Rajasthan Board RBSE Class 11 Geography Notes Chapter 10 Agents of Erosion

→ Internal and external forces create various topographies on the earth’s surface.

→ External forces perform the work of denudation of rocks by the activities of weathering, erosion and mass translocation.

→ Erosion is a dynamic process. Forces such as rivers, oceanic waves, winds, glaciers and underground water which participate in erosion are known as the factors of erosion.

→ Climate, situation, structure and composition of rocks are the factors which affect erosion.

→ Erosive and depositional activities play an important role in the formation of various topographies on the surface of the earth.

→ Activities of erosion and deposition are mainly visible in the form of river or fluvial topographies, oceanic waves or coastal topographies, wind or arid topographies, glaciers or glacial topographies and underground water or Karst topographies.

River-Fluvial Topographies

• Due to increasing water, erosion takes place in the background, and in the bottom and deposition of the eroded debris also takes place. Two types of topographies are formed due to this: erosional topography and depositional topography.
• Gorges, canyons, waterfalls, rapids, potholes, structural terrace, river meanders and peneplanes are among the major topographies which are formed by erosion.
• Alluvial cones, alluvial fan, delta, natural levees, flood plains and oxbow-lakes are the major among depositional topographies.

Sea Waves-Coastal Topographies

• Ripples which emerge upon the surface of the sea due to the blowing of winds are known as waves.
• Waves perform the activities of hydrolysis, corrasion, attrition and hydraulic pressure due to which, erosional topographies are formed through erosion and depositional topographies are formed through the deposit of debris.
• Cliffs, caves, sea caves, blowouts, natural arch, stacks, wave cot platforms, etc. are included in erosional topographies.
• Beaches, cusp beaches, spits, bars, offshore bars, hooks, loops, connecting bars, lagoons and bay bars and tumbolo, etc. are included in depositional topographies.

Wind-Arid Topographies

• Topographies which are formed in desert regions due to the result of blowing of winds are known as wind-born or arid topographies.
• Winds perform transportation, corrasion, attrition in desert regions and cut, erode and transport the rock particles of rocks and perform their deposition at other places.
• Two types of topographies are formed through winds in desert regions: erosional topographies and depositional topographies.
• Blow outs, inselberge, mushroom rocks, demoiselles, driekanter, stone lattice, zeugen/zeujen, yardang, etc. are included in erosional topographies.
• Sand dunes, ripples, sand drifts, sand levees and loess are included in depositional topographies.

Glacial Topographies

• Glaciers gradually shift from their place of agglomeration on the surface.
• In glaciated regions, glaciers perform weathering of rocks through plucking, repulsion and attrition and deposit the moraines in various forms.
• Various erosional and depositional topographies are formed in glacial regions.
• U-shaped valleys, hanging valleys, glacial tarns, nunataks, cols, crags and tails, sheep rocks and fjord are included in erosional topographies.
• Moraines, eskers, kames, kettles, drumlins and glacial precipitant valleys are included in depositional topographies.

Ground-Water-Karst Topographies

• Water situated in holes and cracks of underground rocks present below the earth’s surface is known as groundwater.
• In regions of limestone rocks, groundwater forms various landforms above and below the surface of groundwater through the process of oxidation.
• Region of lime is known as karst region. The term ‘karst region’ has originated from the Yugoslavian word ‘krass region’. On the basis of this name, topographies formed in limestone regions in all the countries of the world are known as karst topographies.
• Two types of topographies are present in lime regions: erosional topographies and depositional topographies.
• Tera-Rossa, lapies, sink-holes, swallow holes, dolines, uvalas, polijes, sinking creeks and blind valleys are included in erosional topographies.
• Stalactites, stalagmites, cave pillars, dripstones and nodules are included in depositional topographies.

Agents of Erosion Notes Important Terms

→ Denudation: Depletion of layers of rocks or land erosion caused by physical factors, which includes weathering, erosion and mass translocation.

→ Fluvial Topographies: Flowing water rakes and scrapes the background of the water valley, separates the rocky material, transports it along and deposits it at another place. Topographies which are formed through this process are known as fluvial topographies.

→ Coastal Topographies: Topographies which are formed by erosion and deposition caused by sea waves are known as coastal or tidal waves-born topographies.

→ Arid Topographies: The erosional and depositional activities caused by blowing winds in arid regions form various topographies. Such topographies are known as arid or wind-born topographies.

→ Glaciated Topographies: In glaciated regions, glaciers perform erosion of rocks by evulsion, corrasion and attrition and deposit the moraines in various forms due to which various erosional and depositional topographies are formed in glaciated regions. Such topographies are known as glaciated or glacial topographies.

→ Karst Topographies: In limestone regions, underground water forms various types of topographies above and below its surface through the process of oxidation. Lime topographies are known as karst topographies.

