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Saturday, 9 March 2019

All about India part 1: political and physical || Learners Hobby

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                                                         Location and extent- political
    Indian is almost in the center of the southern end of the Asian continent. India lies entirely in the Northern Hemisphere. The Tropic of Cancer divides the Indian landmass into two almost equal halves. Peninsular India, below the Tropic of Cancer, lies in the Tropical zone.

    India share its land boundaries with seven neighbouring countries. These countries are Pakistan and Afghanistan in the North-West; China, Nepal and Bhutan in the North; Bangladesh and Myanmar to the East. The Palk Strait separates India from Sri Lanka.
    India has 29 States and 7 Union Territories. For administrative purpose, these political divisions are subdivided into 604 districts. Rajasthan is the largest State and Goa is the smallest State in terms of area.
    The Indian Republic is governed by the Constitution. The constitution provided for division of powers between the Union and the States. The three wings of the government, both at the central and the state level are - the Executive, the Legislature and the Judiciary.
    India Standard Time (IST) is 5.30 hours ahead of UT (Universal Time). Sri Lanka uses the same Standard Meridian and its time is also same. Standard Time of Pakistan is half hour behind IST and that of Bangladesh half-hour ahead. Find out the reasons.
                                                                         India - Physical
    The physical shape of the surface of the earth is known as its relief. The landmass of India is divided on the basis of relief. The Himalayan Mountains are found in ranges. They branch out in different directions from Pamir Knot.
    Mountain ranges which are farther away from the Himalayas are known as Trans-Himalayan Ranges. The eastern ranges, separated from the main Himalayas, are known as Purvanchal or the Eastern Hills. The arc-shaped Himalayan range in India is about 2,500 km in length. Its width varies from 400 km in the west to about 150 km in the east.
    India together with four other countries is known as a sub-continent. It is because of diversity of relief and climate. These conditions are a characteristic of a continent.
    The North Indian plains extend from the Indus Plain in the west to Brahmaputra Valley in the east. It is about 2500 km long. Its width varies from 150 to 180 km. The Ganga-Brahmaputra Delta is the largest and the fastest growing delta in the world. It is a marshy area known as Sundarbans or 'Beautiful forest'. It is an area renowned for its Mangrove swamps.
    The Deccan Plateau in the south is subdivided into many smaller plateaus. Though of volcanic origin, the soil is of varied types. People also live here.

    The Rajasthan desert, west of Aravallis, is a fairly flat and low lying land, an extensive sandy plain merging in the west with the Sind desert of Pakistan. Sambhar Lake is the India's largest saltwater lake.
    Coastal Plain are generally flat. The west coast is narrower than the East Coast.
    Two hill ranges known as Ghats run parallel to both west coast and east coast. There are gaps known as passes within the hill ranges for access to sea coast.
    Two islands groups of India are Andaman and Nicobar Islands in the Bay of Bengal and Lakhadweep Islands in the Arabian sea.

Wednesday, 20 February 2019

Major Landforms of the Earth: Plains and Landforms and the People << Learners Hobby

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    A relatively flat or low lying land surface is called a plain. Plains are generally not more than 200 metres above mean sea level. Depending on how they are formed, plains may be level or have a rolling, wave-like surface, i.e., undulating. Plains are formed by deposition process of rivers, winds and glaciers and by uplift or emergence from the sea  like the Great Plains of USA.

    Types of plains are named after the mode of formation, for e.g. plains formed by wind deposition are called loess plains. The Loess Plain of China is one of the largest of its kind.

    The plains are generally productive as those formed by river sediments. The areas formed by the deposition of sediments are called floodplains. Such plains are known as alluvial plains. Alluvium means soil or sediments, hence, the termed 'alluvial soil/plains'. Emerged plains are also found near sea coasts and are called coastal plains. Plains are also made by the actions of glaciers and winds.

