lower temperature. Based on the way layers stream or move: From this perspective, you look at the outer mantle and the crust together. Here we make a difference in asthenosphere and lithosphere. Asthenosphere: The tough liquid part of the outer mantle. Lithosphere: The stiffer part of the outer mantle and the crust. The lithosphere 'floats' on the asthenosphere, like ice on water.

27. What Influence does the Mantle Have? Because the earth is very hot inside, a current of heat flows from the core to the crust. This is called convection current and it also takes place in the mantle. This current cools down as it comes closer to the surface of the earth. As a result, the rising of the current decreases and goes into horizontal direction along the bottom of the crust. When the current cools down more, the convection current descends again and goes to the inner earth. There the temperature increases and the current rises again. This goes on and on. When the current comes at a weaker part of the crust, for example at a volcano, magma comes above the earth's surface. The convection current along the bottom of the crust causes the moving of the tectonic plates. This is called plate tectonics. The movement of these plates goes very slowly. The bumping of two tectonic plates causes an earthquake.

28. The Core The inner part of the earth is the core. This part of the earth is about 1,800 miles (2,900 km) below the earth's surface. The core is a dense ball of the elements iron and nickel. It is divided into two layers, the inner core and the outer core. The inner core - the center of earth - is solid and about 780 miles (1,250 km ) thick. The outer core is so hot that the metal is always molten, but the inner core pressures are so great that it cannot melt, even though temperatures there reach 6700 ° F (3700 ° C). The outer core is about 1,370 miles (2,200 km) thick. Because the earth rotates, the outer core spins around the inner core and that causes the earth's magnetism.

29. What does the core consist of? Inner core: It is 3,200 - 3,960 miles (5,150-6,370 km) below the earth's surface and mainly consists of iron, nickel and some lighter elements (probably sulphur, carbon, oxygen, silicon and potassium. The temperature in the inner core is about 9032 - 10832°F(5000-6000°C). Because of the high pressure, the core is solid. The average density of the core is about 15g/cm³. Outer core: The outer core is at 1,800 - 3,200 miles (2,890-5,150 km) below the earth's surface. The outer core is liquid and mainly consists of iron, some nickel and about 10% sulphur and oxygen. The temperature in the outer core is about 7200 - 9032°F (4000-5000°C ). The density of the outer core is between the 10g/cm³ and 12,3g/cm³. The outer core and inner core together cause the earth's magnetism.

30. What Influence does the Core have? Because the core is so hot, it radiates a natural heat to the upper layers. Because of this a current of heat comes into being. Those are also known as the convection currents. The convection currents cause the movement of the tectonic plates. This movement is called plate tectonics. The outer core and the inner core together cause the earth's magnetism. Because the earth rotates, the outer core spins, the inner core doesn't spin because it's solid. This gives a kind of dynamo effect and causes the earth's magnetism. Magnetism has been used by sailors to find their way on earth for thousands and thousands of years. Magnetism also influences electro-particles outside the atmosphere of the earth, up to more than 37,000 miles (60,000 km) into space.