→ Estuary: The submerged mouth of the river, where conjunction of water coming from surface and saline water takes place, is known as estuary.

→ Gorge: A narrow valley between hills or mountains, typically with steep rocky walls and a stream running through it.

→ Canyon: Canyon is a comparatively narrower and deeper valley than a gorge which has edges with vertical slope.

→ River Meanders: These are excessively circuitous turns of the river, where the river flows like a snake.

→ Peneplain: Shapeless lowland plain formed in an arid climate region during the final stage of the erosion cycle in which residue of solid rocks are exceptionally found here and there in the form of dunes.

→ Alluvial Cone: This refers to the deposit of debris in the shape of cone on the mountainous slope as the river enters into the plains from the mountains.

→ Natural Levees: These are walls of sandy soil formed on both sides of the river due to less water level.

→ Attrition: The process of mutual friction and breaking down of rock particles or rock segments flowing along with wind, water and glaciers, due to which the size of rock particles becomes smaller than before.

→ Sea Caves: Due to continuous erosion of gorges formed by waves in coastal regions, oceanic caves are formed. These are also known as oceanic caves.

→ Blow-out: Tidal waves form holes on the ceilings of coastal caves which are known as blow-outs.

→ Stack/Cave pillar: Pillar which is formed due to the breaking down of the ceiling of a natural arch is known as cave pillar or stack.

→ Wave Cat Platform: This is just like platforms built due to the cliff continuously shifting backward. Due to this, platform or leveled plain with gradual slope and bare rocks is formed in the sea in front of the cave. It is known as wave cat platform or plain.

→ Beach: Beaches are formed due to deposit rocks debris by the waves on the edges of the seashore.

→ Cusp Beach: Triangular beach formed from pebbles, stones, boulders, etc. which extends vertically towards the sea is known as cusp beach.

→ Spit: Deposit made by waves in the form of tongue towards the sea is known as spit. It is formed from the material deposited by offshore flow which takes the form of offshore bars.

→ Bars: Ridges or dams formed from deposition performed by waves are known as bars. This is parallel to the shore and usually at the time of high tide, oceanic water crosses the bar and reaches the shore.

→ Connecting Bars: Dam, ridge or wall which joins two islands are known as connectors or connecting bars.

→ Tumbolo: Bars which connect the islands with the shore are known as tumbolos.

→ Blow out: Those troughs which are formed by loose and disorganized terrain or rock parts blown and carried away by the wind are known as blowouts.

→ Inselberge: These are projected dunes of solid rocks in the desert-like large seas, and they appear to be like an island or a mountain.

→ Demoisells: Those surface columns in deserts which are protected with cover of solid rocks or terrain are known as demoisells.

→ Driekanter: A Dreikanter is a type of ventifact that typically forms in desert or periglacial environments due to the abrasive action of blowing wind.

→ Stone Lattice: This is a reticulated rock which is formed by the process of corrasion by the wind upon rocks with different compositions.

→ Zeugen: These are holes formed by erosion of wind in the layers of solid and gentle rocks spread alternately in horizontal form.

→ Yardang: These are pointed earth-shaped structures formed by respective vertical layers of hard and soft rocks.

→ Ripples: These are landforms which emerge on sandy surface of the desert just like oceanic waves.

→ Sand Drift: These are vertically moving guilds of sand, situated on the edge of topographical obstruction.

→ Sand Levees: These are vertical guilds of sand with a broad peak.

→ Loess: Deposit of very fine dust particles brought by blowing wind is known as loess. Their deposition takes place in places far away from deserts. Loess is usually yellow in colour.

→ Tarn: This is a lake formed by water getting filled up in cirque basin. Due to erosion of glacial valley, a small trough is formed at the bottom of the cirque basin. When the glacier melts, this trough gets filled up with water. This is generally known as tarn.

→ Nunatak: Projected dunes situated in glacial regions are known as nunatak. This is like an island in the middle of glacial cover. Nunatak usually develops in Antarctica continent and Greenland.

→ Gol: This is a traverse path formed by the conjunction of two adjacent cirques. Winds blow in different directions on the edges of the col and anti-synclines and depression, but winds are slow and discrete in the inner part of col.

→ Crag and Tail: A rocky outcrop with a tapering ridge of glacial deposits extending to one side.

→ Sheep Rock: This is a glacial rock or stone which resembles the shape of the back of sheep. Its slope which is in front of the glacier is gradual and its slope on the back is steep. These are also known as sheep-back shaped rocks.

→ Fjord: These are eroded coasts formed by submergence of glacial valleys. This is a landform which is deep, long, narrow and has steep slope.

→ Moraines: Deposits of pebbles, stones and boulders deposited by glaciers. These are situated on the edges, back and bottom of the glacier.

→ Esker: These are long, narrow and wavy ridges or dams formed by the deposit of glacial alluvium.