    A river has three main stages in its course. Rivers originating in mountains are in the youthful stage, they have their middle and mature stage in the plains. In the upper course, the flow of water may be rapid and many smaller rivers may join the main river. Such rivers are called tributaries.
    River Ganga and its  tributaries have formed the extensive Indo-Gangetic Plain of India, Pains of Nile of Egypt and Yangtzee Plains of China are examples of alluvial plains.
    In the mature stage in the plains, a river may face many obstructions. It results in deposition of sediments. Besides formation of landforms a river divides into many streams which may never join the main river again. Such streams are called distributaries. Together with main river, the distributaries may form many landforms like delta. Ganga-Brahmaputra delta is one of the largest delta in the world. Many rivers end their courses near the sea coast. This last stage of the river is known as its mouth.
    Plains are most useful for human habitation. Since its inception human settlements have taken place at the banks of rivers because of the availability of water and fertile soil. The deposition of alluvium and availability of water, makes these plains extremely fertile and ideal for human habitation and cultivation of crops. Indeed, the first civilizations of the world evolved along the river banks.
    Human beings are one of the major agents causing water pollution apart from using it in a wasteful manner. Water is important for sustaining life on the planet. It is our duty to make Earth a better place to live and we must take care of our great heritage - the rivers.

                                                                       LANDFORMS AND THE PEOPLE
    We make use of land and water in different ways. For example, people prefer to live in plains, hill and other mountainous areas. Life is very difficult in the hilly regions e.g. Arunachal Pradesh. People travel using Rope-Bridge.

    The geographic extent of India has remained the same for past 62 years whereas the population of human and their cattle has increased several-fold since then. A large proportion of land is occupied by mountains. From abundant resources like land, water and minerals we have moved towards scarcity due to their limited availability.

    We often put these limited resources like land and water to many wasteful uses. For example, houses are constructed on fertile land. Water and air are used in a careless manner. Further we often pollute these resources of land, water and air.

Monday, 18 February 2019

Major Landforms of the Earth: Mountains and Plateaus << Learner Hobby

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    The relief of India has been shaped by both internal and external forces operating in the earth. It is often on account of variations and inequalities in shapes and forms of mountains, basis of altitudes.
    The relief on the surface of the earth is shaped by internal and external processes described earlier.
    The internal processes lead to uplifting and sinking of the Earth's surface at plate margins. The process leads to earthquakes and volcanoes. The ground on which we stand is constantly on the move.
    The external processes wear down and rebuild the land surface. Weathering and erosion work on landforms over a long period of time to bring about a noticeable change. Weathering causes rocks to crack, crumble or degrade, which they do due to chemical, physical or biological interactions. The agents of erosion loosen and carry away rock debris formed by weathering. Rivers, winds, glaciers and moisture are the most powerful agents of weathering and erosion. The rebuilding process takes place through deposition by these very agents.
    It may be mentioned that internal processes rebuilding the uneven surface of the earth whereas external processes result in levelling off.
    The disintegration of rocks on account of atmospheric and other processes is known as weathering. It is of three types - physical, chemical and biological. For example, water flowing in rivers strikes against rocks on the bed and banks of rivers. It shatters the rock and causes its physical break up also known as mechanical weathering. IT is not pure water itself by sediments in the river that cause this action. Similarly, winds blow up sand and other particles, when they strike against the rocks. They produce cracks leading to disintegration.
Weathering as already stated is on account of weather, as such its effects on rocks can be of many types depending on the type of rock. It is best depicted by pictures below:


    A mountain is any natural elevation on the surface of the earth. The rise of the elevation in proportion to its base differs from region to region and place to place on the earth. Therefore, a uniform classification with respect to elevation of a hill differs from a mountain and so does plateau. A hill (610 m) is lower than a mountain (8000 m) but higher than plateau. Mountains like Himalayas and Andes are arranged in rows and hence are called Ranges.
    Based on the mode of formation, mountains are generally classified into three types-fold, block and volcanic. The fold mountains are subdivided into young fold and old fold mountains.  Mountains like the Himalayas which are still rising are called 'Young Fold Mountains'. They were formed when the Earth's crust folded because of its internal movements. This convergence took place millions of years ago and is still continuing. As a result Himalayas is still rising.
    Old mountain ranges like the Aravallis of India, and Urals of Russia are low in height and have rounded peaks. They are termed as old fold mountains because the process of mountain building has stopped and external processes have taken place.

    Block mountains are created when large areas of the Earth are fractured into huge blocks and displaced. The uplifted blocks are called Horsts and the lowered blocks are called Grabens.
    The Rhine valley and Vosges in Europe are examples of block mountains. In  these valleys like in the case of fold mountain range many rivers flow.
    The volcanic mountains are made by the solidification of lava on the surface of the Earth. After sometime, layers are accumulated to give rise to mountains Mountains such as Kilimanjaro in Africa and Fujiyama in Japan are volcanic mountains.
   Mountains are also found under the oceans. Andaman and Nicobar Islands are actually summits of mountains in the sea. Mauna Kea in the Pacific Ocean is an under-sea mountain. It is 1000m beneath the ocean's surface.

