Major types of rocks and their characteristics

June 4, 2017September 8, 2024 by PSC Notes

They are aggregates or physical mixture of one or more minerals. Minerals on the other hand are made up of two or more elements in a definite ratio. They have a definite chemical composition. Crust is made up of more than 2000 minerals, but out of these, 6 are the most abundant and contribute the maximum to this uppermost part of the earth. These are feldspar, quartz, pyroxenes, amphiboles, mica and olivine.
Rocks are of immense economic importance to us.
Rocks differ in their properties, size of particles and mode of formation. On the basis of mode of formation rocks may be grouped into three types:
(a) Igneous
(b) Sedimentary and
(c) Metamorphic

Igneous Rocks

Igneous Rocks are formed by crystallization from a liquid, or magma. They include two types
Volcanic or extrusive igneous rocks form when the magma cools and crystallizes on the surface of the Earth
Intrusive or plutonic igneous rocks wherein the magma crystallizes at depth in the Earth.

Magma is a mixture of liquid rock, crystals, and gas. Characterized by a wide range of chemical compositions, with high temperature, and properties of a liquid.
On the basis of their mode of occurrence, igneous rocks can be classified as : extrusive or volcanic rocks and intrusive rocks.
(i) Extrusive igneous rocks are formed by cooling of lava on the earth’s surface. As lava cools very rapidly on coming out of the hot interior of the earth, the mineral crystals forming these rocks are very fine. These rocks are also called volcanic rocks. Gabbro and basalt are very common examples of such rocks. These rocks are found in volcanic areas. Deccan plateau’s regur soil in India is derived from lava.

(ii) Intrusive igneous rocks are formed when magma solidifies below the earth’s surface. The rate of cooling below the earth’ s surface is very slow which gives rise to formation of large crystals in the rocks. Deep seated intrusive rocks are termed as plutonic rocks and shallow depth intrusive rocks are termed as hypabyssal. Granite and dolerite are common examples of intru- sive rocks. From this point of view, therefore, igneous rocks can, in accor- dance with their mode of formation, be classified as (a) Plutonic, (b) Hyp- abyssal and (c) Volcanic rockmasses. The huge blocks of coarse granitic rocks are found both in the Himalaya and the Decean Plateau.

Sedimentary Rocks

Sedimentary rocks are formed by successive deposition of sediments. These sediments may be the debris eroded from any previously existing rock which may be igneous rock, metamorphic or old sedimentary rock. Sedimentary rocks have layered or stratified structure. The thickness of strata varies from few millimeters to several metres. So these rocks are also called stratified rocks. Generally, these rocks have some type of fossil between their strata. Fossil is the solid part or an impression of a prehistoric animal or plant embedded in strata of sedimentary rocks. Sedimentary rocks are widely spread on the earth surface but to a shallow depth.

The formation of sedimentary rocks involves five processes:

Weathering – The first step is transforming solid rock into smaller fragments or dissolved ions by physical and chemical weathering as discussed in the last lecture.
2. Erosion – Erosion is actually many process which act together to lower the surface of the earth. In terms of producing sediment, erosion begins the transpiration process by moving the weathered products from their original location. This can take place by gravity (mass wasting events like landslides or rock falls), by running water. by wind, or by moving ice. Erosion overlaps with transpiration.
3. Transportation – Sediment can be transported by sliding down slopes, being picked up by the wind, or by being carried by running water in streams, rivers, or ocean currents. The distance the sediment is transported and the energy of the transporting medium all leave clues in the final sediment that tell us something about the mode of transportation.
4. Deposition – Sediment is deposited when the energy of the transporting medium becomes too low to continue the transport process. In other words, if the velocity of the transporting medium becomes too low to transport sediment, the sediment will fall out and become deposited. The final sediment thus reflects the energy of the transporting medium.
5. Lithification (Diagenesis) – Lithification is the process that turns sediment into rock. The first stage of the process is compaction. Compaction occurs as the weight of the overlying material increases. Compaction forces the grains closer together, reducing pore space and eliminating some of the contained water. Some of this water may carry mineral components in solution, and these constituents may later precipitate as new minerals in the pore spaces. This causes cementation, which will then start to bind the individual .

Metamorphic Rocks

Metamorphic rocks are formed under the influence of heat or pressure on sedimentary or igneous rocks. Tremendous pressure and high temperature change the colour, hard- ness, structure and composition of all types of pre-existing rocks. The process which bring about the change is known as Metamorphism and the ultimate products, formed due to operation of such processes are defined as the Metamrphic rocks.
Metamorphism refers to the changes in mineral assemblage and texture that result from subjecting a rock to pressures and temperatures different from those under which the rock originally formed.
The original rock that has undergone metamorphism is called the protolith. Protolith can be any type of rock .