→ Kame: These are dunes which have steep slopes and are formed by glacial alluvium. They are formed by deposit of sand and gravel on abjection plains formed by glaciers.

→ Kettle: These are troughs which are formed by the melting of glaciers. These are small troughs formed in glacial plains.

→ Drumlin: Egg-basket shaped structure formed from the deposition of boulder bodies. Axis of drumlin is parallel to the direction of flow of the glacier. Drumlins are found on a large land part of Northern Ireland, Northern England and Northern United States of America.

→ Tera-Rossa: Red and brown soils formed by the process of oxidation are known as Tera-Rossa.

→ Lapies: These are pointed and thorny topographies which resemble lake beds.

→ Sink-Hole: These are troughs formed by the process of oxidation of water containing carbon dioxide. Swallow holes and dolines are also the same type of troughs, but they are comparatively larger in size.

→ Swallow-Hole: These holes are bigger in size as compared to sink holes.

→ Doline: Holes that are bigger in size or shape are known as dolines. Dolines usually originate due to expansion of swallow holes.

→ Uvala: These are expansive troughs formed by the mutual conjunction of various dolines. Uvalas usually have steep slopes and deposit of alluvium is found at their bottom.

→ Polije: These are expansive and larger-sized troughs formed by the conjunction of many uvalas. They are more extended than dolines and their walls are usually vertical.

→ Sinking Creek: Innumerable holes or pores on the edge of lime, from where water appears to be sinking are known as sinking creeks.

→ Stalagmite: This is a pillar-shaped structure formed on the ground of the cave. It is formed by the water dripping on the ground. Height of these pillars continues to increase due to progressive deposition.

→ Cave Pillar: This is a pillar-shaped structure formed by the conjunction of stalactite and stalagmite.

→ Drip-Stone: This is a lime pillar which resembles a curtain. It is situated at the bottom of the cave.

→ Nodules: Deposit of a type of mineral oil derived from rock holes is known as nodules.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 9 Denudation

→ The nature of landforms keeps on changing. Endogenetic forces build uneven landforms on the earth’s crust, while exogenetic forces always remain active in levelling them.

→ The process by which the cover of rocks of the crust gets eroded and removed, is called Denudation.

→ Weathering, erosion and mass translocation are included in denudation.

Weathering

• The breaking down of rocks by disintegration and decomposition at their own place by physical and chemical actions is called Weathering.
• Weathering is affected by the structure and organization of rock, slope of land, diversity in climate and vegetation.

Types of Weathering

• On the basis of the factors of disintegration and decomposition, weathering is classified into the following types: physical weathering, chemical weathering and biological weathering.
• Disintegration of rocks by insolation, frost, water and air pressure is called Physical Weathering.
• Change of rocks into new. compounds by the action of water and gases in a chemical process is called Chemical Weathering.
• Disintegration and decomposition occurring due to living-organisms found on the earth’s surface is called Biological Weathering.

Physical Weathering

• Physical weathering is classified in the form of Block Disintegration, Exfoliation, Frost Weathering and Pressure Release.
• Block Disintegration means disintegration of rocks into pieces, Exfoliation means breaking of rocks in form of shells, Frost Weathering means fragmentation by freezing and melting of snow, Pressure Release means cracks appearing in the rocks by upper pressure.

Chemical Weathering

• Chemical weathering is classified in the form of Oxidation, Carbonation, Desilication, Hydration and Dissolution.
• Oxidation means oxygen changing into oxides, Carbonation means carbon-dioxide dissolving in water to give carbonic acid, Desilication means separation of silica from rocks, Hydration means absorption of water by rock minerals, Dissolution means dissolving of substances in water.

Biological Weathering

• Biological weathering is classified in the form of weathering by vegetation, weathering by animals and weathering by humans.
• Weathering by vegetation means breaking of rocks by trees, Weathering by animals means disintegration of rocks by animals, Weathering by humans means fragmentation due to various human activities.

Erosion

• The word Erosion is made from the Latin word ‘Erodere’, the meaning of which is to rub or to nibble.
• Erosion is a dynamic process in which rocks keep on disintegrating by being rubbed, eroded, translocated or transported through glaciers, underground water, waves, air and rivers.
• The process of erosion takes place due to corrosion, attrition, hydraulic action, corrosion, deflation, cavitation and plucking.
• Eroded materials flow in three forms- dissolving, suspension and sliding.
• Deposition is the process of accumulation of the flowing debris, when the speed slows down or the slope becomes gentle after the erosion.

Mass Translocation

• Movement and transfer of rock debris in massive amount along the slope by gravitational force is called Mass Translocation.
• Creeping down from the slopes, the rock particles accumulate in the foothills. This accumulation or pile of rocks-flour is called Talus.
• A cone-shaped accumulation of loose rocks is called Talus Cone.

