Unit 1
Composition of Earth Crust
Earth Layers
The Earth is divided into four main layers
- Inner Core
- Outer Core
- Mantle
- Crust
The Earth’s Crust
The crust is the thinnest layer on Earth, 5 km to 100 km
There are two types of crust
- Oceanic crust – made mostly of the igneous rock basalt. Found under the ocean. Relatively thin, 5 km to 7 km. Contains more iron than the Continental crust, therefore is more dense.
- Continental crust – made mostly of granite. Found under the continents. Relatively thick, up to 100 km.
Special parts of the Crust
Lithosphere
- Crust is the upper part of the lithosphere.
- Broken up into large plates. •
- The uppermost part of the mantle is also part of the Lithosphere
Asthenosphere
- Upper part of mantle, below lithosphere
- 130 – 160 km thick
- Cooler part of the mantle that the lithosphere plates slide on top of.
The Earth’s Mantle
- Located directly above the outer core
- Starts below the crust
- Is the largest layer
- 80% of the Earth’s volume & 68% of Earth’s mass
The Earth’s Mantle
- Composed of more iron than the crust.
- Density, pressure, and temperature all increase the deeper you go in the mantle
Composition of the Earth
- Scientists cannot see the interior of the planet, or drill to the core, so they use seismic waves to determine the composition of the layers.
- Seismic waves: are vibrations that are produced when an earthquake happens.
- Seismic waves travel at different speed depending on the composition and density of material.
Composition of Atmosphere
The atmosphere is composed of gases, water vapour and dust particles. Table 8.1 shows details of various gases in the air, particularly in the lower atmosphere. The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.
Composition of Atmosphere Permanent Gases of the Atmosphere Constituent % by Volume
- Nitrogen (N2) 78.08
- Oxygen (O2) 20.95
- Argon (Ar) 0.93
- Carbon dioxide (CO2) 0.0325
- Neon (Ne) 0.002
Gases
Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the green house effect. The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels. This has also increased the temperature of the air. Ozone is another important component of the atmosphere found between 10 and 50 km above the earth’s surface and acts as a filter and absorbs the ultra-violet rays radiating from the sun and prevents them from reaching the surface of the earth.
Water Vapour
Water vapour is also a variable gas in the atmosphere, which decreases with altitude. In the warm and wet tropics, it may account for four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air. Water vapour also decreases from the equator towards the poles. It also absorbs parts of the insolation from the sun and preserves the earth’s radiated heat. It thus, acts like a blanket allowing the earth neither to become too cold nor too hot. Water vapour also contributes to the stability and instability in the air.
Dust Particles
Atmosphere has a sufficient capacity to keep small solid particles, which may originate from different sources and include sea salts, fine soil, smoke- soot, ash, pollen, dust and disintegrated particles of meteors. Dust particles are generally concentrated in the lower layers of the atmosphere; yet, convectional air currents may transport them to great heights. The higher concentration of dust particles is found in subtropical and temperate regions due to dry winds in comparison to equatorial and polar regions. Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.
1. Troposphere
- TROPOSPHERE
This is the layer of the atmosphere closest to the Earth's surface, extending up to about 10-15 km above the Earth's surface. It contains 75% of the atmosphere's mass. The troposphere is wider at the equator than at the poles. Temperature and pressure drops as you go higher up the troposphere. The Tropopause: At the very top of the troposphere is the tropopause where the temperature reaches a (stable) minimum. Some scientists call the tropopause a "cold trap" because this is a point where rising water vapor cannot go higher because it changes into ice and is trapped. If there is no cold trap, Earth would lose all its water! The uneven heating of the regions of the troposphere by the Sun causes convection currents and winds. Warm air from Earth's surface rises and cold air above it rushes in to replace it
- TROPOPAUSE
The zone separating the tropsophere from stratosphere is known as the tropopause. The air temperature at the tropopause is about minus 800C over the equator and about minus 45o C over the poles. The temperature here is nearly constant, and hence, it is called the tropopause.
