Ecosystem

Course : B.Sc. Microbiology/ Bio-Technology/ Bio-Chemistry

Sem I

Sub: Environmental Science

Unit 3.1

Environmental chemistry

• Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its source.

• It can be defined as the study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments; and the effect of human activity and biological activity on these.

• Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and soil chemistry, as well as heavily relying on analytical chemistry and being related to environmental and other areas of science.

• Environmental chemistry is the study of chemical processes occurring in the environment which are impacted by humankind's activities. These impacts may be felt on a local scale, through the presence of urban air pollutants or toxic substances arising from a chemical waste site, or on a global scale, through depletion of ozone layer or global warming.

• Environmental chemistry is a part of the environmental education.

Scopes of environmental chemistry

• At present day there are many environmental issues, which have grown day by day, threatening the survival of mankind on earth.

• The environmental chemistry is interdisciplinary in scope and integrates the fields of atmospheric chemistry, geochemistry and biogeochemistry, climate change, marine and freshwater chemistry, polar chemistry, fire chemistry, soil and sediment chemistry, and chemical aspects of ecotoxicology.

Chemical Toxicology

• Chemical Toxicology is a branch of biology, chemistry, and medicine (more specifically pharmacology) concerned with the study of the adverse effects of chemicals on living organisms.

• It also studies the harmful effects of chemical, biological and physical agents in biological systems that establishes the extent of damage in living organisms.

Hazardous Chemical

• A highly hazardous chemical is a substance classified as material that is both toxic and reactive and whose potential for human injury is high if released.

• Highly hazardous chemicals may cause cancer, birth defects, induce genetic damage, cause miscarriage, injury and death from relatively small exposures.

Highly hazardous chemicals include:

• Acetaldehyde• Ammonia• Bromine chloride• Bromine trifluoride• Cellulose nitrate• Chlorine• Diazomethane• Dibenzoyl peroxide• Ethyl nitrite • Hydrogen sulfide • Isopropylamine• Ketene• Methacrylaldehyde

and many more………..

• Nitrogen trioxide• Oleum• Propyl nitrate• Sarin• Selenium hexafluoride• Stibine• Sulfur dioxide• Sulfur pentafluoride• Sulfur tetrafluoride• Sulfur trioxide• Sulfuric anhydride• Tellurium hexafluoride• Tetrafluoroethylene• Tetramethyl lead

Carcinogen

• A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes.

• Cancer is any disease in which normal cells are damaged and do not undergo programmed cell death as fast as they divide via mitosis. Carcinogens may increase the risk of cancer by altering cellular metabolism or damaging DNA directly in cells, which interferes with biological processes, and induces the uncontrolled, malignant division, ultimately leading to the formation of tumors. Usually, severe DNA damage leads to apoptosis, but if the programmed cell death pathway is damaged, then the cell cannot prevent itself from becoming a cancer cell.

Carcinogen

• There are many natural carcinogens. Aflatoxin B1, which is produced by the fungus Aspergillusflavus growing on stored grains, nuts and peanut butter, is an example of a potent, naturally occurring microbial carcinogen. Certain viruses such as hepatitis B and human papilloma virus have been found to cause cancer in humans.

• Dioxins and dioxin-like compounds, benzene, kepone, EDB, and asbestos have all been classified as carcinogenic. As far back as the 1930s, industrial smoke and tobacco smoke were identified as sources of dozens of carcinogens

Effluent

• Effluent is an out flowing of water or gas from a natural body of water, or from a human-made structure.

• Effluent is defined as “wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters”.

• We can also define effluent as “liquid waste or sewage discharged into a river or the sea”.

• Effluent in the artificial sense is in general considered to be water pollution, such as the outflow from a sewage treatment facility or the wastewater discharge from industrial facilities.

Effluent

The natural cycles of the environment• When things happen over and over again, we call

it a cycle.• All living things depend on each other for their

needs of life.

Some Biogeochemical cycle occuring in the biosphere are:

• Carbon cycle• Nitrogen cycle• Phosphorus cycle• Oxygen cycle• Water cycle

Ozone Depletion

• Losing Earth's Protective Layer

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• The ozone layer is a belt of naturally occurring ozone gas that sits 9.3 to 18.6 miles (15 to 30 kilometers) above Earth and serves as a shield from the harmful ultraviolet B radiation emitted by the sun.

• Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly being formed and broken down in the high atmosphere

• Today, there is widespread concern that the ozone layer is deteriorating due to the release of pollution containing the chemicals chlorine and bromine. Such deterioration allows large amounts of ultraviolet B rays to reach Earth, which can cause skin cancer and cataracts in humans and harm animals as well.

Causes:

• Scientific evidence indicates that stratospheric ozone is being destroyed by a group of manufactured chemicals, containing chlorine and/or bromine. These chemicals are called "ozone-depleting substances" (ODS).

• The primary cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons).

• In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction.

• The main ODS are chlorofluorocarbons (CFCs), hydrochlorofluorcarbons (HCFCs), carbon tetrachloride and methyl chloroform.

• Halons (brominated fluorocarbons) also play a large role. Their application is quite limited: they're used in specialized fire extinguishers. But the problem with halons is they can destroy up to 10 times as much ozone as CFCs can.

Effects:• Increased UV: Ozone, while a minority constituent in

Earth's atmosphere, is responsible for most of the absorption of UVB radiation. Its depletion causes increased UV radiation.

• Biological effectsOzone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increase in skin cancer and cataract (eye damage) in human beings.

• Increased tropospheric ozone: Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. The risks are particularly high for young children, the elderly, and those with asthma or other respiratory difficulties.

• Effects on crops:• An increase of UV radiation

would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV radiation and would be affected by its increase. Thus crop growth will be affected. • NASA projections of

stratospheric ozone concentrations if chlorofluorocarbons had not been banned.

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CLIMATE CHANGE

Climate change is a significant and lasting change in the statisticaldistribution of weather patterns over periods ranging fromdecades to millions of years.

Climate change is caused by factors such as biotic processes,variations in solar radiation received by Earth, plate tectonics,and volcanic eruptions. Certain human activities have also beenidentified as significant causes of recent climate change, oftenreferred to as "global warming"

What changes climate?

• Changes in:

– Sun’s output

– Earth’s orbit

– Drifting

continents

– Volcanic

eruptions

– Greenhouse

gases

Global warming

• Global warming is the unequivocal and continuing rise in the average temperature of Earth's climate system.

• Since 1971, 90% of the warming has occurred in the oceans. Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface.

• Scientists were more than 90% certain that most ofglobal warming was being caused by increasingconcentrations of greenhouse gases produced byhuman activities.

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Greenhouse gases

• The greenhouse effect is the process bywhich absorption and emission of infrared radiation bygases in a planet's atmosphere warm its lower atmosphereand surface.

• On earth, naturally occurring amounts of greenhouse gaseshave a mean warming effect of about 33 °C

• The major greenhouse gases are water vapor, which causesabout 36–70% of the greenhouse effect; carbondioxide (CO2), which causes 9–26%;methane (CH4), whichcauses 4–9%; and ozone (O3), which causes 3–7%.

• Changes in the concentration of greenhouse gases, whichoccur both naturally and as a result of human activities, alsoinfluence Earth’s climate.

Increasing greenhouse gases

trap more heat

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• Earth’s surface absorbs heat from the sun and then re-

radiates it back into the atmosphere and to space.

• Much of this heat is absorbed by greenhouse gases,

which then send the heat back to the surface, to other

greenhouse gas molecules, or out to space. Though

only 1% of atmospheric gases are greenhouse gases,

they are extremely powerful heat trappers.

• By burning fossil fuels faster and faster, humans are

effectively piling on more blankets, heating the planet

so much and so quickly that it’s hard for Mother Nature

and human societies to adapt.

Greenhouse gases

1. Nitrous oxide

2. Methane

3. Carbon dioxide

4. Water

5. Sulfur hexafluoride

While there are many substances that act as

greenhouse gases, two of the most important

are water and carbon dioxide, or CO2.

CO2 comes from a variety of sources. For example,

plants take up carbon dioxide in the air to make wood,

stems, and leaves, and then release it back into the

air when the leaves fall or the plants die. The concern

today is that fossil fuel use is putting huge amounts of

CO2 in the atmosphere at a rate faster than the

climate system can adapt to.

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• In addition, the warming resulting from

CO2 and other greenhouse gases also

has the effect of increasing evaporation.

This adds water vapor to the

atmosphere as well.

• Water vapor is the most important gas in

the natural greenhouse effect,

contributing 60% of the effect to carbon

dioxide’s 26%. And in fact, satellites

have detected an increase in

atmospheric moisture over the oceans

at a rate of 4% per degree F of warming

(7% per degree C) since 1988. This

additional water vapor amplifies the

warming effect.

• Certainly, past temperatures past have

been lower than today, and CO2

concentrations have also varied.