Differentiation of Mass Translocation

• Mass Translocation is classified in the form of gradual flow, rapid flow and extreme rapid flow.
• Earth Creep, Rock Creep, Talus Creep and Soil Creep are the forms of gradual flow.
• Earth flow, Mudflow and Sheet flow are the forms of rapid flow.
• Landslide, Rock Slide, Rock Fall, Landslip, Debris Fall and Slumping are the forms of extreme rapid flow.

Cycle of Erosion

• The concept of Cycle of Erosion was propounded by William Morris Davis in 1899.
• Landscape is regarded as the result of structure, process and stage by Davis.
• Period of stages is based upon the mobility of process and rock structure.
• Davis classified the cycle of erosion into the form of youth stage, mature stage and old stage.
• Davis called the flat plain part formed after the process of erosion as Pedeplain.

Penck’s Cycle of Erosion

• Walter Penck considered the cycle of erosion as the sum of the stages of development of landscapes, their uplift rate and inter-relations of their degradation.
• Penck classified the cycle of erosion into three time periods: Aufstegende, Gleighformige and Abstegende.

Denudation Notes Important Terms

→ Denudation: The physical process of stripping off the covering or removing the surface of rocks and land, in which weathering, erosion and mass translocation are included.

→ Endogenetic Force: Force originated from the internal part of earth due to which horizontal and vertical movements occur in the earth.

→ Exogenetic Force: Force originating or working on the surface of earth which is always active in levelling the earth’s surface.

→ Disintegration: The process of breaking down or splitting of rocks into the pieces by physical processes is called disintegration.

→ Decomposition: The process of decay of the rocks by dissolving as a result of corrosion of component minerals by chemical actions. In other words, decomposition is the process by which organic substances are broken into simpler matter.

→ Chemical Weathering: A process of weathering under which decomposition begins in the rocks due to chemical changes. By this, erosion of rocks takes place, which is called Chemical Weathering. Chemical weathering occurs mainly in the form of oxidation, carboniation and hydration.

→ Mechanical Weathering: The process of disintegration in the rocks due to physical factors like insolation, frost, air etc.

→ Humid tropics: The tropical regions where high temperature and high humidity are found in most duration of the year are called Humid tropics.

→ Insolation: Radiation energy received by the earth or other planets from the sun is called Insolation.

→ Frost: A deposit of small white ice crystals formed on the ground or other surfaces when the temperature falls below freezing point.

→ Block Disintegration: In hot, desert regions, cracks occur in the rocks due to daily extreme range of temperature. Over the passage of time, these rocks disintegrate into large pieces. This is called Block Disintegration.

→ Exfolation: The breaking of rocks in the form of shells when the upper layer of rocks remain heated and the inner layers cool down.

→ Frost Weathering: In extreme cold regions, the breaking down of rocks due to the freezing and melting of water in the cracks of rocks on regular basis is called Frost Weathering.

→ Pressure Release: When the removal of upper rocks reduces the pressure on lower rocks, then cracks start appearing in rocks. This process is called Pressure Release.

→ Oxidation: The process of combined effect of the mixture of water and oxygen on the minerals of rocks, by which oxides are formed in the minerals and the rocks start decomposing. This is called Oxidation.

→ Carbonation: The atmospheric carbon-dioxide gas (CO2) dissolves in water to form carbonic acid. On coming in contact with it, the lime rocks dissolve rapidly. This is called Carbonation.

→ Desilication: Process of separation of silica from rocks is called Desilication.

→ Igneous Rock: From the three large groups of rocks, the one which is formed when the hot and fluid magma cools down and solidifies, is called Igneous Rock.

→ Hydration: The process of denudation through which the decomposition of rocks takes place on their contact with water and they start breaking down. This process is called Hydration.

→ Dissolution: Rain water dissolves many types of acids and carbonic elements in the rock-materials and creates new chemical mixture. This reaction is called solution.

→ Biological/Organic Weathering: Biological weathering is the weakening and subsequent disintegration of rock by plants, animals and humans.

→ Corraosion: A type of erosive action in which pebbles, stones, boulders, rock particles, etc. along with any factor of erosion erode the land-surface by rubbing or scraping.

→ Attrition: The rock fragments or rock particles being carried by the air, water and glacier smash together and break into smaller particles. This process is called Attrition.

→ Hydraulic Action: The process of the erosion of rocks by the heavy pressure of river water or whirlpool is called Hydraulic Action.

→ Corrosion: The disintegration of rocks by chemical action is called Corrosion.

→ Deflation: The sand, dust or other unorganized rocks-flour being carried away by the winds from one place to another. This process is called Deflation.

→ Cavitation: Waves rising from whirlpool in river form many types of holes at the bottom of the river. This is called Cavitation.

→ Pot Hole: In the plains, a trough is formed at the bottom of the fast-flowing river, which originates as a result of the erosion by pebbles, stones and gravel carried by water-vortex. This is called pothole.