2. Stratosphere
- STRATOSPHERE
This layer lies directly above the troposphere and is about 35 km deep. It extends from about 15 to 50 km above the Earth's surface. The lower portion of the stratosphere has a nearly constant temperature with height but in the upper portion the temperature increases with altitude because of absorption of sunlight by ozone. This temperature increase with altitude is the opposite of the situation in the troposphere.
The Ozone Layer The stratosphere contains a thin layer of ozone which absorbs most of the harmful ultraviolet radiation from the Sun. The ozone layer is being depleted, and is getting thinner over Europe, Asia, North American and Antarctica --- "holes" are appearing in the ozone layer.
- STATOPAUSE
The stratopause (formerly Mesopeak) is the level of the atmosphere which is the boundary between two layers: the stratosphere and the mesosphere. In the stratosphere the temperature increases with altitude, and the stratopause is the region where a maximum in the temperature occurs.
3. Mesosphere
- Mesosphere
The mesosphere lies above the stratosphere, which extends up to a height of 80 km. In this layer, once again, temperature starts decreasing with the increase in altitude and reaches up to minus 100° C at the height of 80 km.
4. Thermosphere
- Thermosphere
The thermosphere extends from 80 km above the Earth's surface. The thermosphere is the fourth layer of the Earth's atmosphere. It is found above the mesosphere. The air is really thin that high up. The temperature changes with the solar activity. If the sun is active, temperatures in the thermosphere can get up to 1,500°C or higher.
- Inosphere
The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer. Temperature here starts increasing with height.
5. Exosphere
- Exosphere
The exosphere is the uppermost layer of Earth's atmosphere. In the exosphere, an upward travelling molecule moving fast enough to attain escape velocity can escape to space with a low chance of collisions; if it is moving below escape velocity it will be prevented from escaping from the celestial body by gravity. In either case, such a molecule is unlikely to collide with another molecule due to the exosphere's low density.
Global warming is a Global phenomenon. It refers to a gradual increase in the temperature of the Earth due to trapping of green house gases. A gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels carbon dioxide, CFCs, and other pollutants. Warming of the climate system is unequivocal, and scientists are 95-100% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation. Gases such as CO2, SO2, NO2,CH4, etc. Are the green house gases. Most of these are the polluting gases that are produced by the industries. These gases trap the heat from the sunrays that are reflected from the sun.
Causes of Global Warming
It is the effect of the process of trapping of Heat due to CO2 which has been going on since times unknown. As we burn fossil fuels like coal, oil and natural gas for energy or cut down and burn forests to create pastures and plantations, carbon accumulates and overloads our atmosphere. Certain waste management and agricultural practices aggravate the problem by releasing other potent global warming gases, such as methane and nitrous oxide.
The major greenhouse gases are water vapour, which causes about 36–70% of the greenhouse effect; carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%;and ozone (O3), which causes 3-7%. Clouds also affect the radiation balance.
Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radioactive forcing from CO2, methane, troposphere ozone, CFCs and nitrous oxide.
Effects of global warming
- Sea level rise is accelerating. The planet's temperature is rising.
- Dangerous heat waves are becoming more common.The number of large wildfires is growing.
- Extreme storm events are increasing in many areas. More severe droughts are occurring in others. These are having significant and harmful effects on our health, our environment, and our communities.
Prevention Of Global Warming
The various ways to control Global Warming are:-
- Control of population. But, since it is not possible to control population, the best way to control Global warming is by planting trees - Decrease deforestation/plant forests
- Produce more fuel-efficient vehicles
- Use of ecofriendly and biodegradable products.
- Improve energy-efficiency in buildings
- Develop carbon capture and storage processes
The ozone layer in the upper atmosphere absorbs the sun’s ultraviolet radiation, preventing it from reaching the earth’s surface. This layer in the atmosphere protects life on earth from the dangerous UV radiation from the sun. The chemicals called chlorofluorocarbons or CFCs, which were used as refrigerants and aerosol spray propellants, posed a threat to the ozone layer.
