The Hydrosphere

Over 70% of the Earth is covered by seas full of salty water. This salty water makes up about 97½% of all Earth’s water. The fresh water persons can drink is mostly ice. Only a very small amount is at hand in rivers and under the earth, for humans to drink and use. The air above the Earth stops the water from going away into outer space.
An ocean is a large area of salt water between continents. Oceans are very big and they join smaller seas together. Together, the oceans are like one “ocean”, because all the “oceans” are joined. Oceans (or marine biomes) cover 72% of our planet. The largest ocean is the Pacific Ocean. It covers 1/3 (one-third) of the Earth’s surface.
The smallest ocean is the Arctic Ocean. Different water movements separate the Southern Ocean from the Atlantic, Pacific, and Indian Oceans. The Southern ocean is also called the Antarctic Ocean because it covers the area around Antarctica. Older maps may not use the names the Arctic Ocean and the Southern Ocean.
The deepest ocean is the Pacific ocean. The deepest point is the Mariana Trench, being about 11,000 meters (36,200 feet) deep. The deep ocean is characterized by cold temperatures, high pressure, and complete darkness. Some very unusual organisms live in this part of the ocean. They do not require energy from the sun to survive because they use chemicals from deep inside the Earth.
The ocean floor, also known as sea-bed, also has mountains valleys and plains like that on land. A continental shelf is the part of the continent that is under water. The shelf was part of the land during the ice ages in the glacial periods. Beyond the continental shelf, the ocean floor goes down to much greater depths. The continental shelf is a shallow ocean. It varies in depth, up to 140 meters deep. It varies greatly in its width. At the leading edge of a moving continental plate, there will be little or no shelf. The shelf on a passive edge of a plate will be wide and shallow. The widest shelf is the Siberian shelf in the Arctic Ocean: it is 1500 km (930 miles) in width.
The shelf usually ends at a point of decreasing slope (called the shelf break). The sea floor below the break is the continental slope. The character of the shelf changes dramatically at the shelf break, where the continental slope begins. With a few exceptions, the shelf break is located at a remarkably uniform depth of roughly 140 m (460 ft); this is likely a hallmark of past ice ages when sea level was lower than it is now.
Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources. The structure of the oceans, starting with the continents, begins usually with a continental shelf, continues to the continental slope – which is a steep descent into the ocean, until reaching the abyssal plain – a topographic plain area, the beginning of the seabed, and its main area. The border between the continental slope and the abyssal plain usually has a more gradual descent and is called the continental rise, which is caused by sediment cascading down the continental slope.
The mid-ocean ridge, as its name implies, is a mountainous rise through the middle of all the oceans, between the continents. Typically a rift runs along the edge of this ridge. Along tectonic plate edges, there are typically oceanic trenches – deep valleys, created by the mantle circulation movement from the mid-ocean mountain ridge to the oceanic trench.
An ocean current is a continuous movement of ocean water from one place to another. Ocean currents are created by the wind, water temperature, salt content, and the gravity of the moon. The current’s direction and speed depend on the shoreline and the ocean floor. They can flow for thousands of miles and are found in all the major oceans of the world. Ocean currents can be found on the water surface and deeper down.
Currents on the surface often depend on the wind. They travel clockwise in the northern hemisphere. They travel counterclockwise in the southern hemisphere. They are found up to 400 meters (1,300 ft) below the surface of the ocean. Deeper currents depend on water pressure, temperature, and salt content.

Ocean currents are classified into cold currents and warm currents. Generally, currents flowing from warm tropics to poles are warm currents and currents flowing from cold tropics to tropics are cold. They also regulate the temperature of the area through which it flows and causes variation in climate.
Hydrological cycle or water cycle is the cycle that water goes through on Earth. It includes the movement of water from water bodies to the atmosphere by evaporation and return of water from the atmosphere back by condensation and precipitation.
First, water on the surface of the Earth evaporates and gets collected as water vapor in the sky. This water vapor condenses when gets cooled to makes clouds. The small droplets in clouds coalesce to form larger clouds and the water falls from the sky as rain, snow, sleet, or hail which is called precipitation. This water sinks into the surface and also collects into lakes, oceans, or aquifers. It evaporates again and continues the cycle.

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Economic Planning in India

Our leaders were very much clear that there is a need for planned growth of the economy to overcome the underdeveloped status of newly independent India. Many of our leaders were inspired by the soviet model of development and decided to go for a similar planned development strategy. The planning commission was established under the chairmanship of Prime Minister and was designated with the job of creating five-year plans for developing India.

Five-year plans are documents describing the growth targets, estimates if resources, priorities and strategies etc.

The second five-year plan designed by P C Mahalanobis was instrumental in pursuing the unbalanced growth strategy by focussing on basic goods and capital goods industries so that the forward linkages will propel the higher levels of production. This strategy was followed till the 1980s. But failure in creating forward linkages and high level of imbalance forced us to change the focus from basic goods to consumer goods.

Planning in India includes Indicative planning and Imperative planning. Indicative planning is when the direction of policy is given by the plan document and stakeholders are motivated to follow the suit. There may be some incentives for following the plan direction. But it is not mandatory for stakeholders. But in the case of imperative planning, the plan is binding on all stakeholders. India has a mixture of both plans because some of the provisions are mandatory and non-confirmation can be penalised.