→ Plunge Pool: Deep trough built in a base rock by the erosion caused by pebbles and stones present in the water-vortex which fall down from a height with waterfalls.

→ Plucking: A major process of erosion by glacier through which erosion of the bottom of valley takes place is called Plucking.

→ Suspension: A natural process in which small pieces or particles of un-dissolved substances remain floating in a liquid or gas, but do not settle down due to being light. This process is called Suspension.

→ Deposition: The action of accumulating sediments or materials at a place carried from some other place by a natural process is called Deposition.

→ Sedimentary Rock: Layered rock formed by the deposition of sediments in lower parts of the earth’s surface by the processes of erosion.

→ Gravitational force: Gravitational force is a force that exists among all material objects in the universe. For any two objects or particles having non-zero mass, the force of gravity tends to attract them towards each other.

→ Talus: Creeping down from the slopes, the rock particles accumulate in the foothills. This accumulation or pile of rocks-flour is called Talus.

→ Talus Cone: A cone-shaped accumulation of loose rocks in the foothills, is called Talus Cone.

→ Earth Creep: The action of gradual creeping down of a large landmass from a mountain slope due to gravitational force is called Earth Creep.

→ Rock Creep: The action of gradual creeping down of rock fragments from the height along the slope due to gravitational force is called Rock Creep.

→ Soil Creep: The action of gradual creeping down of soil and rocks-flour from the height along the land-slope due to gravitational force is called Soil Creep.

→ Mudflow: Mudflow is the rapid flow of mud that mixed with sufficient quantity of rainwater or melting snow, so as to liquefy the entire mass and cause the flow.

→ Debris Fall: A type of landslide in which debris collectively falls downwards from the mountain slope or highland due to gravitational force is called Debris Fall.

→ Cycle of Erosion: A major principle of Geomorphology formulated by W.M. Davis.

→ Lateral Erosion: A concurrent process called lateral erosion refers to the widening of a stream channel or valley. When a stream is high above its base level, downcutting will take place faster than lateral erosion; but as the level of the stream approaches its base level, the rate of lateral erosion increases.

→ Pedeplain: Shape-less low flat plain formed in the last stage of aquatic erosion cycle in humid climatic region, on which ruins of hard rocks are found in the form of mounds.

→ Doab, Interfluve or Mesopotamia: The part located in the middle of two rivers interconnecting at a place is called Doab.

→ Aufstegende: According to Penck, the first stage of Erosion Cycle in which landforms develop rapidly.

→ Gleighformige: According to Penck, the mid stage of the development of landforms.

→ Abstegende: According to Penck, the last stage of the development of landforms.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 8 Major Landforms

Relief

• The physical features of the external surface of the earth are called Relief. It includes the high and the low parts of the earth’s surface.
• The formation of different landforms of the earth’s crust is a result of the interactions between the internal and external forces of the earth.
• Adequate variation is found in the shape of various landforms that appear on the earth’s crust – continents, oceans, mountains, plateaus, plains, lakes, etc.
• Landforms are classified into three categories: First Order Relief, Second Order Relief and Third Order Relief.
• The continents and oceans are included in the First Order Relief. The mountains, plateaus and plains are included in the Second Order Relief. The valleys, delta, etc. are included in the Third Order Relief.

Mountain

• Highly elevated part above the earth surface having a narrow peak and steep slope, such a landform is called the Mountain.
• The height of mountains varies according to their formation process, age, location, structure and texture.

Classification of Mountains

• Mountains found in the world are classified on the basis of their origin, height and age.
• On the basis of origin, the mountains are classified into-Folded Mountain, Dome-Shaped Mountain, Accumulated Mountain, Block Mountain and Residual Mountain.
• On the basis of height, the mountains are classified into High Mountains, Average High Mountains, Less High Mountains and Low Mountains.
• On the basis of age, the mountains are classified into-Permian Mountain, Caledonian Mountain, Hercynian Mountain and Alpine Mountain.

Effects of Mountains on Human Life

• Mountains are helpful for human life. They occupy an important place in terms of tourism, recreation, mountaineering, security and from strategic point of view.
• Rivers originate from the mountains by which the facilities of drinking water, irrigation, fisheries and hydro-electricity are available to people.

Plateau

• Elevated part above the earth surface, whose top part is flat and broad, and the edges are with steep slope is called the Plateau.
• The height of plateaus is usually more than 300 meters above the sea-level.

Classification of Plateaus

• Plateaus are classified on the basis of their origin, location, climate and stage of development.
• On the basis of origin, the plateaus are classified into – Lava Made Plateau, Glacial Plateau, Air Made Plateau and Water Made Plateau.
• On the basis of location, the plateaus are classified into – Intermountain Plateau, Piedmont Plateau and Continental Plateau.
• On the basis of climate, the plateaus are classified into-Humid Plateau, Arid Plateau and Snowy Plateau.
• On the basis of stage of development, the plateaus are classified into-New Plateau, Mature Plateau, Old Plateau and Rejuvenated Plateau.