The destruction of the ozone layer is seen to cause increased cases of skin cancer and cataracts. It also causes damage to certain crops and to plankton, thus affecting natures food chains and food webs. This in turn causes an increase in carbon dioxide due to the decrease in vegetation. Protecting the Ozone Layer Ban the use of CFC’s Have to replace with something Current replacements are greenhouse gases and do not eliminate ozone depletion, just slow it down.
ACID RAIN is a rain or any other form of precipitation that is usually acidic i.e. it has low pH. Acid rain is caused by emissions of Sulphur dioxide and nitrogen oxide, which react with water molecules in the atmosphere to produce acids.
Involves deposition of aqueous acids, acidic gases and acidic salts. Acid deposition has 2 parts: wet and dry - Wet deposition refers to acidic rain, fog & snow - Dry deposition refers to acidic gases and particles - Half of the acidity in the atmosphere falls back to earth through dry deposition.
Sources
Acid rain comes from chemical reactions in the atmosphere among oxygen, water and sulfur or nitrogen oxides. When sulfur dioxide dissolves in small droplets of water in clouds, it reacts with the hydrogen and oxygen of the water to form a weak solution of sulfuric acid. Similarly, nitrogen oxides form weak nitric acid in water droplets. The clouds can drift over hundreds of miles carrying their acid droplets. When conditions are right for rain, the droplets grow and fall to the ground. In many areas of the United States, such as the great plains, the acid rain falls mostly on land used for agriculture.
Causes of Acid Rain
The primary cause of acid rain is the emission of harmful gases and emissions by industrial power plants and factories, and to some extent, cars as well.
Burning of fossil fuels lead to emission of gases that give oxides of Sulphur and nitrogen.
Burning of gasoline and diesel in cars build the amount of acidified water droplets in the atmosphere.
Effects of Acid Rain
The effects of acid rain are unhealthy and harmful. Buildings, national monuments and bridges tend to deteriorate faster.
Acid rain has been found to be very hard on trees. It weakens them by washing away the protective film on leaves, and it stunts growth.
The biggest reason to find satisfactory solutions for acid rains is the damage to natural ecosystems. This rain will affect the plants, trees, rivers, lakes, soil and land wherever it may fall on.
Animals and plants that live in such areas are severely affected. Their food sources get diminished, they may develop unhealthy diseases or mutations, or they may even die in extreme cases,
EFFECT ON HUMANS
The pollutants that cause acid rain—Sulphur dioxide and nitrogen oxides damage human health. These gases interact in the atmosphere to form fine sulphate and nitrate particles that can be transported long distances by winds and inhaled deep into people's lungs. When we breathe in air pollution, these very fine particulates can easily enter our body, where they can cause breathing problems (asthma), bronchitis and over time even cause skin cancer.
Solutions for acid rain
To solve the acid rain problem, people need to understand how acid rain damages the environment. They also need to understand what changes could be made to the air pollution sources that cause the problem. Use Low Sulphur Coal The amount of Sulphur oxides emitted by a power plant can be reduced by burning coal with a very low percentage of Sulphur present.
The most important function of forests is that it produces mass amounts of oxygen as a by-product of photosynthesis. Oxygen is the main respiratory gas for all animals, it ensures our survival.
And while photosynthesis, trees also absorb carbon dioxide from the air. This is one of the main pollutants of air pollution. Hence forests also reduce air pollution.
Forests also prevent soil erosion and keep soil pollution in check. Deforestation, in fact, leads to soil erosion on a large scale since the topsoil comes loose.
Forests also play an important part in the water cycle and control moisture levels of our ecosystem.
And finally, forests are the natural home and habitat for millions of species of animals, birds, and insects.