• Large global swings were probably caused

by such things as changes in Earth’s orbit,

which changed the distribution of sunlight

over the planet. When this caused warming,

more CO2 and other greenhouse gases

were released, producing additional

warming.

• Earth is getting warmer by virtually every

measure we know, and the temperature

has been well above normal for more than

25 years. Although increases of 1.0-1.6°F

(0.6-0.9°C) over the last century or so may

not sound very threatening, remember

that’s a global average.

• The warming is stronger over land than

over oceans and in the higher latitudes

than in the tropics.

Sea-level rise projections

: a few inches to a few

feet

•2 ft: U.S. would lose

10,000 square miles

•3 ft: Would inundate

Miami

•Affects erosion, loss of

wetlands, freshwater

supplies

•Half of the world’s

population lives along

coasts

•Big question: Ice sheets

Why should we care?

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• Global average temperatures areexpected to increase by about 2-13°F (1-7°C) by the end of the century. That maynot sound like a lot, so what’s the bigdeal? The problem is that small changesin global average temperature can lead toreally large changes in the environment.Let’s look at some of the expectedchanges.

• There will always be natural variability, andsome places and some years will be warmeror cooler than average. In general, however,summers will get hotter, not only because ofhigher temperatures but also becausehumidities will increase. That means that heatwaves, like the one that killed 35,000 peoplein Europe in 2003, will become morecommon.

• On the plus side, winters will be warmer inmany places, reducing heating bills. And thenumber of days with frosts is likely todecrease.

Individual actions

– Tune up your furnace

Unplug appliances or

plug into a power strip and

switch it off

Use mass

transit,

bike, walk,

roller

skate

Buy water-saving appliances and

toilets; installing low-flow shower

heads.

Caulk, weatherstrip, insulate, and replace old windows

Buy products with a U.S. EPA Energy

Star label

• There are many ways society can approach

the struggle to reduce carbon emissions, but

there is no single solution. Many of the

strategies mentioned are the realm of

governments. And the ever-growing world

population means that we’ll have to work that

much harder to reduce global emissions. But

on an individual level, there are many things

you can do to make a difference.

• Air is becoming increasingly polluted –Acid Rain -- sulfur dioxide (also nitrogen

oxides) from coal burning sources + rain = ACID RAIN

Acid Rain

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Acid rain

• Acid rain is rain consisting of water droplets that are unusually acidic because of atmospheric pollution -most notably the excessive amounts of sulfur and nitrogen released by cars and industrial processes. Acid rain is also called acid deposition because this term includes other forms of acidic precipitation such as snow.

• Acidic deposition occurs in two ways: wet and dry. Wet deposition is any form of precipitation that removes acids from the atmosphere and deposits them on the Earth’s surface. Dry deposition polluting particles and gases stick to the ground via dust and smoke in the absence of precipitation.

Causes and History of Acid Rain• Acid deposition can occur via natural sources like

volcanoes but it is mainly caused by the release of sulfur dioxide and nitrogen oxide during fossil fuel combustion.

• When these gases are discharged into the atmosphere they react with the water, oxygen, and other gases already present there to form sulfuric acid, ammonium nitrate, and nitric acid. These acids then disperse over large areas because of wind patterns and fall back to the ground as acid rain or other forms of precipitation.

• The gases responsible for acid deposition are normally a byproduct of electric power generation and the burning of coal.

Effects of Acid Rain• There are several important impacts of acid deposition

on both natural and man-made environments. Aquatic settings are the most clearly impacted by acid deposition though because acidic precipitation falls directly into them. Both dry and wet deposition also runs off of forests, fields, and roads and flows into lakes, rivers, and streams.

• As this acidic liquid flows into larger bodies of water, it is diluted but over time, acids can accrue and lower the overall pH of the body. Acid deposition also causes clay soils to release aluminum and magnesium further lowering the pH in some areas. If the pH of a lake drops below 4.8, its plants and animals risk death

Effects of Acid Rain• Acid deposition can significantly impact forests. As acid rain

falls on trees, it can make them lose their leaves, damage their bark, and stunt their growth. By damaging these parts of the tree, it makes them vulnerable to disease, extreme weather, and insects. Acid falling on a forest’s soil is also harmful because it disrupts soil nutrients, kills microorganisms in the soil, and can sometimes cause a calcium deficiency.