Indian planning is unique in the sense that it includes Economic Planning and Social Planning. It talks about economic goals as well as social goals.

First Five Year Plan:
The first plan had a huge emphasis on agriculture. The economy was stagnant at the time of independence and there was an acute shortage of food grains.Industries in India was not developed enough and primarily consisted of cottage industries.Our exports were limited to primary products. We targeted a growth rate of 2.1% and achieved 3.6% in the first five-year plan designed by K. N Raj.

Second Five Year Plan:
Second Plan was designed to ensure rapid industrialisation. We could improve the share of industries in GDP from 3% to 18%. We also attained a growth rate of 4.2% against the target of 4.5%. The food shortage was still an issue and we had to manage with imports from the US.

Third Five Year Plan:
The objective of the third five-year plan was a Self-reliant and Self-sustained economy. We wanted to increase the production to a level where we can overcome the need to import things and this was called ‘Import Substitution’. We started Public Sector Units (PSU) to ensure production levels.
An economy can be self-sustained only when there is a huge growth rate. Issues in minor sectors should not affect the overall growth and development, and high growth rate will cushion the impact of minor issues. Though we wanted to attain self-sufficiency in Technology, Consumer Goods and Capital Goods, we were far away from actual self-reliance due to the shattered state of the economy at independence. Industries were set up in many sectors, only after Independence.
We had an ambitious target of 5.6% growth rate in this plan and we could achieve only 2.7% and the plan was officially declared as a failed plan.

Reasons for the failure of this plan includes the Leadership crisis after the demise of Nehru, Wars with China and Pakistan and Failure of monsoons.

Annual Plans/Rolling Plans:
Between 1966 and 1969 we had three annual plans and achievements of this period was green revolution.

Fourth Five Year Plan:
Self-reliance was the objective of the fourth five-year plan with emphasis on growth and stability. Our targets were at the level of the third plan itself we could achieve only 3.3% growth. Inflation was highest with problems of shortage of money with the government. 1971 war and oil crisis of 1972-73 due to Suez Canal Issue also affected this plan. However, this plan was not officially declared as a failure.

This plan was marked by aggressive policies of Indira Gandhi, like Nationalisation of Banks, the passage of Monopolistic and Restrictive Trade Practices Act to control industries and Foreign Exchange Regulation Act to control foreign exchange.

Fifth Five Year Plan:
Though the theme was Poverty Eradication, there were no schemes for the same in first three years as the plan design was more due to political need from agitations in the country by Jayaprakash Narayan. It went through the National Emergency and ultimately resulted in first non-Congress government.

Annual Plans:
Between 1979 and 80 we again had annual plans due to political instability.

Sixth Five Year Plan:
This plan was designed by Planning Commission itself and had an emphasis on Structural Change of the Economy. We wanted to induce faster development in the secondary and tertiary sector.We introduced Industrial Policy of 1980 to enable faster Industrial Development. Huge profits incurred by PSUs and the need for resources to run Employment generation and Poverty eradication schemes left government at a handicap to invest more and the only remaining choice was to allow the private sector to play a significant role. Hence we started liberalisation of licensing and perspective planning with long term goals.

Seventh Five Year Plan:
This plan was also designed by Planning Commission and talks about modernisation. This plan is almost similar to the previous one and had its emphasis on liberalisation. The plan wanted to promote investment in technology to modernise existing plans as well as to expand the economy to promote modern sectors like food processing and electronics.

The political instability resulting from the internal politics and Bofors Scam lead to economic crisis during this period and we faced the biggest crisis during this period. Credit rating agencies reported that India may default and USSR was not in a position to help due to their internal problems. Hence, we were forced to go for non-concessional assistance(high-interest short-term loans) and was forced to pledge gold to Banks ofJapan England and Switzerland.

Annual Plans:
1991 and 1992 we had annual plans with congress governments with a thin majority. We got a conditional loan from IMF and we announced ‘ The New Industrial Policy-1991.

Eighth Five Year Plan:
The plan, developed by John W Miller focussed on Human Resource Development and reforms were directed towards Liberalisation, Privatisation and Globalisation. In spite of many changes in government, the plan was not postponed.

Ninth Five Year Plan:
Ninth Plan aimed at equitable distribution and growth with equality and we could achieve a growth rate of 5.4%. There was a sudden decline in growth rate due to South East Asian Crisis, Sanctions after the nuclear test, Kargil War and the terror attack in the US.

Tenth Five Year Plan:
This plan was affected by the global slowdown in 2003-04. 2004 showed a sudden boom and African Countries were growing at 6%.

Eleventh Five Year Plan:
The objective was Inclusive development.

Twelfth Five Year Plan
Faster, More inclusive and Sustainable Growth

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Sectors of the Economy & The Need for Unbalanced Growth Strategy

The economy is primarily a system of production of goods and services. This production is classified into three different sectors for a clear understanding of the structure of the economy and for effective design and implementation of development strategies.

The first sector is called Primary Sector and it is related to extraction of raw materials. Natural resources are transformed into primary products in this sector, which are further used by other sectors. This sector includes Agriculture, Fishing, Forestry, Mining and Quarrying.

The second sector is called Secondary Sector and is mainly concerned with manufacturing. This sector uses the products of primary sector(raw materials) and adds value to it by modifying it and transforms them into goods.

‘Tertiary Sector’ is the third one which is related to the provision of services to customers and businesses. Hence, it is also called service sector.