Conserve the Forest
- Controlled Deforestation
While deforestation cannot be avoided completely, we must look to control it. Young and immature trees should not be felled as far as possible. We must look to avoid large-scale commercial deforestation as well. Adapting practices such as clear-cutting or selective cutting will be beneficial in the long run.
- Protect against Forest Fires
Forest fires are the most common and deadly cause of loss of forests. They can start due to natural causes or can be accidents caused by man or even intentional in some cases. Once a fire spreads in a forest it is very difficult to control. Precautions must be taken for such incidents. Making fire lanes, spreading chemicals to control fire, clearing out dry leaves and trees etc.
- Afforestation
This is the process by which we plant more trees in the area. We try to increase the forest cover by manual transplantation, or fresh plantation of trees. It is an attempt to balance our ecosystem to reduce the effects of deforestation and environmental pollutions of all types.
- Better Farming Practices
Slash and burn farming, overgrazing by cattle, shifting agriculture are all farming practices that are harmful to the environment and particularly to forests. We must keep all these practices under control.
Sustainable ecosystems the nation over offer a few characteristics, most outstandingly natural assorted variety. Decent variety implies an assortment of various animal categories present, yet a lot of various animal varieties present. Other vital qualities incorporate accessible real estate for meandering and extension, accessible unpolluted water source and constrained or controlled human movement.
It is a condition where population surges to a level that the earth cannot accommodate comfortably and poses a threat to the environment. 2.Unemployment: In developing countries like India with a backward economy and little scope for fruitful employment millions of people find no work to do. 3. Illiteracy Population explosion is the key reason for illiteracy in India. Because of illiteracy people are not caring the environment 4.Poor health: When there is high population growth people do not get adequate food and nutrition. Then they may suffer from poor health.
More population means more mouths to eat food which requires more agricultural production. More cultivable land has been made available by clearing forests and by reclaiming wet lands and ponds. Advanced agriculture requires utilization of more water, more fertilizers and more pesticides. And it demands more space to construct houses and availability of more consumer goods. It also requires more means of transport, more consumption of fossil fuels, and more pollution of land, air and water thus growth of population leads to pollution of land, water and air.
According to International Atomic Energy Agency (IAEA), a nuclear and radiation accidents/ hazards is an event that has led to significant consequences to people, the environment or the facility. Nuclear hazards. Risk or danger to human health or the environment exposed by the radiation emanating from the atomic nuclei is called as nuclear hazard. Nuclear hazard is an actual or potential release of radioactive material at a commercial nuclear power plant or a transportation accident.
Nuclear power plant accidents:
• The SL-1 accident(1961)
• The Three Mile Island Accident(1979)
• Chernobyl Disaster (1986)
• Fukushima Daiichi nuclear disaster(2011)
Human Health Risks
• Studies shown that the health effects due to radiation are dependent on the level of dose, kind of radiation, duration of exposure and types of cells irradiated. Radiation effects can be somatic or genetic.
• Radioactive iodine and cesium are being released into the environment from the malfunctioning nuclear reactors in Japan.
• As radioactive material decays, or breaks down, the energy released into the environment has two ways of harming a body that is exposed to it.
• It can directly kill cells, or it can cause mutations to DNA. If those mutations are not repaired, the cell may turn cancerous.
• Children are most at risk for thyroid cancer, since their thyroid glands are 10times smaller than those of adults as the radioactive iodine would be more concentrated in them. The Chernobyl accident released a plume of radioactive materials into the atmosphere in a fraction of a second. In the following years, the incidence of thyroid cancer among those exposed as children increased in Ukraine and nearby countries.
Control measures
• Laboratory generated nuclear wastes should be disposed off safely and scientifically.
• Nuclear power plants should be located in areas after careful study of the geology of the area, tectonic activity and meeting other established conditions.
• Appropriate protection against occupational exposure
• Leakage of radioactive elements from nuclear reactors, careless use of radioactive elements as fuel and careless handling of radioactive isotopes must be prevented.
• Safety measure against accidental release of radioactive elements must be ensured in nuclear plants.