• Finally, acid deposition also has an impact on architecture and art because of its ability to corrode certain materials. As acid lands on buildings (especially those constructed with limestone) it reacts with minerals in the stones sometimes causing it to disintegrate and wash away. Acid deposition can also corrode modern buildings, cars, railroad tracks, airplanes, steel bridges, and pipes above and below ground.

Problems from Acid Rain:

• Destruction of limestone and marble monuments due to increased chemical weathering

• Acidification of aquatic ecosystems destroying the life in them and of animals depending on them.

• Damage forests and other plants in a variety of ways

Acid – base reactions in water

• An acid–base reaction is a chemical reaction that occurs between an acid and a base.

• Acid-base reactions are ubiquitous. In aqueous solutions acids increase the hydrogen ion (H+) concentration. On the other hand bases increase the hydroxide ion (OH-) concentration. When an acid and a base react in an aqueous solution the H+ and OH- ions combine to form water. These ions thus "neutralize" one another:

• Most acids have the general formula HA, where A- is an anion and most bases have the form BOH, where B+ is an appropriate cation. Acids and bases can be grouped into two general types: strong and weak acids and bases. The difference between the two is straightforward: a strong acid in a water solution decomposes 100% into a proton (H+) and anion (A-)

• On the other hand most weak acids decompose significantly less than 100% in a water solution:

• In other words most weak acid molecules stay intact in water. Similar chemical equations hold for strong and weak bases.

•When an acid and a base are placed together, they react to neutralize the acid and base properties, producing a salt.

•The H(+) cation of the acid combines with the OH(-) anion of the base to form water. The compound formed by the cation of the base and the anion of the acid is called a salt. The combination of hydrochloric acid and sodium hydroxide produces common table salt, NaCl:

Chemistry of decaying compounds

• Decay, the breaking down, or decomposing, of dead tissue or organic matter into simpler chemical compounds. Many kinds of bacteria and such fungi as molds and yeasts bring about decay. These organisms, called saprophytes, grow and multiply on nonliving organic matter that they use as food. They release enzymes that chemically break down the organic matter into tiny nutrient particles, which they absorb. Usually, decay occurs most rapidly in warm, moist air, and away from direct sunlight. Any change in these conditions either slows down the action of saprophytes or kills them.

Stages of decomposition• Five general stages are used to describe the

process of decomposition in vertebrate animals: fresh, bloat, active and advanced decay, and dry/remains. The general stages of decomposition are coupled with two stages of chemical decomposition:

• autolysis and putrefaction.

• These two stages contribute to the chemical process of decomposition, which breaks down the main components of the body.

1. Fresh

• The fresh stage begins immediately after death when the circulatory system (heart beating/pumping blood) stops functioning. It is during this stage that the blood will settle with gravity creating a condition known as lividity. After several hours the muscles will also begin to stiffen in a process known as rigor mortis. The body temperature will also begin to acclimate to the environment. Cells will begin to break down and release enzymes during a process called autolysis which can cause blisters on the skin. The anaerobic organisms in the digestive tract will begin to multiply, producing acids and gases (the source of the bad odors). This process is often referred to as putrefaction. From the moment of death, the body begins losing heat to the surrounding environment, resulting in an overall cooling called algor mortis.

2. Bloat• The bloat stage provides the first clear visual sign that

microbial proliferation is underway. In this stage, anaerobic metabolism takes place, leading to the accumulation of gases, such as hydrogen sulfide, carbon dioxide, and methane. The gases being produced during putrefaction begin to build and will give the body a distended appearance. Gases and fluid will eventually escape through the natural orifices as the pressure builds. As the gastrointestinal bacteria multiply and can lead to conditions like marbling which is a discoloration pattern seen in the skin. The green discoloration in the abdomen areas and eventually a darkening (blackish) coloring of the skin overall as the process advances.

3. Active Decay:

• During his phase the body begins to lose much of it’s fluids and mass (tissue) through purge and insect and/or vertebrate scavenging (coyote, fox, lion, etc). During this phase you may see very large maggot masses and notice a considerable increase in foul odors.

4. Advanced Decay:• This phase is the end of the active decay process.

Temperatures can either speed up (heat) or slow down (cold) how quickly a body reaches this phase. The body has very little body mass and soil staining of the surrounding soils is still evident. This soil staining (from body fluids) may actually kill some of the surrounding vegetation temporarily. Maggots will migrate away from the body to pupate and flies will cease laying eggs.