Importance of Plateau

• Fertile soil is formed from plateaus. In addition of being the store-house of many minerals, they are also an ideal place in the formation of water bodies and reservoirs.

Plain

• The surface terrain with low relief and relatively flat, regular and gradual slope is called the Plain.
• Plains are the most favourable for human habitation.

Classification of Plains

• On the basis of the formation-process, plains are classified into two parts – Erosional Plain and Depositional Plain.
• Erosional plains are further classified into-River Eroded Plains, Glaciated Plains, Wind Eroded Plains and Karst Plains.
• Depositional plains are further classified into-River Deposited Plains, Glacio-Fluvial Plains, Loess Plains, Lava-Made Plains and Lake-Made Plains.

Importance of Plains

• Plains are the best place for population inhabitation, development of civilizations, pasture, development of transportation, construction of canals, etc.
• Dense population of the world is found in the plains.

Valleys

• An elongated depression of the earth’s surface usually between the ranges of hills or mountains which is created by tectonic events or external forces.
• Valleys are formed by rivers, by surface deformation, by underground water and by glaciers.

Classification of Valleys

• Valleys are classified on the basis of their formation by tectonic events, formation by external forces, on genetic basis, on basis of their condition, as per the direction of structure and base changes.
• Valleys formed by tectonic events are classified into Synclinal Valley and Rift Valley.
• Valleys formed by external forces are classified into River Valley, Glacial Valley and Blind Valley.
• On genetic basis, the valleys are divided into Consequent Valley, Subsequent Valley, Obsequent Valley, Resequent Valley and Insequent Valley.
• On the basis of condition, the valleys are classified into Youth Valley, Mature Valley and Old Valley.
• As per the direction of structure, the valleys are classified into Ansequent Valley and Superimposed Valley. As per the base changes, the valleys are classified into Drowned Valley and Rejuvenated Valley.

Concept of Landform Development

• Continents and oceans are the largest landforms on the earth’s surface, which are called the First Order Landforms.
• Mountains, plateaus and plains are the Second Order Landforms, while the topographies formed by external forces are the Third Order Landforms.
• The creation of landforms is caused by endogenetic forces, while their destruction is caused by exogenetie forces.
• Concept of geo-plate tectonics helps in gaining information about mountainization, earthquake, volcano and Continental Drift.
• The concepts of geomorphic cycle and erosion cycle solve the problems related to the development of the Third Order Landforms.

Major Landforms Notes Important Terms

→ First Order Relief: Continents and oceans found on the earth are called the First Order Relief.

→ Second Order Relief: Mountains, plateaus and plains found in the continents and oceans are called the Second Order Relief.

→ Third Order Relief: The landforms formed by the process of denudation are called the Third Order Relief.

→ Delta: A delta is an area of low, flat land shaped like a triangle, where a river splits and spreads out into several branches before entering the sea.

→ Endogenetic Force: The force coming from within the earth and causing horizontal and vertical movements are known as endogenetic force.

→ Exogenetic Force: The force forming or occurring on the surface of the earth which are always active in levelling the earth’s surface.

→ Compression: The force falling in opposite direction on any area or substance thereby making the folds in it.

→ Diastrophism: Slow and long-term earth’s movements originated from the internal forces of the earth, which cause deformation on the earth’s crust at a large scale and form huge-sized landforms like oceans, mountains, etc.

→ Epeirogenetic Force: Change in the continental part due to diastrophism.

→ Orogenetic Force: The force responsible for the formation of mountains which is originated due to diastrophism.

→ Anticline: Due to the process of compression, when the rocks take a curved form, then an upward curved fold in the layers of rocks in the earth’s surface is called Anticline.

→ Syncline: Due to the process of compression, when the rocks take a curved form, then a downward and U-shaped fold in the layers of rocks in the earth’s surface is called Syncline.

→ Fossil: The remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form.

→ Dome-Shaped Mountain: When mass-land rises to a higher altitude in the shape of an arc due to strong geological force, then the dome-shaped mountains are formed.

→ Accumulated Mountain: Mountains which are formed by the deposition of volcanic substances and the materials carried by air, rivers, glaciers and sea waves.

→ Block Mountain: The mountain or highland formed due to the downward displacement of landmass between two parallel faults.

→ Relict / Residual Mountain: The mountain or landform which is reduced to more low and flat peak due to denudation process.

→ Denudation: The combined form of the weathering and erosion processes is called Denudation.

→ Tour: The journey conducted with the objective of recreation, income, voyage, business, education, health-benefits, inspection, etc.

→ Irrigation: Artificial arrangement of supplying water to the fields for the growing and production of crops in dry season.

→ Geosyncline: A usually elongated, basin like depression along the edge of a continent, in which a thick sequence of sediments and volcanic deposits accumulates.