• Unless absolutely necessary, one should not frequently go for diagnosis by x-rays.
• Regular monitoring of the presence of radioactive substance in high risk area should be ensured.
Noise is the unpleasant and undesirable sound which leads to discomfort to human beings. The intensity of sound is measured in decibels (dB). The faintest sound which can be heard by the Human ear is 1 Db. Due to increasing noise around the civilizations; noise pollution has become a matter of concern. Some of its major causes are vehicles, aircraft, industrial machines, loudspeakers, crackers, etc. Some other appliances also contribute to noise pollution like television, transistor, radio, etc. when used at high volume.
Types of Noise Pollution
Following are the three types of pollution:
Transport Noise
It mainly consists of traffic noise which has increased in recent years with the increase in the number of vehicles. The increase in noise pollution leads to deafening of older people, headache, hypertension, etc.
Neighbourhood Noise
The noise from gadgets, household utensils etc. Some of the main sources are musical instruments, transistors, loudspeakers etc.
Industrial Noise
It is the high-intensity sound which is caused by heavy industrial machines. According to many researches industrial noise pollution damages the hearing ability to around 20%.
Causes of Noise Pollution
Following are the causes and sources of noise pollution:
- Industrialization: Industrialization has led to an increase in noise pollution as the use of heavy machinery such as generators, mills, huge exhaust fans, etc are used resulting in the production of unwanted noise.
- Vehicles: Increased number of vehicles on the roads are the second reason for noise pollution.
- Events: Weddings, public gatherings involve loudspeakers to play music resulting in the production of unwanted noise in the neighbourhood.
- Construction sites: Mining, construction of buildings, etc add to the noise pollution.
Effects of Noise Pollution
Noise pollution can be hazardous to human health in the following ways:
- Hypertension: It is a direct result of noise pollution which is caused due to elevated blood levels for a longer duration.
- Hearing loss: Constant exposure of human ears to loud noise that are beyond the range of sound that human ears can withstand damages the eardrums resulting in loss of hearing.
- Sleeping disorders: Lack of sleep might result in fatigue and low energy level throughout day affecting everyday activities. Noise pollution hampers the sleep cycles leading to irritation and uncomfortable state of mind.
- Cardiovascular issues: Heart related problems such as blood pressure level, stress, and cardiovascular diseases might come up in a normal person and person suffering from any of these diseases might feel the sudden shoot up in the level.
Control Measures
Some noise pollution preventive measures are provided in the points below.
- Honking in public places like teaching institutes, hospital, etc. should be banned.
- In commercial, hospital, and industrial buildings adequate soundproof systems should be installed.
- Musical instruments sound should be controlled to desirable limits.
- Dense tree cover is useful in noise pollution prevention.
- Explosives should be not used in forest, mountainous, and mining areas.
The United Nations Conference on Environment and Development (UNCED), also known as the Rio de Janeiro Earth Summit , Rio Summit, Rio Conference, and Earth Summit (Portuguese: ECO92), was a major United Nations conference held in Rio de Janeiro from 3 to 14 June 1992. In 2012, the United Nations Conference on Sustainable Development was also held in Rio, and is also commonly called Rio+20 or Rio Earth Summit 2012. It was held from 13 to 22 June. Working towards international agreements which respect the interests of all and protect the integrity of the global environmental and developmental system, recognizing the integral and interdependent nature of the Earth, our home.
References:
- Textbook Of Environmental Science By Deeksha Dave And E.Sai Baba Reddy, Cengage
- Publications.
- Text Book Of Environmental Sciences And Technology By M.Anji Reddy, Bs Publication.
- Comprehensive Environmental Studies By J.P.Sharma, Laxmi Publications.
- Environmental Sciences And Engineering – J. Glynn Henry And Gary W. Heinke – Prentice Hall Of
- India Private Limited.
- A Text Book Of Environmental Studies By G.R.Chatwal, Himalaya Publishing House