5. Dry/Skeletal:• This phase is the last measurable stage of decomposition. The

timing of this stage varies widely by environment. If there is any skin left it will be leather-like and very tough. Mostly the body is reduced to bones and connective tissue. There is no biomass available for diverse insect colonization. Some beetles and adventitious insects may colonize a body for shelter or feeding on other insects and connective tissue. Over time the bones may “bleach” (turn white) with exposure to sunlight and eventually will begin to exhibit cracks after several years.

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Surface and Interior of Earth• Earth, the largest and densest rocky planet, was formed about

4.5 billion years ago. The Earth's interior is divided into four

layers, which is typical of rocky planets. Each layer has

different characteristics and is made of different elements and

minerals.

• There are many different types of features on Earth’s surface

due to the complexity of our planet. The surface is unique

from the other planets because it is the only one which has

liquid water in such large quantities. Water forms some

features of Earth's surface such as rivers, oceans, beaches

and lakes. Other surface features, such as

mountains, earthquakes and volcanoes, are formed when

large pieces of the Earth’s outer layer move slowly by plate

tectonics.

Layers of the earth

• CRUST -The thin, outermost layer of the earth is called the crust. It makes up only one percent of the earth's mass. This consists of the continents and ocean basins. The crust has varying thickness, ranging between 35-70 km thick in the continents and 5-10 km thick in the ocean basins. Within the crust, intricate patterns are created when rocks are redistributed and deposited in layers through the geologic processes. The crust is composed mainly of alumino-silicates. 9

• MANTLE - The mantle is a dense, hot layer of semi-solid rock approximately 2,900 km thick and is composed mainly of ferro-magnesium silicates. This is where most of the internal heat of the Earth is located. Large convective cells in the mantle circulate heat and may drive plate tectonic processes.

• CORE - Below the mantle is the core. It makes up nearly one third the mass of the earth. The Earth's core is actually made up of two distinct parts: a 2,200 km-thick liquid outer core and a 1,250 km-thick solid inner core.

• The outer core is made of iron and is very dense. As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic field.

• The inner core is made of solid iron and nickel. Many scientists believe it is kept in the solid state because of the extreme pressure from the other layers.

Formation of Rocks • The three main ways rocks are formed:• Sedimentary rocks are formed through the gradual accumulation

of sediment: for example, sand on a beach or mud on a river bed. As the sediment is buried it is compacted as more and more material is deposited on top. Eventually the sediment will become so dense that it is essentially rock. . Sandstone is a sedimentary rock formed mostly of rock particles while limestone and shale are formed mostly of organic debris. This type of rock typically is easily eroded. This process is known as lithification.

• Igneous rocks are rocks which have crystallized from a melt or magma. Most of the earth’s crust is made up primarily of cooled lava. Basically crystalline, volcanic rock can be as hard as granite or as breakable as pumice, depending on its chemical composition and how and where it cooled. Volcanic rocks that cool on or near the earth’s surface (basaltic) are much more easily eroded than those that have cooled deep within the crust (granitic).

• Metamorphic rocks: This is either igneous or sedimentary rock whose chemical structure has changed due to intense pressure, heat or chemical action. (“Meta” means change and “morph” means form.) Metamorphic rock typically is very hard and resistant to erosion. Examples are diamonds (coal –sort of), slate (shale), and marble (limestone).

• Metamorphic rocks are typically found in areas of mountain building.

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Major land forms and their transformation

• The pattern of landforms throughout the world –mountains, valleys, plains, plateaus.

• A landform is a geomorphological unit, and is largely defined by its surface form and location in the landscape. As part of the terrain a landform is an element of topography. Landform elements also include land such as hills, mountains, plateaus, canyons, valleys, seascape and oceanic waterbody interface features such as bays, peninsulas, seas and so forth, including sub aqueous terrain features such as mid-ocean ridges, volcanoes, and the great ocean basins.

Major Landforms:

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Physical characteristics• Landforms are categorized by characteristic physical

attributes such as elevation, slope, orientation, stratification, rock exposure, and soil type.

• Landforms are categorized by characteristic physical attributes such as elevation, slope, orientation, stratification, rock exposure, and soil type.

• Gross physical features or landforms include intuitive elements such as berms, mounds, hills, ridges, cliffs, valleys, rivers, peninsulas and numerous other structural and size-scaled (i.e. ponds vs. lakes, hills vs. mountains) elements including various kinds of inland and oceanic waterbodies and sub-surface features.

Landforms

Landforms are all around us.

Mountains are tall landforms that often have snow on top.

The space between two mountains is called a valley.

A plateau is like a mountain with a flat top.