As per the ‘Three sector hypothesis’ in economic theory, the main focus in an economy shifts from Primary sector, through the secondary sector and finally to Tertiary sector. Development is identified as the structural change in the economy from primary to later ones. It is supposed to lead to increased quality of life, reduction of poverty and unemployment, improvement of education, etc.

Though there is a gradual change in the structure of the economy during development, all the sectors also grow in quantity. In an underdeveloped economy primary sector will be responsible for most of the production, say 80% for an example. While development is happening the share shrinks to maybe 60% of GDP. But during the same period, the size of the economy will also increase from 10 crore rupees to 15 crore rupees. So, what was 80% translates to 8 crores in the initial times while 60% of 15 crores becomes 9 crores. You can see that there is a growth in the size of all sectors in spite of the change in structure and reduced share of some sectors.

In India, we classify industries into, four different types. Capital Goods Industry, Basic Goods Industry, Intermediate Goods Industry and Consumer Goods Industry. Capital Goods Industry includes the industries that manufacture plants and machines used to produce other goods. Basic Goods industries are those core industries which may not be directly contributing much value to the economy, but are unavoidable for the growth of the economy. This includes Petroleum, Coal, Gas, Cement, Fertilizer etc. Sometimes a product from one industry may be a raw material for another industry. Such Industries which produce goods which connect two sectors are called Intermediate Goods Industry. For example, steel can be an intermediary good which is used to make heavy machinery in a capital goods industry or in making a household instrument in consumer goods industry. Consumer Goods Industry includes all the goods which are used by general public in common.

Consumer goods are again divided into durable goods and non-durable goods. Non-Durable goods are those perishable goods which we consume immediately after purchasing. It includes all the consumables which we use up in short time period like Food Items, Toiletries etc. Durable goods are those goods which can be used repeatedly for a longer period of time. The Electronic instruments, utensils etc are classified as durables. They are also called white goods as they were initially made up of steel or aluminium which is white in colour. For statistical purposes, the difference between these two types of goods is taken as a minimum shelf life of 3 years.

The debate among policy makers who try to induce development was that whether the development should be balanced or unbalanced. In a balanced growth strategy, the government gives equal importance to all sectors of the economy and tries to develop them equally. But in the case of an unbalanced growth strategy, the government focuses only one of the sectors and wait for others to develop on its own.

Those who support unbalanced strategy argues that the sectors in the economy are interlinked and expansion in one sector will force the growth in other sectors. For example, if government actively develops sugar industry, the demand for sugar cane will go up. The demand causes the increase in price and attracts more farmers to grow sugar cane. This is how due to the backwards linkage of sugar industry sugarcane agriculture develops. similarly, if there is surplus sugar and price of sugar come down the industries like sweets manufacturing, using sugar as a raw material will increase their production. Seeing their success more such industries will come up. Due to the forward linkage, more sectors develop. If the backwards and forward linkages of an industry are not capable of pulling up the related industries, the growth will not be sustainable and will be of short duration only.

Economic constraints of the economy also is a reason for unbalanced growth strategy. As the government doesn’t have enough money to invest in all sectors, it carefully chooses and invests in those sectors which have more linkages and can make whole of the economy move.

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Social Development and Alternatives to GDP

We saw in the previous article, how the growth can be quantified. Now let us see how the development can be measured, or quality of growth can be measured. The quality of development is measured using social indicators of development which gives the level of improvement of the social situation of the people.

The first attempt to measure social development came from Morris in 1970s. He developed an index called, Physical Quality of Life Index(PQLI). It included, a) Life Expectancy, b) Infant Mortality Rate and c) Literacy Rate.

Life expectancy at birth is expected life-span of an individual calculated based on national statistics. Infant Mortality Rate(IMR) is the rate of death of infants(less than 1-year old) in 1000 live births. Literacy rate indicates the percentage of adults who are literate.

Major development in the measurement of social development was the publication of Human Development Report by UNDP in 1990, which had Human Development Index which combines both the concepts of Social Development and Economic Development. It encompassed, a) Life Expectancy, b)Level of Education and c) Percapita Income. The level of Education is a combination of ‘Mean years of schooling’ and ‘Expected years of schooling’. Earlier they used Literacy rate and enrolment ratio. But enrolment ratio failed to give a real picture due to high drop out rates.

Per Capita Income is calculated by dividing National Income by population. It is an indicator of the average wealth of the citizens of the country.

Other important measurements are HPI, GPI, GNH, Green GDP, etc.

Human Poverty Index (HPI) focusses on the level of poverty in a country. It was developed by UN and it indicates the standard of living in a country. It includes lifespan, functional literacy, long-term unemployment, relative poverty, etc.

Genuine Progress Indicator (GPI) is a measure of sustainability and inclusiveness in growth pattern. It is claimed to be distinguishing the growth from uneconomic growth where inequalities increase rapidly with economic development. It attempts to see whether the increase in production of goods and services actually impacted in improvising the well being of the people.

Coined by Jigme Singye Wangchuk, Former King of Bhutan, Gross National Happiness or Gross Domestic Happiness is an indicator which includes spiritual element to development. It includes a) Promotion of equitable and sustainable socio-economic development, b) Preservation and promotion of cultural values, c) conservation of natural environment, and d) establishment of good governance. It changes the focus of development from economy to spiritual and physical development in harmony.