    Plateau is an elevated flat land. It is also called Tableland because it is flat-topped, have one or more sides with steep slopes. The elevation may differ according to general elevation may differ according to general elevation of the land. In the American continent, an elevation of 6000 m above sea level may be termed as a mountain. But in Asia some plateaus are even above this height generally the plateaus are made by internal processes alongside mountains. Some plateaus are even made by solidfication of lava or by external processes.
    Based on the mode of formation, Plateaus are of different types like Basalt Plateau and Plateau Gravel. However two types of plateaus need to be distinguished as given below:
    Piedmont:  A plateau at the foot of a mountain is termed as a piedmont plateau. Plateaus are generally found near the mountain but some may even exist separately e.g. in the American continent and N.W. Italy.
    Intermontane: Intermontane refers to any features lying between two mountain or mountain ranges. The Plateau of Tibet, north of Himalayas, is the fine example intermontane plateau. It is known as the 'Roof of the World'. There are also similar plateaus between the east and west ranges of Andes mountains.
    Plateaus are the richest mining areas. Plateaus also have fertile soils. Examples include the Chhotanagpur Plateau in India and the African Plateau, which is famous for gold and diamond deposits. Waterfalls are also found in plateau areas.
    In the Chhotanagpur Plateau, Hundru falls on river Subernarekha adds to the exquisite beauty of the region.
    Jog falls in Karnataka is the highest waterfall in India. All these are a part of a whole tableland known as the Deccan Plateau.
    India has many large rivers. The northern rivers originate from glaciers in the Himalayas and flow throughout the year. The rivers of South India depend on rainfall and flow during parts of the year. All the rivers usually have their mouth near the sea and make beautiful valleys in the upper course.

Saturday, 16 February 2019

States of Matter << Learners Hobby

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Anything which occupies space and has mass is matter. And that matter is made of tiny particles called atoms. These atoms combine or cling together to form molecules. How matter behaves under different conditions depends on how atoms group together to form molecules and how molecules are arranged. In other words, the  behaviour of matter depends on its structure. In this chapter, we will study the structure of matter in its three states and how matter changes from one state to another.
    There are two things you must know about molecules before we take a closer look at solids, liquids and gases.
    First, the molecules of matter attract each other. The force of attraction between molecules is called intermolecular force. The strength of this force depends upon the distance between the molecules. The closer the molecules, the greater is the intermolecular force. This force tries to keep the molecules together.
    Second, the molecules of matter are in constant motion. They are, however, kept in place by the force of attraction between them. When the energy of molecules increases (say, because of an increase in temperature), their motion also increases. When they gain enough energy, they can overcome the intermolecular force of attraction and move away from each other.
    The state (solid, liquid or gaseous) of a substance under particular conditions depends upon which factor has a greater effect - intermolecular force or molecular motion. We say 'under particular conditions' because most substance can exist in all three states. We think of nitrogen as a gas or kerosene as a liquid or iron as a solid because these substances exist in these states under the conditions of temperature and pressure existing on the earth. They could exist in other states if we changed the temperature and pressure.