→ Intermountain Plateau: Plateau located between the mountains and surrounded by them.

→ Piedmont Plateau: Plateau located on the foot of any mountain is called the Piedmont Plateau. This type of plateau is located at high mountains, plains or in middle of the ocean.

→ Continental Plateau: A vast plateau on the large terrain of a continent on whose borders usually the plain or sea-coast is located, but mountain ranges can also be there at any of its side.

→ Evaporation: A process by which a substance is converted from the liquid to the state of vapour.

→ Escarpment or Scarp: An escarpment is a wide and steep slope on a hill or mountain.

→ Bad-Land: Rough and uneven landform formed on the earth’s surface.

→ Ridge: A long, narrow hilltop, mountain range, or watershed. Ridge located in ocean is called the oceanic-ridge.

→ Monadnock: A residual hill that consists of hard rock rising above a pedeplain in an area formed in the last stage of the cycle of erosion of a landmass.

→ Mechanical Weathering: The action of disintegration in the rocks by physical factors like sunlight, snow, wind, water etc.

→ Corrosion: A type of erosion action in which pebbles, stones, boulders, rock particles, etc. along with any factor of erosion erode the land-surface by rubbing or scraping.

→ Pediplain: Flat surface with extreme gentle slope formed by many sediments found in the last stage of the cycle of erosion in semi-arid region and which has a thin layer of debris on it.

→ Karst Plain: In the region of lime-rocks, when the surface unevenness ends in the last stage of the cycle of erosion of underground water, the Karst Plain is formed.

→ Piedmont Plain: Plain formed by the solidification of sediments coming from the height in the foothills of mountain.

→ Glacio/Fluvial Plain: Plain formed by the deposition made by glaciers.

→ Snow Line: The boundary marking the lowest altitude at which a given area, such as the top of a mountain, is always covered with snow.

→ Loess Plain: Plain formed by the regular deposition of dust by the air.

→ Synclinal Valley: Curved folds occurred in rocks due to the compression force of tectonics action, which causes anticline and syncline. Synclinal valley is formed in subsided part of the folding.

→ Rift Valley: A steep-sided valley formed by the downward displacement of a block of the earth’s surface between two nearly parallel faults.

→ Hanging Valley: A valley that opens at one end to another valley below, having a cliff or steep wall below the point where they meet.

→ Blind Valley: A valley, commonly in karst, that ends abruptly downstream at the point at which its stream disappears Underground.

→ Dip: Dip is the acute angle that a rock surface makes with a horizontal plane.

→ Consequent Valley: The valley formed by the initial streams that originate in a particular region in accordance with the initial slope of the land.

→ Subsequent Valley: The valley formed by streams originated after the consequent stream and joining the master consequent at right angles.

→ Old Valley: This is the last stage of valley. The slope of valley gets extremely gentle in this stage and valley starts becoming flat.

→ Ansequent Valley: In the valley developed before the uplift of a landmass, even after the uplift of the land, the river flows in pre-built valley, then it is called Ansequent Valley.

→ Superimposed Valley: When the valley formed on the upper layers of surface follows the same direction on the lower hard layers of rocks, then it is called Superimposed Valley.

→ Drowned Valley: A submerged coastal valley formed as a result of rise in water level of a ocean or lake or sinking down of proximal place is called Drowned Valley.

→ Rejuvenated Valley: On the fall in sea level, river rejuvenation involves a renewed period of vertical erosion to achieve a new and lower base level, which is called Rejuvenated Valley.

→ Tethys Sea: Large aquatic part extended between the ancient Angaraland and Gondwana land landmasses is called Tethys Sea.

→ Plate: The hard segment of the surface which can float across on heavy semi-molten rock.

→ Continental Drift Theory: The concept according to which the present form of the continents has been attained as a result of the movement of large landmasses.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 7 Earthquakes and Volcanoes

Earthquake

• The crust of the earth is always changing due to endogenetic and exogenetic forces.
• Earthquake is a sudden natural disaster produced by endogenetic forces.
• Shaking of the earth’s surface is known as earthquake. Normally, earthquake refers to sudden shaking taking place on some part of the surface due to geological forces.

Reasons for Origin of Earthquake

• Faulting, volcanic activities, hydraulic weight, contraction of the crust, Isostatic adjustment, Elastic-Rebound Theory, discharge of gases along with plate tectonics, landslides, falling off of ceilings of cliffs and caves are considered responsible for the origin of earthquakes.
• Earthquakes also originate from nuclear explosions carried out by mankind, explosions in mining regions and from deep holes.

Seismology

• The science which studies earthquakes is known as Seismology.
• An instrument known as Seismograph is used to record seismic waves.
• The place from where an earthquake originates is known as seismic focus and the place where the seismic waves are firstly experienced is known as epicentre.