Green GDP is primarily a sustainability based concept which focuses on environmental consequences of development. Cost of ecological degradation is deducted from GDP to attain this value.

The concepts of social development includes Health, Education, Availability of Drinking Water, Sanitation etc. The government of India actively intervenes to improve social devbelopment by various health and education sector schemes like, National Health Mission, Janani Suraksha Yojana, Sarva Siksha Abhiyan, Swach Bharath Abhiyan etc.

Development is a result of careful planning and implementation of those plans to ensure a positive change in health education etc. Implementation of plans to cause development needs financial inputs which are derived from economic growth. So Growth is inevitable for development. But Growth can happen without development, if the governemnt ignores the social aspect and concentrates only on economic growth.

Thus we see that growth is a necessary precondition to development. There are two factors which influences growth and development. They are capital formation in the economy and increase in productivity of unit capital in the economy.

For production to increase, there should be an increase in number of production units and increased amount of work in the existing production unit. This is done by capital formation. People save a percentage of what they earn, by keeping it in various bank accounts. Banks use this money for lending to the industries. This loans serves as the capital investment for industries to increase the production capacity or to add new production units, and in the end increases the growth. This percentage of GDP getting invested as capital is called rate of capital formation and is important factor of growth.

The other factor of production is productivity of capital. If 1 crore rupees is invested in a textile mill and it produces 1.2 crore worth textiles per year, the productivity of capital is 120 percent. This is also measured as capital output ratio(COR).

COR = Total Invested Capital/ Monetary Value of Output Produced

In the first case COR will be 1/1.2 ie, 0.833. You can see that COR decreases with increase in productivity of capital.

Now we have to see, what will be the contribution of addition of more capital into the factory. Suppose, we increase the capital to 1.1 crore and the production increases to 1.25 crore. The production has increased but the productivity of capital decreased and COR is approximately 0.88. We can see that addition of 0.1 crore rupees to capital increased the production by 0.05 crore and if we take the ratio between increased capital and increased production it is equal to 2. This ratio between increased capital and increased production is called Incremental Capital Output Ratio(ICOR).

ICOR = Increment in Capital/Increment in production.

The growth in an economy depends on rate of capital formation and productivity of additional investments. Productivity of investment is inversely related to ICOR. Hence we can deduce that, the growth rate of an economy is the divident of capital formation by ICOR.

Growth rate = Rate of Capital Formation/ICOR

So, to increase growth rate of economy we can either increase the capital formation or decrease ICOR. Rate of capital formation cannot be unlimited as we know that the saving is only the surplus earning of the people after consumption for their day to day needs. But we can decrease ICOR by improving the efficiency of production.

For example, If the additional 0.1 crore invested in the textile mill was to buy a new machinery, capable of doing more weaving at lower energy requirement and labour, the production would have increased to 1.3 crore. In this case COR would have been approximately 0.79 and ICOR would have been 1. The growth would have been better. The examples clearly shows that the growth can be brought about by improvement in technology of production or technology upgradation.

Comparing all these we can summarise that development includes social and societal improvemnt along with economic growth and we can enable growth by improving technology. Now we will move on to different sectors in a national economy in the next article.

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The Concept of GDP and Factors of Growth & Development

We already learned that Economics is a science related to production, distribution, trade and consumption of goods and services. Hence it studies about available resources and their utilisation to satisfy needs and wants of people. We will be talking a lot about ‘Economy’ while we discuss economics like ‘Indian Economy’, Economy of a country, Global Economy etc. In such references, the term ‘Economy’ means an ‘Economic System’ or a group of economic institutions and individuals operating under same regulations. Continue reading “The Concept of GDP and Factors of Growth & Development”

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Introduction to Economics

At the beginning of humanity, the man was a hunter and gatherer and nature provided food in surplus for entire humanity. But there were seasons of distress when rain was insufficient or trees didn’t bear fruits. Man learned that there are some fruits which can be kept in a cave or a hole in the tree while he gets it in surplus, and use it during the distress season. He understood that if one person has mangoes in surplus and other has grapes in surplus, both of them can exchange the surplus to have some amount of both. This household transactions and habits was beginning of the discipline called Economics. Unsurprisingly, the word Economics comes from greek words meaning ‘household management'(‘Oikos’= Family, Household, Estate; ‘Nomos’= Custom, law) and essentially means management of resources which are scarce. Economics is a logical application of intelligence to human choices about utilisation of resources and it encompasses activities of production, distribution, trade and consumption of goods and services. Continue reading “Introduction to Economics”

