The thickness of crust is not inform rather it differs from place to place by different factors. The crust beneath the ocean is called oceanic crust which has an average thickness of 8 km. The continental crust has an average thickness of 45 km and ranges from 30 km to 70 km. LAYERS OF DIFFERING PHYSICAL PROPERTIES The inner and outer core: Within core a inner region exists where the pressure are so great that the iron is solid despite its high temperature. The solid centre of the earth is the inner core. Surrounding the inner core is a zone where temperature and pressures are so balanced that the iron is molten and exists as liquid.
This is the outer core. The inner core is solid and outer core is liquid. It is believed that the compositions of both are same. The difference is with their physical state. The strength of a solid is controlled by both temperature and pressure. When a solid is heated, it losses strength. When it is compressed, it gains strength. Differences in temperature and pressure divide the mantle and crust into three strength regions. The Mesosphere: In the lower part of the mantle the rock is so highly compressed that it has considerable strength even though the temperature is very high.
Thus a solid egging of high temperature but also relatively high strength exists within the mantle from the core mantle boundary (at 2883 km depth) to a depth of 350 km and is called mesosphere (Middle Sphere). The Stratosphere Within the upper mantle, from 350 to between 100 and 200 km below the earth’s surface , is a region called the stenographer (weak sphere), where the balance between temperature and pressure is such that rocks have little strength. Instead of being strong like the rocks in the mesosphere, rocks in the stenographer are weak and easily deformed, like butter or warm tar.
As far as geologists can tell, the composition of the mesosphere and the stenographer is the same. The difference between them is one of physical properties; in this case the property that changes is strength. The lithosphere Above the stenographer is the outermost strength zone a region where rocks are cooler stronger and more rigid than those in the plastic stenographer. This hard outer region which includes the upper most mantles and all of the crust is called the lithosphere (rock sphere).
It is important to remember that the despite the fact that the crust and mantle fifer in composition it is rock strength not rock composition that differentiates the lithosphere from the stenographer. The difference in strength between rock in the lithosphere and rock in the stenographer is a function of temperature and pressure. At a temperature of 1300. C and the pressure reached at a depth of 100 km, rocks of all kinds’ loose strength and become readily deformable. This is the base of lithosphere beneath the ocean, or, as it is more colloquially termed, the oceanic lithosphere.
The base of the continental lithosphere, by contrast, is about 200 km deep. The reason or the difference Beethoven the two kinds of lithosphere is differing geothermal gradients. Geothermal Gradients: The rate at which temperature increases with depth. It is not constant everywhere in lithosphere. The causes of differences are mostly: thermal properties of rocks differs, volcanism or other heat effects and The thickness of oceanic and continental plates differs. To a first approximation the temperature at the top of the lithosphere is close to O. C.
Because the oceanic lithosphere is about 100 km thick, the average geothermal gradient in the oceanic lithosphere is 1300. C/100 km or 13. C/km. By contrast the continental lithosphere is about 200 km thick, so the average geothermal gradient in the continental lithosphere is about 1350. C/200 km or 6. 7 . C/km. The lithosphere is not a continuous layer; it is broken into number of plates. The earth’s internal convection is always moving the plates of lithosphere and changing the earth’s surface. The continents are drifting sideways at rates up to 12 CM/yr.
The Himalaya is range of a geologically young mountains that began to form when the Indian subcontinent collided with Asia about 45 million years ago. The red sea is a young ocean that started forming about 30 million years ago when a split developed between the Arabian Peninsula and Africa as the two land masses began to move apart. Tectonics is the study of the movement and deformation of lithosphere. Plate Tectonics- the special branch of tectonics that deals with the processes by which place of lithosphere are moved laterally over the stenographer is called plate tectonics. P-28, dynamic earth) HYDROSPHERE This comprises all water resources both surface and ground water. The world’s water is found in oceans and seas, lakes and reservoirs, rivers and treats, glaciers and snowman in the Polar Regions in addition to ground water below the land areas. The distribution of water among these resources is as under Table 1. 1 Table 1. 1 Oceans and Seas 96-97 % Glaciers and polar icecaps 2-3 % Fresh water The water locked up in the Oceans and Seas are too salty and cannot be used directly for human consumption, domestic, agriculture or Industrial purposes.
Only less than 1% of water resources are available for human exploitation. Water is considered to be a common compound with uncommon properties. These uncommon properties (e. G. Anomalous expansion of water) are mainly expansible for supporting terrestrial and aquatic life on earth. BIOSPHERE The biosphere is a capsule encircling the earth’s surface wherein all the living things exist. This portion extends from 10000 m below sea level to 6000 m above sea level. Life forms do not exist outside this zone. The biosphere covers parts of other segments of the environment biz.