In a solid, the molecules are arranged very close to each other, so the intermolecular force is strong. This makes it practically impossible for them to get away from each other, just as you cannot get away from your partner in a three-legged race because his leg is tied to yours. Imagine rows and rows of people with their legs tied together. They might be able to jump about a little, but if they really want to move, they will have to move together, keeping their 'arrangement' intact. Similarly, the arrangement of molecules in a solid remains intact. In other words, the molecules of a solid are arranged in a regular pattern. They cannot slip past each other, so a solid does not flow.
    It is not as if the molecules of a solid do not move at all. However, they cannot move much, just as mothballs packed tightly in a carton cannot move much. And just like a carton of mothballs packed tightly together, a solid has a definite shape and size. You cannot really squash a box of mothballs out of shape because the mothballs have nowhere to move. Similarly, the closely packed molecules of a solid cannot move much, so a solid is generally hard, rigid and cannot be compressed.
Porous solids: There are some exception, however. You can, for example, squeeze a sponge or compress it. This is because it has millions of little holes, or pores, which are filled up with air. When you squeeze the sponge, the air gets forced out. If you squeeze it under water, you will see the air bubbling out of it. Under water, the pores in a sponge get filled with water. If you take the sponge out of the water and squeeze it again, the water flows out of the pores.
    A solid which has pores is called porous. The porosity of some solids is a great blessing for us. It is because paper is pores that ink leaves a mark on it. The pores in paper hold the ink, which would otherwise have go wiped off. The pores in woollen clothes trap air and keep us warm. The pores in the soil hold water, which is drawn by the roots of plants. Water seeps out of the pores of earthen pots and evaporates. Evaporation, if you remember, is a change that requires energy. This energy comes from the water in the pot and the water cools.
    The molecules of a liquid are much farther apart than those in a solid. Thus, the intermolecular force holding them together is weaker, and they can move about more freely and faster than the molecules of a solid. This lets them slip past each other, allowing the liquid to flow and take on the shape of any container it is poured into. The molecules of a liquid are not held together in a regular pattern. However, intermolecular force does bind them to some extent, so they cannot get away from each other altogether. This is why a liquid has a definite volume, though it is free to flow and does not have a particular shape. You can pour 200 ml of water into a jug, a beaker or a pan. It will take on the shape of the container, but its volume will remain the same (200 ml).
    Gas molecules are so far apart that the forces between them are very weak. So weak are these forces that the molecules are quite independent and can move about freely in all directions. They move much faster than liquid molecules, and fill up all the space available to them in almost no time. That is why when someone lights an incense stick at one end of a big room, the fragrance spreads all over the room very rapidly. Since gas molecules move about freely, a gas has no particular shape of volume.
    The movement of solid particles caused by collisions with the constantly moving molecules of a gas (or liquid) is called Brownian movement, after the botanist Robert Brown. He observed the motion of pollen grains in a liquid.
    The large spaces between gas molecules make gases compressible. Of course, you have to apply some pressure in order to compress a gas. You do this when you pump air into a bicycle tube. The gas in an LPG cylinder is also compressed and confined to the volume of the cylinder under great pressure. When a cylinder leaks, the gas is no longer under pressure and it spreads all over the kitchen.
    There is another way in which gases differ from solids and liquids. They do not have a surface. Solid molecules are held together very tightly. So, solids have shapes, sizes and clearly defined surfaces. Liquid molecules are not held so tightly. Still, the forces of attraction are strong enough to pull the molecules into the liquid. This is why liquids also have surfaces. Gas molecules are so independent of each other and so free to move about that gases do not have surfaces.

Friday, 15 February 2019

Elements And Compounds << Learners Hobby

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The fact that matter can be classified into elements. compounds and mixtures is not new to you. This classification is based on what matter is made up of. Elements and compounds are made up of one kind of particle - either atoms or molecules. Mixture. on the other hand, contain more than one kind of particle, since they are composed of two or more elements or compounds mixed up loosely. We call elements and compounds pure substances because their composition is always fixed. This is not true of mixture. A mixture of salt and sugar, for example, can contain the two substances in any proportion. If you mix 100 gm of sugar and 100 gm of salt, it will be a salt-and-sugar mixture, and if you mix 100 gm of sugar and 50 gm of salt, it will still be a salt-and-sugar mixture.
    All matter is made up of elements. There are more than 114 elements, of which 92 occur in nature. The rest have been synthesised (made) by man. Iron, copper, hydrogen and oxygen are all elements.
    The smallest particle of an element is an atom. An element is a pure substance that cannot be broken up into simpler substances and contains only one king of atom. Different elements are made up of different kinds of atoms. But all the atoms in one element are identical. For instance, hydrogen contains hydrogen atoms, which are all identical. Oxygen contains oxygen atoms, which are identical. But hydrogen atoms are different from oxygen atoms. It is the kind of atom an element contains that determines its properties. The atoms of hydrogen are very different from those of oxygen, so hydrogen and oxygen behave differently, or have different properties.
    Though the atom is the smallest particle of an element, the atoms of many elements cannot exist on their own. They need to link with other atoms to form molecules. An oxygen atom, for example, cannot exist on its own. It pairs up with another atom to form an oxygen molecule. Mind you, an oxygen atom is still the most basic particle of oxygen-it has all the properties characteristic of oxygen. Also, it is the atom of an element which takes part in a reaction. That is how a water molecule is made up of two hydrogen atoms and one oxygen atom. If only a molecule of oxygen could take part in a reaction, this would not have been so. We can now say the following about atoms and molecules.
    An atom is the smallest particle of an element. It is not always capable of existing independently. It takes part in a chemical reaction.
    A molecule is the smallest particle is an element or a compound that can exist independently.
    The atomicity of an element is the number of atoms contained in a molecule of the element. The automicity of oxygen is two, while that of phosphorus is four. The atoms of some elements can exist independently, for example, helium, gold and silver.
    A compound is a pure substance formed by the chemical combination of two or more elements in a fixed proportion. Common salt and water are two compounds that we use every day.
    Let us now see what exactly the definition of a compound means. The  smallest particle of a compound, as you already know, is a molecule. Every molecule of a compound is identical. Each contains the same number of atoms of the elements which constitute the compound. In other words, the composition of a compound is always the same, no matter how you prepare it. That is why we call a compound a pure substance. We could also say that a compound always contains the same elements chemically combined in the same ratio. A molecule of water will always contain two atoms of hydrogen and one atom of oxygen. Do you now see why we say that a compound is formed by the chemical combination of elements in a 'fixed proportion? And we specify 'chemical combination'  because just mixing together two elements does not form a compound.