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Erosion & Deposition

As you know, the river is a body of flowing water. It flows down the slope under the effect of gravity, in a valley. The origin of the river is called source and the place where it ends, merging with a large water body is called the mouth.
Force of flowing water causes a dragging effect on river bed causing erosion and deepening of the valleys. Rivers also erodes the banks and widens the valleys. Sometimes soluble components are dissolved in water causing further erosion.
In the upper part of the river, as they are flowing from a great height, the velocity of flow will be higher and there will be a faster erosion of river bed. As a result, there will be the formation of deep and narrow ‘I’ shaped valleys called Gorges. Waterfalls or rapids are formed when a softer rock which is easily eroded comes after a layer of the hard rock layer.
When rivers erode the branches and widen the valleys the bank will be gently sloping leading to ‘v’ shaped valleys.
The river transports the eroded materials along with their flow and the number of materials carried depends on the speed of flow. Some materials are carried by the river in dissolved form while some are carried as suspended particles(suspended load). Coarse and heavy materials are dragged along the river bed as bed load.
In the later course of a river, it slows down and the carrying capacity also comes down. Excess load gets deposited on the riverbed and along the banks. Mainly it raises the river bed and the river becomes shallow and wide. When the deposits reach the level of flow of water the river gets bifurcated into multiple channels and riverine islands may be formed when some of these channels rejoin. Such a channel is called a braided channel.
Rivers deposits heavier particles at an earlier point and lighter particles further downstream. When river bed raises due to deposition of sediments, the river will show a tendency to overflow their banks. Such areas where rivers overflow, depositing rich and fertile soil is called flood plains. As the flow reduces, the amount of deposition also reduces away from the channel leading to accumulation of deposition along the banks. They are called natural levee.
In the flood plains, there can be the formation of broad curves due to flooding and changing course of rivers. This tendency is called meandering tendency. Such a meander loop can become cut off from the river stream by further deposition leading to the formation of an Oxbow Lake.

When the river reaches the mouth, if it is sufficiently loaded with sediments, can deposit them at the mouth causing the formation of triangular land forms, They are called deltas. As the delta gets enlarged the mouth of river shifts further and some area which was earlier under the oceans or seas are reclaimed as land. Because of depositional activity, the river stream may split into multiple channels and they are called distributaries.
The water seeping underground becomes ground water and it also causes some erosion and formation of landforms. This is more clearly seen in limestone region and is called Karst topography.
Water seeping underground fills the gaps and spaces in rock strata and flows down till it reaches a zone of saturation where all the spaces are filled with water. This area is called water table. The depth of water table differs from area to area.
While water seeps underground through the fractures in limestone, it dissolves the stone in due course of time due to carbonisation. This results in large underground caves and passages. Some of them may carry underground streams and some of these streams may reappear on the surface as springs.
As groundwater containing dissolved lime or calcite drips from the roof of the caves, the water evaporates leaving calcite behind. These deposits hanging from the cave ceilings are stalactites. When similar deposition happens upwards from the floor of the cave, they are called stalagmites. Some of them may join together to form pillars inside the caves.
Wind action of gradation is mostly limited to dry arid areas especially deserts. Erosion happens when loosely bounded particles are carried away by the wind causing wind eroded basins. These particles are deposited over other areas when there is an obstacle lying in its path creating sand dunes of varying sizes and shapes. Sand dunes usually have a gentler slope towards the windward side and are convex from that side.
Glaciers are formed on top of high mountains and in subarctic zones. When the glacier is huge, the lowest layers will be slightly plastic and they slowly flow in the direction of the slope. A glacier behaves like a slow moving river of ice.
Glaciers are categorised by their morphology, thermal characteristics, and behaviour. Alpine glaciers, also known as mountain glaciers or cirque glaciers, form on the crests and slopes of mountains. An alpine glacier that fills a valley of a former stream is sometimes called a valley glacier. A large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have an area less than 50,000 km2 (19,000 sq mi) by definition.
Glacial bodies larger than 50,000 km2 (19,000 sq mi) are called ice sheets or continental glaciers. Several kilometres deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland.
As the glaciers expanded, due to their accumulating weight of snow and ice, they crush and abrade scoured surface rocks and bedrock. The resulting erosional landforms include cirques, glacial horns, arêtes, U-shaped valleys, over deepenings and hanging valleys. Cirque is the starting location for mountain glaciers.U-shaped valleys are created by mountain glaciers. When filled with ocean water so as to create an inlet, these valleys are called fjords. Arête is a spiky high land between two glaciers, if the glacial action erodes through, a spillway forms.

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Rock Cycle & Weathering

All places on Earth are made of or are on top of rocks. A rock is a naturally occurring solid made up of a mixture of one or several minerals, in varying proportions. The minerals in the rocks vary, making different kinds of rock. The Earth’s crust is made of rock. Rock is often covered by soil or water. Rock is beneath the oceans, lakes, and rivers of the earth, and under the polar icecaps.

Minerals are usually solid, inorganic, crystalline substances formed naturally by geological processes. A mineral is a homogeneous naturally occurring substance with a definite but not necessarily fixed chemical composition. Most minerals are solids with an ordered atomic arrangement made of a single chemical element or more usually a compound. There are over 4,000 types of known minerals.
Rocks are classified by their minerals and chemical make-up.Rocks are aggregates of minerals. Geologists divide rocks into three groups: igneous, metamorphic, and sedimentary. Igneous rocks crystallise from magma. Metamorphic rocks form by the deformation and/or recrystallization of pre-existing rock by changes in temperature, pressure, and/or chemistry. Sedimentary rocks form by weathering and erosion of pre-existing rock to make sediment, which is lithified into rock.