Lithosphere, Hydrosphere and Atmosphere. Life sustaining resources like food, water and oxygen present in the biosphere are being withdrawn and waste products in increasing quantities are being dumped. The biosphere has been absorbing this and assimilating them. However the rate of waste dumping has gone beyond the assimilating capability of the biosphere and signals of this stress is becoming evident. ATMOSPHERE It is the gaseous envelope surrounding the earth and extends Upton 500 SMS above the earth’s surface. The composition of the atmosphere is given in Table 1. Constituent Volume % Nitrogen 78. 1 Oxygen 20. 9 Water vapor 0. 1-?5 Argon 0. 9 Carbon dioxide 0. 03 Trace constituents* Balance *The trace constituents include Helium, Neon, Krypton, xenon, SIS, NON, Ammonia, Ozone, and Carbon monoxide etc. The atmosphere, which is a gaseous cover, protects the earth from cosmic additions and provides life sustaining Oxygen, the encountering Nitrogen and Carbon dioxide needed for photosynthesis. The atmosphere screens the dangerous I-XV radiations from the sun and allows only radiations in the range of 300 NM – 2500 NM (near UP to near ‘R) and radio waves.
The atmosphere plays a major role in maintaining the heat balance of the earth by absorbing the re-emitted radiation from the earth. In addition the atmosphere is the medium of carriage of water from the oceans to the land in the hydrological cycle. The Structure of the Atmosphere The atmosphere is broadly divided into four major zones biz. Troposphere, Stratosphere, Mesosphere and Troposphere. Characteristics of these zones are pictorially represented below in Fig. 1. 1 TROPOSPHERE Troposphere is the layer of air nearest to the ground. Temperature decreases with height. The average temperature drops from ICC at sea level to -56. C at 1 1 ,OHO m above sea level. Mixing of the air molecules due to their constant movement (winds) keeps the composition of the gases more or less same throughout the troposphere. An exception to this is water vapor. Most water vapor evaporates from the surface of the Earth and is found in the lower troposphere. Most of the weather occurs in the troposphere. Troposphere is the top of the troposphere, which is a transition layer between Troposphere and Stratosphere. STRATOSPHERE Stratosphere is the layer of air above the troposphere where temperature increases with height.
The average temperature rises to -?2. ICC at 50,000 m above sea level. Ozone is found in higher concentrations between 20 and 30 km above the surface. Hence sometimes this layer is referred to as the “ozone layer”. Ozone absorbs radiant energy from the sun and hence warmer temperatures are encountered in the stratosphere. Stratosphere is the top of he stratosphere, which is a transition layer between Stratosphere and Mesosphere. MESOSPHERE Mesosphere is the layer of air above the stratosphere where temperature decreases with height. The average temperature decreases to -ICC at 90,000 m.
This is the coldest layer of the atmosphere. Masseuse is the top of the mesosphere, which is a transition layer between Mesosphere and Troposphere. TROPOSPHERE Troposphere is the layer of air above the mesosphere. The temperatures in the troposphere increase with increasing height, but there are not many molecules in this layer. The air becomes less and less dense as we reach space. . 2 INTER-RELATIONSHIP BETWEEN THE COMPONENTS AND SUBCOMPONENTS Matters (chemicals) as well as living beings on earth are distributed among the four major Environmental Components biz.
Lithosphere, Hydrosphere, Atmosphere and Biosphere. While for the purpose of studying and understanding the Global Environment this division may be convenient, constant interaction by way of mass and energy transfer between these components and subcomponents is constantly taking place. This is pictorially indicated in Fig. 1. 2 Every sphere has a flow of matter and energy to every other sphere, which is a Ottawa linkage as shown in the figure. Such two-way interactions are also taking place within individual spheres.
This indicates movement of matter/energy from one location to another without exiting the sphere. Environmental problems are hence not confined only to the component/system where they arise but spread to other components as well. A clear example of this is the Acid Rain. Emissions of air pollutants like oxides of Sulfur and Nitrogen are transported over long distances where they are brought down to land and fresh water bodies by rain, creating damage to crops, lands, fresh water resources including ground water, properties and aquatic life.
Another classical example is the buildup of gases like Carbon dioxide in the atmosphere. The emissions may be localized but the impact is massive and global in nature leading to global warming which has far reaching consequences in terms of both area and time. 1. 3 STRUCTURE AND FUNCTIONAL COMPONENTS OF THE ECHO SYSTEM 1. 3. 1 Ecology and Ecosystem The study and understanding of Ecology is an integral part of Environment Science learning. Every living being however small or big depends on the environment for its existence and also competes with others for essentials in life.
For sun. Vial, living beings form groups and different groups compete with each other for survival. The study Of interrelationships between organisms COMPONENTS AND SUBCOMPONENTS OF ENVIRONMENT 7 and group of organisms is called the science of Ecology. The word Ecology has its roots from two Greek words “kiosk” meaning a house or dwelling or place of living or habitat and “logos” meaning study. Ecology is hence the study of interrelationship among plants and animals and their interactions with the physical environment.