    A compound, like an element, is a pure substance. However, an element cannot be broken down into simpler substances, while a compound can be broken down into the elements it is made up of. Remember though, that chemical processes have to be used to break down a compound. You cannot use physical methods to separate the elements that form a compound. For example, you cannot break down water into oxygen and hydrogen, unless you pass an electric current though it.

    A compound is made up of elements. However, the properties of a compound are very different from those of the elements that constitute it. This is because the atoms of the constituent elements combine, or link up together, to form different molecules, and the properties of a substance, as you know, depend on the kind of molecules it contains. Salt, for instance, is a white, crystalline solid formed by sodium and chlorine. But sodium is a soft, yellow metal, while chlorine is a greenish yellow gas with a choking smell.

Monday, 11 February 2019

Major Domains of the Earth Part 2. << Learners Hoby

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                                    COMPARATIVE SIZES OF THE CONTINENTS
The Earth's landmass is divided into seven main continent and number of island. The greater part of the land areas lies in the Northern Hemisphere. The lad in the Southern Hemisphere lies close to the Equator. Thus, more than 95 % of total land areas occupied by continents is diametrically opposite to water bodies or oceans. This is known as antipodal arrangement of continents and oceans.
    The relative shapes of the continents are given below:
    Asia, occupying a little less than one-third of the Earth's total land area, is the world's largest continent. Africa is the second-largest continent.. It is the only continent through which the Tropic of Cancer, Equator and Tropic of Capricorn pass. Previously, it was known as the Dark Continent. The Sahara Desert, the world's largest desert is located in Africa.
    North America, world's third-largest continent, is connected to South America, world's fourth-largest continent, by the Isthmus of Panama.
    Antarctica is the fifth-largest continent of the world. Since the continent remains frozen at all times of the year, it is called the White Continent.
    Europe, the second-smallest continent, is separated from Asia by the Urals, the Caucasus mountains. Europe and Asia together are known as Eurasia.
    Australia is the smalls island-continent between the Pacific Ocean and the Indian Ocean and lies entirely in the Southern Hemisphere. It is the only continent comprising of a single country. It is about twice the size of India but its population is thirty-five times less than that of India.
    Oceans are a part of hydrosphere.
    The large water bodies surrounding the continents are  called Oceans. the four main oceans are as:
1. The Pacific Ocean
2. The Atlantic Ocean
3. The Indian Ocean
4. The Arctic Ocean.
                                                   OCEAN-LAND INTERFACE
    Spectacular landforms are often found where oceans and land meet. Some of these landforms are Seas, Islands, Peninsula, Strait and Isthmus.
    A stretch of land surrounded by ocean water on all sides is called an island. The best examples of islands are Sri Lanka and Australia (the latter is also a continent). The Andaman and Nicobar and Lakshadweep groups of islands are other examples.
    Peninsula is a landmass that, though connected to the mainland, juts out into the sea. It is surrounded by sea on three sides. India is the best example of a peninsular country.
    An Isthmus is a narrow strip of land linking two large landmasses and separating the seas on either side. The Suez Canal is built on the Isthmus of Suez. It separates Africa from Asia. The panama Canal, linking North America and South America, is built on the Isthmus of Panama.