Igneous rocks are formed when molten magma cools, either above or below the surface. They are divided into two main categories: plutonic rock and volcanic rock. Plutonic or intrusive rocks are made when magma cools and crystallises slowly within the Earth’s crust (example granite). Volcanic or extrusive rocks result from magma reaching the surface either as lava or ejecta (examples pumice and basalt).
Sedimentary rocks are the most common rocks on Earth. They form at or near the Earth’s surface. Sedimentary rock is formed in layers which were laid down one by one on top of another. Some of the layers are thin, some are thick. Layers are made by deposition of sediment, organic matter, and chemical precipitates. Deposition is followed by squeezing of sediment under its own weight, and cementation. This process is called ‘consolidation’: it turns the sediment into a more or less hard substance.
Metamorphic rocks are secondary rocks formed by rocks transformed under great pressure and high temperatures under earth’s crust. These conditions change the make-up of the original minerals.
The rock cycle is the process by which rocks of one kind changing into rocks of another kind. Three types of rocks can change into the other kinds by physical processes: cooling, melting, heat, weathering/erosion, compacting (squeezing tightly together), cementing, and pressure. Other substances also can become rocks and enter the rock cycle. When heated deep underground, rocks become magma (liquid rock). Above ground, it is called lava. Sediment, the particles from rock erosion and weathering, is the basis for a sedimentary rock of the future and soil may be reconverted to rock by this process.
These processes can occur in different orders, and the cycle goes on forever. Wind and water can create sediment from rocks, and movement of one tectonic plate against another creates enormous heat and pressure which affects rocks greatly. Subduction converts all kinds into magma, which eventually rejoins the cycle as igneous rock.
Weathering is the breaking down of rocks, soil and their minerals through direct contact with the Earth’s atmosphere, waters, or living things. Weathering occurs in situ (in place, with no movement). It leads to erosion. Erosion is where rocks and minerals are moved downhill (usually towards the sea) by water, ice and the wind.
The two main types of weathering are physical and chemical. Sometimes there are also aspects of biology. Physical weathering is important 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. The materials left after the rock breaks down combined with organic material creates soil.
Mechanical or physical weathering means the breakdown of rocks and soils through direct contact with atmospheric conditions such as heat, water, ice and pressure. It is the mechanical disintegration of rocks without a change in chemical components.
Wind processes are called ‘aeolian’. The Wind erodes the Earth’s surface by removing loose, fine-grained particles, called ‘deflation’. Sand carried by the wind wears down surfaces. Regions which have intense and sustained erosion are called deflation zones. Most aeolian deflation zones are composed of desert pavement, a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles. Almost half of Earth’s desert surfaces are stone deflation zones. The rock mantle in desert pavements protects the underlying material from deflation.
Rain is another force that works slowly. The force of raindrops on some rocks makes them wear down. Rain also can make a chemical change in some rocks, because it is usually slightly acidic. The water mixes with the minerals in the rock to break it down.
Changing temperature can make a rock crack. Every day when the sun shines on the rock, its surface is heated. Heat causes the surface to expand (get bigger) a little. The inside of the rock, though, does not heat up as fast as the outside of the rock. The inside of the rock stays cooler. At night, the surface cools down and contracts. The expanding and contracting makes some places on the surface weak, and a crack is made. Also, if water gets into a crack in a rock and the temperature goes below the freezing point, the water will freeze and expand. After some time, the rock may be weak enough to break into pieces.
Ice, which can be miles thick, grinds the surface of the rock below it. The particles are carried with the ice, and if a glacier ends up in the sea, so does all the material carried with it.
Lava or magma can cause weathering as when the molten rock touches rock (either intrusive rock extrusive) it causes the rock to change form to add to the quantity of molten rock causing the rock to have changed form. So the rocks have formed a different crystal structure to before it came in direct contact with the lava or magma.
Chemical weathering is the direct effect of atmospheric or biological chemicals in the breakdown of rocks, soils and minerals. The mineral composition of rock changes due to chemical reaction with water or air. The carbon dioxide cycle is the most important for weathering. CO2 is put into the atmosphere mostly by volcanoes, and it is taken out of the atmosphere by photosynthesis, and by one other process. While it is in the air, CO2 can dissolve in water droplets to form dilute carbonic acid.
When rain hits a rock it does so with mechanical energy and dilute acid. The acid dissolves many types of minerals and rocks though, of course, very slowly. When a mineral like feldspar is dissolved, it lets sodium ions into the sea; chlorine ions come from other minerals. The sea tastes salty because of the elements which have been dissolved out of rocks.
Biological weathering happens when animals mechanically burrow or when plants and trees extend their roots into rock strata breaking it up.
Due to weathering, the particles are loosened up and under the effect of gravity, they are pulled downward. This movement under the influence of gravity is called mass wasting or mass movement.
The mass movement of soil and rock materials gets saturated with water and flows downward with water across a gentle slope, it is called earth flow. Similar flow occurring downwards a steep slope is called mud-flow. Dry soil and rock pieces suddenly flowing downhill across a steep slope is called a landslide.
Weathering is important for soil formation. The soil is a combination of fine rock particles and organic materials called humus. Humus is derived from remains of plants and animals. Soil formation is a slow process taking hundreds of years. Soil formation happens in layers and these layers can be seen distinctly if we dig a pit. The arrangement of horizontal layers of soil is called soil profile.
The topmost layer of soil is called topsoil and contains clay, silt, sand and humus. Most of the plants extend their roots in this layer. The layer below it is called subsoil. It contains coarse clay, sand and minerals. Partially weathered rocks and bedrock are seen below it.
As a consequence of weathering, the rock strata gets disintegrated and transported downwards to get deposited at lower places. Running water, glaciers, winds and sea waves causes this movement and are called agents of gradation. They erode, transport and deposit the earth material along their course of movement. In this process, they continuously change the landscapes and creates new land forms.
Running water in the form of rivulets, streams and rivers is the most important agent of gradation. While waterfalls on the earth’s surface some of them will get soaked into the earth and the remaining flows on the surface of the earth as run-off. Run-off depends on the slope of the land, amount of rainfall and extent of vegetation in the area. The water washes away the topsoil and reduces the fertility. This is called as soil erosion.
During heavy rainfall entire layer of soil is washed off from a large area without plant cover. Such erosion is called sheet erosion. Gully erosion is when rainwater scoops out the soil creating narrow deep channels called gullies while moving down the slope in uneven terrain.