Atmosphere Hydrosphere Biosphere Lithosphere Figure 1. 2 There are two important divisions of Ecology. They are : 1) Technology or Species Ecology: This is the study of an individual species. I. E. Behavior, adaptation and interaction of a particular species in its environment. (2) Gynecologist or Ecology of Communities: This is the study of Communities and their interaction with the environment. An Ecosystem is defined as a group of plants, animals or living organisms living together and interacting with the physical environment in which they live.
An Echo system has a more or less a closed boundary and the flow of mass in and out of the system is very less as compared to the internal movement of mass. Ecosystems can be large or small. Examples of large echo systems are rain forests, deserts, salt marshes, coral reefs, lakes and ponds, open ocean, grass lands etc. 1. 3. 2 STRUCTURE AND FUNCTIONAL COMPONENTS OF ECOSYSTEM Any Ecosystem consists of both living (biotic) and nonliving (biotic) components, which are called Environmental or ecological factors. A factor is hence an ecological status, which directly or indirectly affects the life of an organism. PRINCIPLES OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY Biotic Components The physical factors of the environment (which are nonliving) have a major influence on the life of organisms. The biotic components are Of two types. They are : (a) Climatic factors (b) Adapted factors (a) Climatic factors consist of Temperature, rainfall and snow, wind, light, humidity etc. The climate of an area is the result of several factors such as latitude, elevation, nearness to the sea, and monsoon activities and ocean currents.
Temperature influences the rates of biochemical reactions in plants, with the reaction rates approximately doubling with every 1 CO increase. Plant species require a range of temperature to survive. Below a minimum temperature they are inactive, and above a maximum temperature geochemical reactions stop. Normally in many plants growth is possible above ICC. In areas with extremes of temperature, such as the tundra and tropical deserts the plants have mechanisms to adapt to such conditions. Light levels decide the magnitude of photosynthesis reactions.
Different plants have their characteristic light requirements in respect of light intensity, duration and wavelength. Some plants, termed heliports, require high levels, whereas zoophytes can grow in shady, low light conditions. Water is an essential factor for biochemical plant processes, including photosynthesis. Plants growing on lands obtain their water requirements from the soil through their roots by the osmosis process. Plants called Hydrophones grow in fresh water and they cannot withstand drought. Xerography survive long periods of drought, and holography are able to survive in saline water.
Mesosphere require moderate conditions (neither waterlogged nor drought) and are found mainly in temperate areas. (b) Adapted factors or soil factors are pH, mineral and organic matter in soil and texture of soil. Soil is the major source of nutrients and moisture in almost all the land ecosystems. Soil is formed when a rock weathers . The rocks brake down into a collection of different inorganic or mineral particles. The climate influences the type and rate of the weathering of the rocks as well as the nature of the vegetation growing on it.
Nutrients are recycled in the soil by the plants and animals in their life cycles of growth, death and decomposition. Thus humus material essential to soil fertility is produced. Soil mineral matter is derived from the weathering of rock material. These consist of two types biz. Stable primary materials like quartz and various secondary materials like clays and oxides of A and Fee- Soil texture is the efferent size range of mineral particles varying from fine clay to coarse gravel. The varying percentages of each size range produce soils with different characteristics.
Soil organic matter is called humus that is formed by the decomposition of plant and animal matter. The rate of decay depends upon the nature of the material and the climate. The humus produced and incorporated into the soil, is known as clay-humus complexes, which are important soil nutrients. Soil organisms carry out following three main groups of processes. Decomposition of organic material, such as plant and animal parts by cetera, fungi, stationmasters and earthworms.
Bacteria and fungi also breakdown soil mineral matter generating nutrients. Transformation and fixation of Nitrogen (which is an essential plant nutrient) obtained through rainwater or from nitrogen gas in the air. Bacteria like Cabaret and Rhizome in the root nodules of leguminous plants, fix nitrogen from the air. Some types Of bacteria have the ability to transform pesticides and herbicides into less toxic compounds. Structural processes are carried out by domesticates and fungi. Mineral particles are bound together forming larger structures by these organisms.
Earthworms, insects and burrowing mammals, such as moles, assist in the improvement of soil porosity resulting in better aeration and water holding ability. Soil Nutrients are obtained from the weathering of rock material, rainwater, fixing of gases by soil and the decomposition of plant and animal matter. They are available to plants in solution and in clay humus complexes. Soil pH indicates the level acidity or alkalinity of the soil. PH is the concentration of hydrogen ions in the soil. It is measured on a scale from O to 14, with 7 being neutral. A pH value of >7 indicates alkalinity while a value