Hills are like small mountains.

A river runs downhill and ends at the ocean.

Waterfalls occur when a stream or river runs over a cliff.

A canyon is formed when water runs downhill between two plateaus.

A large part of the earth is covered by oceans.

A bay is formed when water is surrounded on three sides by land.

An island is a landform that is surrounded by water.

Delta

A delta is a low, watery land formed at the mouth of a river. A delta is often (but not

always) shaped like a triangle

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Isthmus

An isthmus is a narrow strip of land connecting two larger landmasses. An isthmus has water on

two sides.

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Archipelago

An archipelago is a group or chain of islands clustered together in a sea or ocean.

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Peninsula

A peninsula is a body of land that is surrounded by water on three sides.

Strait

A strait is a narrow body of water that connects two larger bodies of

water.

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Denudation and its agents

• Denudation is the long-term sum of processes that cause the wearing away of the earth’s surface leading to a reduction in elevation and relief of landforms and landscapes.

• Endogenetic processes such as volcanoes, earthquakes, and plate tectonics uplift and expose continental crust to the exogenetic denudation processes of weathering, erosion, and mass wasting.

Denudation and its agents• Denudation processes are powered by the direct

impact of sunlight, as in insolation weathering, and indirectly in the form of thermally-driven ice, water and air gravity flows.

• Tectonic uplift elevates land surfaces into the denudational environment, thereby endowing these agents with potential energy.

• It is evident from the modern surface outcrop of rocks known to be have been emplaced below Earth’s surface, as well as from superficial rock debris and soft sediment bodies, that land surfaces are eroded and lowered over time unless disturbed by renewed uplift

Weathering

• Weathering is the breaking down of rocks, soil and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as

• water, • ice,• snow, • wind,• waves and• gravity.

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Mechanical And Chemical Weathering

• Two important classifications of weathering processes exist – physical (mechanical) and chemical weathering; each sometimes involves a biological component.

• Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice and pressure.

• The second classification, chemical weathering, involves the direct effect of atmospheric chemicals or biologically produced chemicals also known as biological weathering in the breakdown of rocks, soils and minerals

Mechanical And Chemical Weathering• While physical weathering is accentuated in very cold

or very dry environments, chemical reactions are most intense where the climate is wet and hot. However, both types of weathering occur together, and each tends to accelerate the other. For example, physical abrasion (rubbing together) decreases the size of particles and therefore increases their surface area, making them more susceptible to rapid chemical reactions. The various agents act in concert to convert primary minerals (feldspars and micas) to secondary minerals (clays and carbonates) and release plant nutrient elements in soluble forms.

Scientists are still working on thepuzzle. The IPCC’s 5th AssessmentReport is planned for 2013-2014.Climate models are being improved,more data is being collected.However, the puzzle is alreadycomplete enough to know we needto take action.

GOD BLESS MOTHER EARTH

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References

Images:

11. https://lh4.ggpht.com/cpAw8WXwrXLLKu5pVUhErB87_2TGwGgTJGBjHogEuJK91Maivg3ffAk_NjlEhgP6HKF4-pc=s132

12. http://1.bp.blogspot.com/-HkSbiBfZsjw/UmRQkebdtmI/AAAAAAAAAIQ/AumD4ALJAIw/s640/landforms.JPG

13. https://lh3.ggpht.com/URXksCVDodN07V0t1WVkOQG3n7QDXVRQDU-12KIfItCLur93beyHVulI3Ip3HGm3F-TwXA=s115

14. https://lh3.ggpht.com/zwNmfUVb7T8PVNzNLWbX2_NGCcq9cn2gnQ7ZBdZkll7jGL1C1-DfeHlkWyLdGLK-sJhXag=s103

15. https://lh4.ggpht.com/bDj5_4XzvL2RAj30TF5CYlZCTbMM-EN2FJl_mLXJjenrNL5hRvBd7uVvm3mimarirQjQJ64=s126

16. https://lh3.ggpht.com/3dLLA2gwI86P8rUxydefwXlkSA9WLUKooSsXgd64F3UH0YhTlf2V7yOtHkUChvlBFp5CQg=s75

17. https://lh4.ggpht.com/vX0vXC92uQ9paTrp46R8iLyqJeQjlokq-hmgP1zVPZrqcADjw4g-q2F2fxfnnY4E-ZM7lSE=s100

References

Books:

1. Environmental studies by R.Rajagopalan

2. Environmental Science by Richard T Wright & Bernard J Nebel

References

THANK YOU