Metamorphism occurs because rocks undergo changes in temperature and pressure and may be subjected to differential stress and hydrothermal fluids. Metamorphism occurs because some minerals are stable only under certain conditions of pressure and temperature. When pressure and temperature change, chemical reactions occur to cause the minerals in the rock to change to an assemblage that is stable at the new pressure and temperature conditions. But, the process is complicated by such things as how the pressure is applied, the time over which the rock is subjected to the higher pressure and temperature, and whether or not there is a fluid phase present during metamorphism. Different types of metamorphic rocks are found all over the world. In India, marble is found in Rajasthan, Bihar and Madhya Pradesh, whereas slates are available in plenty in Orissa, Andhra Pradesh and Haryana. In Kangra and Kumaun regions ]of Himalaya, slates of different colours are found.

Sustainable and Inclusive Growth

March 20, 2016September 5, 2024 by rawan239

The term Sustainable growth became prominent after the World Conservation Strategy Presented in 1980 by the International Union for the Conservation of Nature and Natural Resources. Brundland Report(1987) define sustainable development as the a process which seek to meet the needs and aspirations of the present generation without compromising the ability of the future generation to meet their own demands.

Natural resources are limited and thus sustainable development promotes their judicious use and put emphasis on conservation and protection of environment.Global warming and Climate change has brought the issue of Sustainable development in prominence.

Inclusive Growth is economic growth that creates opportunity for all segments of the population and distributes the dividends of increased prosperity, both in monetary and non-monetary terms, fairly across society.Indian Plans after the independence were based on the downward infiltration theory, which failed to bring equitable growth to all the sections of the Indian society.

Approach paper of 11th five year plan talked about “Inclusive and more faster growth” through bridging divides by including those in growth process who were excluded. Divide between above and Below Poverty Line, between those with productive jobs and those who are unemployed or grossly unemployed is at alarming stage.

Liberalization and Privatization after 1990’s have brought the nation out of the hindu growth rate syndrome but the share of growth has not been equitably distributed amongst different sections of Indian Society.

Various dimensions of Inclusive growth are:-

economic
social
financial
environmental

Important issues that are needed to be addressed to achieve the inclusive growth are:-

Poverty
Unemployment
Rural Infrastructure
Financial Inclusion
Balanced regional development
Gender equality
Human Resource Development (Health, Education, Skill Development)
Basic Human Resources like sanitation, drinking water, housing etc.

Government has launched several programs and policies for Inclusive growth such as:-

MNREGA
Jan Dhan Yojna
Atal Pension Yojna
Skill India Mission
Deen Dayal Upadhyaya Gram Jyoti Yojana
Pradhan Mantri Suraksha Bima Yojana
Pradhan Mantri Jeevan Jyoti Bima Yojana
Sukanya Samridhi Yojana
Pradhan Mantri Garib Kalyan Yojana
Jan Aushadhi Yojana (JAY)
Nai Manzil Scheme for minority students
The Pradhan Mantri Awas Yojana (PMAY) or Housing for all by 2022

Physical factors: Terrain, topography, climate, and soil. which determine agriculture

October 15, 2015September 2, 2024 by rawan239

Physical Factors:

(a) Terrain, Topography, and Altitude

dependent on the geo-ecological conditions; terrain, topography, slope and altitude.
paddy cultivation requires leveled fields, tea plantations perform well in the undulating topography in which water does not remain standing.
Orchards of coconut are found at low altitudes, preferably closer to the sea level, while the apple orchards in the tropical and sub-tropical conditions perform well above 1500 metres above sea level.
Cultivation of crops is rarely done 3500 m above sea-level in the tropical and sub-tropical latitudes.
highly rarified air, low-pressure, low temperature, and shortage of oxygen at high altitudes are the serious impediments not only in the cultivation of crops, but also in keeping dairy cattle.
soils of high mountainous tracts are generally immature which are also less conducive for agriculture.
topographical features also affect the distribution of rainfall.
the windward side gets more rainfall than the leeward side.
Apart from altitude and aspects of slope, the nature of the surface also affects the agricultural activities.
gullied land is least conducive for cropping.
The Chambal ravines in Madhya Pradesh, Rajasthan, and Uttar Pradesh have put over thousands of hectares of good arable land out of agriculture.