    Delta, estuary, cliff and beaches are also some of the more striking landforms. A delta is formed near the mouth of a river where the sea is relatively calm. The Ganga-Brahmaputra Delta is the largest in the world.
    There are two types of seas-
1. linked to the main ocean like Arabian Sea, and
2. Inland Sea that has no outlet to the main ocean. Caspian Sea is an example of inland sea.
    A strait is a narrow passage of water connecting two large water bodies and separating two large landmasses. For example, the Palk Strait is a stretch of water separating India and  Sri Lanka.
    The oceans and winds also shape many landforms on the sea coasts. Chief among these are indented coastlines like the coastlines of Dublin and Belfast in the Atlantic Ocean.
    Of all the water on Earth, 97.2% is in oceans. The water that falls on the earth's surface through precipitation is termed as fresh water. It accounts for only 2.8% of total water on earth. Of this, the water stored in ice-sheets, glaciers and underground water accounts for 2.77%. The fresh water that flows in rivers and lakes account for only 0.03%. It is this water that we use for drinking, irrigation household and industrial purposes.

Sunday, 10 February 2019

Major Domains of the Earth Part 1 << Learners Hobby

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    Continents and oceans are the two main divisions of the Earth's surface. Three-fourths of the Earth's surface is covered by water in the for of oceans, seas, lakes and rivers. The three realms of the earth are:
1. Lithosphere (land) : The Lithosphere comprises the rocks of the Earth's crust and thin layer of soil that contains life sustaining nutrients.
2. Hydrosphere (water) : The Earth's hydrosphere consists of water available i various water bodies such as oceans, seas, rivers, lakes, underground water, glaciers, snow or as water vapour. All the oceans of the world are connected. They are separated and linked by continents.
3. Atmosphere (air) : The atmosphere provides life sustaining gases like oxygen and nitrogen. Plants do not use nitrogen directly from the atmosphere; their roots absorb it from the soil. This is just one example of interaction and inter-dependence of these domains.
Biosphere (life) : Biosphere represents life on Earth, be it in water, on soil, under the soil or in the air. The narrow zone of contact between land, air and water is called biosphere. In recent years, the biosphere together with its physical environment has also been termed as Ecosphere. The ecosphere, though actually biosphere., shows some ecological factors like climate and vegetation which influence the biosphere.
    The three realms and the biosphere establish and inter-relationship and are interdependent on each other in the ecosphere. The give-and-take relationship between the realms goes on endlessly.

    Various processes like weathering, nitrogen cycle, etc., take place  because of their interaction. It also sometimes leads to the formation of spectacular landforms. Of these processes the forces acting in the interior of the Earth produce first degree landforms like mountains and plateaus, explained subsequently.
    The interior of the Earth has three chief layer known as the crust, the mantle and the core. The continents and oceans rest on the crust. The mantle is the thickest of all layers. The lower mantle remains in a semi-molten condition. The molten rocks with gases and steam known as magma moves and finds its way up through cracks and fissures in rocks. The magma generates convection currents in the interior of the Earth. These currents have broken the earth's crust into small blocks, called plates. The movements of these plates as well as magma has produced fold mountains like Himalayas and Andes. The molten material when driven out on the surface is called lava. Many landforms, especially volcanic mountains, are made up of layers of lava. Below the mantle, lies the core. The core is composed of 80% iron along with some percentage of nickel and other light elements.
    The external forces are a result of a climate and interaction of its components - temperature and wind. These external forces are - weathering and erosion together known as denudation. Whereas changes like raising and lowering of landforms is always sudden. The changes on account of external forces are always aimed at lowering of these landforms.

Millions of years ago, there was only one super-continent called Pangaea and one super-ocean called Panthalassa. On account of buoyancy and convection currents rising from semi-molten rocks under the lithosphere, the continent keeps moving. Cue to geological changes over several million years, the sole continent split into many small and big rocks of land called plates.
    The evolution of continents and oceans is a continuous process as a result of movements of plates in different directions. The forces responsible for the movement of plates are :
1. Extremely hot interior of the earth which melts the rock and gives rise to movements of plates.
2. The forces of buoyancy of ocean water provides additional momentum to oceanic plates in a similar manner as happens to a boat.

    The parts of lithosphere are not only affected by movements indifferent directions but also by their emergence or submergence in and out of water in oceans. The process of evolution of Earth's land masses is based on certain events. Presently, the earth is divided into 7 major continents and 4 large oceans.
    Change is the property of nature. The present configuration will change in future gradually. The future earth 50 millions years hence is depicted. As per the current geological studies, large parts of the Earth will sink below the present sea level. The levels of some parts of the present oceans will fall and land will be exposed as landmasses. The Pacific Ocean will become smaller in size and the Atlantic will become large. The Australian continent will move closer to the equator. In this way, the dynamic Earth maintains the balance of its crust.