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Landforms & Plate Tectonics

The surface of the Earth is not even. There are high places called mountains, and high flat places called plateaus. There are low places called valleys and canyons and relatively flat areas called plains. For the most part, moving air and water from the sky and seas damages rocks in high places and breaks them into small pieces. The air and water then move these pieces to lower places.
We have already seen that the solid thin lithosphere rests on plastic asthenosphere. The lithosphere is of two types, Oceanic and Continental. Oceanic lithosphere is associated with oceanic crust and exists in the ocean basins. Oceanic lithosphere is typically about 50–100 km thick. Continental lithosphere is associated with continental crust. Continental lithosphere has a range in thickness from about 40 km to perhaps 200 km, of which about 40 km is the crust.
The lithosphere is divided into tectonic plates, which move gradually relative to one another. Plate tectonics is the theory developed to explain large scale motions of the Earth’s lithosphere. This theory builds on older ideas of continental drift and seafloor spreading. Exactly how this happens is still not understood and the driving forces moving the plates continue to be active subjects of research.
Although solid, the asthenosphere can flow like a liquid on long time scales. Large convection currents in the asthenosphere transfer heat to the surface, where plumes of less dense magma break apart the plates at the spreading centres and cause the movement of plates. The deeper mantle below the asthenosphere is more rigid again due to extremely high pressure.
The lithosphere is divided into eight major and many minor plates. These lithospheric plates ride on the asthenosphere at one of three types of plate boundaries convergent boundaries, divergent boundaries or transform fault boundaries. Tectonic plates can create mountains, earthquakes, volcanoes, mid-oceanic ridges and oceanic trenches, depending on which way the plates are moving.
A convergent boundary is where two or more tectonic plates collide with each other causing massive earth movements. The Himalayas were formed by such a collision. Earthquakes and volcanoes are common near convergent boundaries. This is because of pressure, friction, and plate material melting in the mantle.

There can be two types of subduction in a convergent plate boundary. When Oceanic crust moves under, a deep ocean trench forms at the coast and an arc of mountainous volcanoes form inland as seen along the western edge of the Americas. But, when continental crust moves under, the edge of the continental plate folds into a huge mountain range. Behind it is a high plateau. The Himalayas and the Tibetan plateau are a perfect example of this. Folds can be upfolds(anticlines) or downfolds(synclines).

A divergent boundary, also known as a constructive boundary, is two or more plates that move apart from each other because of plate tectonics. When they move apart either water or magma fills the space. If it is magma, when it has cooled it then creates a new plate which then creates new land.
A fault is a fracture, or break, in the Earth’s crust (lithosphere). Some faults are active. Here, sections of rock move past each other. This sometimes makes earthquakes. Faulting occurs when shear stress on a rock overcomes the forces which hold it together. The fracture itself is called a fault plane.
An earthquake (or quakes, tremors) is shaking caused by sudden movements of rocks in the Earth’s crust. They can be extremely violent. Earthquakes are usually quite brief but may repeat. They are the result of a sudden release of energy in the Earth’s crust. This creates seismic waves, which are waves of energy that travel through the Earth. The study of earthquakes is called seismology. Seismology studies the frequency, type and size of earthquakes over a period of time. The magnitude of an earthquake and the intensity of shaking is usually reported on the Richter scale. On the scale, 3 or less is scarcely noticeable, and magnitude 7 (or more) causes damage over a wide area. Earthquakes are caused by tectonic movements in the Earth’s crust. The main cause is that when tectonic plates collide, one rides over the other, causing orogeny (mountain building), earthquakes and volcanoes.
An earthquake under the ocean can cause a tsunami. This can cause just as much death and destruction as the earthquake itself. Landslides can happen, too. Earthquakes are part of the Earth’s rock cycle. Tsunami or a chain of fast moving waves in the ocean caused by powerful earthquakes is a very serious challenge for people’s safety and for earthquake engineering. Those waves can inundate coastal areas, destroy houses and even swept away whole towns.
A volcano is a mountain where lava (hot, liquid rock) comes from a magma chamber under the ground. Most volcanoes have a volcanic crater at the top. The magma which reaches the earth’s surface is called lava and the path through which it comes out is called a vent. When a volcano is active, materials including lava, steam, gaseous sulphur compounds, ash and broken rock pieces come out of it. When there is enough pressure, the volcano erupts. Some volcanic eruptions blow off the top of the volcano. The magma comes out, sometimes quickly and sometimes slowly. Some eruptions come out at a side instead of the top.
The lava and pyroclastic material (clouds of ash, lava fragments and vapour) that comes out from volcanoes can make many different kinds of land shapes. There are different types of volcanoes based on the type of lava and manner in which it flows.OR Volcanoes are classified on the basis of nature of eruption and the form developed at the surface.
Shield volcanoes are the largest of all the volcanoes on the earth. They built out of layers of lava from continual eruptions (without explosions). These volcanoes are formed by fluid low-silica mafic lava. Because the lava is so fluid, it spreads out, often over a wide area. Shield volcanoes do not grow to a great height, and the layers of lava spread out to give the volcano gently sloping sides. Shield volcanoes can produce huge areas of basalt, which is usually what lava is when cooled. The base of the volcano increases in size over successive eruptions, where solidified lava spreads out and accumulates. Some of the world’s largest volcanoes are shield volcanoes.