(b) Climate

(1) Temperature:

The crops to be grown, their patterns and combinations controlled by the temperature and precipitation conditions.
each crop has a specific zero temperature below which it can not be grown.
also an optimal temperature in which the crop is at its greatest vigour.
For each stage of crop life, i.e. germination, foliation, blossoming or fructification a specific zero and optimum can be observed in temperature.
The upper limit of temperature for plants growth is 60°C under high temperature conditions, i.e. at over 40°C, crops dry up, if the moisture supply is inadequate.
In contrast to this, the chilling and freezing temperatures have a great adverse effect on the germination, growth and ripening of crops.
Crops like rice, sugarcane, jute, cotton, chilli and tomatoes are killed or damaged at the occurrence of frost.
minimum temperature for wheat and barley is 5°C, maize 10°C, and rice 20°C.
impact of temperature on cropping patterns may be seen from the fact that the northern limit of the regions in which date-palm bear ripe fruit coincides almost exactly with the mean annual temperature of 19°C.
essential factor in the limit of grape orchards seem to be temperature. Grapes ripen only in those countries in which the mean temperature from April to October exceeds 15° C.
Crops like winter-wheat and barley perform well when the mean daily temperature ranges between 15°C and 25°C.
tropical crops like cocoa, coffee, spices, squash, rubber and tobacco require over 18° C temperature even in the coldest months, while crops like wheat, gram, peas, lentil, potato, mustard, and rapeseed require a temperature of about 20°C during the growth and development, stage and relatively higher (over 25°C) during the sowing and harvesting periods.

(2) Moisture:

All crops need moisture.
Take water and moisture from the soil.
Available from the rains or from irrigation systems.
Within wide temperature limits, moisture is more important than any other climatic factor in crop production.
There are optimal moisture conditions for crop development just as there are optimal temperature conditions.
Excessive amount of water in the soil alters various chemical and biological processes, limiting the amount of oxygen and increasing the formation of compounds that are toxic to plant roots.
Excess of water in the soil, therefore, leads to stunted growth of plants.
The problem of inadequate oxygen in the soil can be solved by drainage practices in an ill-drained tract. Heavy rainfall may directly damage plants or interfere with flowering and pollination.
Cereal crops are often lodged by rain and this makes harvest difficult and promotes spoilage and diseases.
Heavy rainfall at the maturity of wheat, gram, millets, oilseeds, and mustards cause loss of grains and fodder.
Indian farmers all over the country have often suffered on account of failure of rains or fury of floods.

(3) Drought:

Devastating consequences on the crops, their yields and production.
Soil drought has been described as a condition in which the amount of water needed for transpiration and direct evaporation exceeds the amount of water available in the soil.
Damages the crops when plants are inadequately supplied with moisture from the soil.
drought prone areas of India lie in the states of Rajasthan, Gujarat, Madhya Pradesh, Chhattisgarh, Jharkhand, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, Orissa, Bundelkhand (U.P.), Uttarakhand, H.P.J&K, south-west Punjab and Haryana.
Where the average annual rainfall is less than 75 cm, agriculture is considered a gamble on monsoon.
The incidence of drought and its intensity can be determined from the annual, seasonal and diurnal distribution of rainfall.
drought prone areas of India, dry farming is practiced, while in the more rainfall recording regions, intensive agriculture of paddy crop is a common practice.

(4) Snow:

Occurrence of snow reduces the ground temperature which hinders the germination and growth of crops.
Land under snow cannot be prepared for sowing because of permafrost.
Melting of snow may cause hazardous floods in the summer season, affecting the crops, livestock, and land property adversely.

(5)Winds

Have both, direct and indirect effects on crops.
Direct winds result in the breaking of plant structure, dislodging of cereals, fodder and cash crops and shattering of seed-heads.
Fruit and nut crops may be stripped from the trees in high winds.
Small plants are sometimes completely covered by wind-blown dust or sand.
The indirect effect of winds are in the form of transport of moisture and heat in the air.

(c) Soils

Important determining physical factor.
Determines the cropping patterns, their associations and production.
Fertility of soil, its texture, structure and humus contents have a direct bearing on crops and their productivity.
The alluvial soils are considered to be good for wheat, barley, gram, oilseeds, pulses, and sugarcane; while the clayey loam gives good crop of rice.
Regur soil is known for cotton, and sandy soil for bajra, guar, pulses (green-gram, black-gram, red-gram, etc.).
The saline and alkaline soils are useless from the agricultural point of view unless they are reclaimed by chemical fertilisers and biological manures and fertilisers.

Climatic changes

June 4, 2017September 1, 2024 by PSC Notes

It is the long term change in the statistical distribution of weather patterns over periods of time
Though it has been happening naturally for millions of years, in recent years it has accelerated due to anthropogenic causes and has been causing global warming.
UNFCCC defines climate change as – “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”