A cinder cone volcano is a tall, conical volcano. Unlike shield volcanoes, cinder-cone volcanoes have a steep profile. The lava that flows from stratovolcanoes cools and hardens before spreading far as it has high viscosity. The magma forming this lava is often felsic, with high-to-intermediate levels of silica, and less mafic magma. Big felsic lava flows are uncommon but have travelled as far as 15 km.
A series of successive eruptions of different types of lava gives rise to composite volcanoes. These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt. There will be alternate layers of lava, cinder and ash.
Volcanoes are commonly seen at convergent plate boundaries. When two plates meet, one of them (usually the oceanic plate) goes under the continental plate by the process of subduction. Afterwards, it melts and makes magma (inside the magma chamber), and the pressure builds up until the magma bursts through the Earth’s crust.
The second way is when a tectonic plate moves over a hotspot in the Earth’s crust. The hot spot works its way through the crust until it breaks through.
As volcanoes and earthquakes are results of tectonic movements, they are seen concentrated around plates and there are areas where they are very common like ‘Pacific ring of fire’ around the Pacific Ocean.
Orogeny is the process of mountain-building. It takes place when two tectonic plates come together. Mountains develop while a continental plate is crumpled and thickened and involve a great range of geological processes. This is called folding. Mountains can also be formed when faults occur. A fractured area of crust may dip down leading to the elevated area forming the mountain. Volcanism can also lead to mountain formation by deposition of magma.

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The Structure of the Earth & Lithosphere

The Earth is the largest of the rocky planets moving around the Sun by mass and by size. The Earth’s shape is a spheroid: not quite a sphere because it is slightly squashed on the top and bottom. The shape is called an oblate spheroid. As the Earth spins around itself, the centrifugal force forces the equator out a little and pulls the poles in a little making it a unique type of spheroid. As this shape is unique it is also called ‘geoid’ or Earth-like.
The deepest hole ever dug is only about 12.3 kilometres or 7.6 miles. Still, we know something about the inside of the Earth, because we can learn things from earthquakes and the volcano eruptions. We are able to see how quickly the shock waves move through the Earth in different places and determine the type of materials making up that area.
The interior of the Earth is divided into layers. These layers are both physically and chemically different. The Earth has an outer solid crust, a highly viscous mantle, a liquid outer core, and a solid inner core.
The boundaries between these layers were discovered by seismographs which showed the way vibrations bounced off the layers during earthquakes. Between the Earth’s crust and the mantle is a boundary called the moho. It was the first discovery of a major change in the Earth’s structure as one goes deeper.
The crust is the outermost layer of the Earth. It is made of solid rocks. It is mostly made of the lighter elements, silicon, oxygen, aluminium. Because of this, it is known as sial (silicon = Si; aluminium = Al) or felsic. The thickness of the crust varies under the oceanic and the continental areas. Oceanic crust is thinner as compared to the continental crust. The mean thickness of oceanic crust is 5 km whereas that of the continent is around 30 km. The continental crust is thicker in the areas of major mountain systems. It is as much as 70 km thick in the Himalayan region.
The mantle is the layer of the Earth right below the crust. It is made mostly of oxygen, silicon and the heavier element magnesium. It is known as siam (Si + am for magnesium) or mafic.The mantle extends from Moho’s discontinuity to a depth of 2,900 km. The mantle itself is divided into layers.
The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere(lithos=rock), an irregular layer with a maximum thickness of perhaps 200 km, of which the uppermost mantle is 120 to 50 km thick.
Below the lithosphere, the upper mantle becomes notably more plastic, called the asthenosphere, and is composed of flowing rock in the state of plasticity, about 200 km thick. It behaves as a hot viscous liquid and consists of hot, weak material that can be deformed like silly putty. That means it is capable of gradual flow. The lower mantle is much thicker than the upper mantle. It is made of magma, under great pressure, and so is thicker (higher viscosity) and flows less easily.
The Earth’s core is the part of Earth in the middle of our planet. It has a solid inner core and a liquid outer core.
The outer core of the Earth is a liquid layer about 2,260 kilometres thick. It is made of iron and nickel. This is above the Earth’s solid inner core and below the mantle. Its outer boundary is 2,890 km (1,800 mi) beneath the Earth’s surface. The transition between the inner core and outer core is approximately 5,150 km beneath the Earth’s surface.
The temperature of the outer core ranges from 4400 °C in the outer regions to 6100 °C near the inner core. The outer core is not under enough pressure to be solid, so it is liquid even though it’s mostly made of the same stuff as the inner core. Sulphur and oxygen could also be in the outer core.
The inner core of the Earth, as detected by seismology, is a solid sphere about 1,216 km (760 mi) in radius, or about 70% that of the Moon. It is believed to be an iron–nickel alloy and may have a temperature similar to the Sun’s surface, approximately 5778 K (5505 °C).

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