Earthquake Waves

• Shaking takes place in the rocks due to shock experienced at the seismic focus, due to which waves originate.
• Earthquake waves are of three types- P waves, S waves and L waves.
• P waves are the first to reach the earth’s surface. These waves travel through all the three mediums- solid, liquid and gaseous.
• S waves travel only through the solid part. They disappear in liquid part.
• L waves are surface waves. These waves cause maximum destruction.

Types of Earthquakes

• Earthquakes are classified on the basis of their nature and causes.
• Earthquakes are normally classified into artificial earthquakes, natural earthquakes and on the basis of their position.
• Natural earthquakes have been classified into volcanic earthquakes, tectonic earthquakes, isostatic earthquakes and plutonic earthquakes.
• According to their position, earthquakes are classified into land and oceanic earthquakes.

World Distribution of Earthquakes

• Most of the world’s earthquakes are experienced in newly folded mountains, volcanic regions and coastal regions.
• There are three belts of earthquakes in the world-(i) Circum-Pacific Ocean belt, (ii) Mid-Continental belt, (iii) Mid-Atlantic Ridge belt.
• World’s two-third earthquakes occur in the Pacific Ocean belt and 21 per cent earthquakes occur in the Mid-Atlantic Ridge belt.

Effects of Earthquake

• Earthquake is a natural disaster which produces extremely destructive conditions on the earth’s surface in a very short time period.
• Positive and negative impacts of earthquakes are visible on the surface.
• Loss of life and property, breaking of dams, disorganisation of transport routes, collapsing of buildings, evolution of Tsunamis, etc. are the negative effects of earthquakes. Emergence of submerged regions, information about the structure of the earth, sharpening of the depth of ports, increasing in groundwater level, etc. are the positive effects of earthquakes.

Volcanoes

• Volcano is a sudden activity produced by geological forces in which gas, rocks, substances and hot magma erupt from the ridge or crack of the earth’s surface.
• Volcano is a form of vulcanicity.

Causes of Vulcanicity

• Vulcanicity is the result of isostatic disequilibrium, emergence of gases, increase in temperature inside the earth, decline in pressure and plate tectonics.
• A volcano erupts due to structural changes in the interior regions of the earth, condition of vapour, increase in volume, decrease in the pressure of rocks and due to the movement of plates.

Types of Volcanoes

• Volcanoes have been categorized on the basis of duration of emission and nature of emission.
• On the basis of duration of emission, volcanoes have been classified into Active, Dormant and Extinct volcanoes.
• On the basis of nature of eruption, volcanoes have been classified into volcanoes of central eruption and volcanoes of fissure eruption.
• Volcanoes with central eruption have been classified into Hawaiian eruption, Stromboli eruption, Volcanian eruption Pelean eruption volcanoes.
• Pelean eruption volcanoes erupt with the most violent explosion.

Substances emitted from Volcanoes

• Mainly gases and water vapour, solid substances, liquid substances are included in the substances erupted from volcanoes.
• Gases such as carbon dioxide, sulpher dioxide, carbon monoxide, ammonium chloride and solid substances such as rocks of minute to massive size are erupted from volcanoes.
• In the form of liquid substances, magma is produced under the surface and lava is erupted above the surface.

World Distribution of Volcanoes

• Volcanoes are mainly distributed in the Circum-Pacific Ocean belt, Mid-Continental belt, Mid-Atlantic Ridge belt and East African belt.
• The Circum-Pacific Ocean belt is also known as the Ring of Fire.
• The Circum-Pacific Ocean belt starts from Mount Erebus of Antarctica and passes by Andes, Rockies Mountains, turns from Alaska and joins the Continental belt while passing by the south-eastern coastal regions.
• Mount Barren, Popa, Elbrus, Etna, Visuvius are the volcanoes of Mid-Continental belt.
• The Mid-Atlantic belt is spread in ‘S’ shape in the Atlantic Ocean.
• East African belt proceeds in the south of Israel from the Red Sea and from the East African rift valley and joins up till Madagascar.
• Minor distribution of volcanoes is found in Hawaiian Islands, Mauritius and Kamero in the Indian Ocean.

Effect of Vulcanicity

• There are creative and destructive effects of vulcanicity.
• Formation of fertile soil, development of mineral belts, etc. are creative effects of vulcanicity.
• Loss of life and property, pollution of the environment, loss to cultural landscape, destruction caused due to submergence of regions in coastal areas, etc. are destructive (harmful) effects of vulcanicity.

Earthquakes and Volcanoes Notes Important Terms

→ Earthquake: A sudden trembling or movement on the earth’s surface, which originates in natural form under the earth’s surface.

→ Volcano: An opening in the earth’s crust from which hot liquid lava, gases, pieces of rocks, ash, water, etc. are erupted.

→ Endogenetic Force: Force which is originated under the earth due to which horizontal and vertical movements take place.

→ Exogenetic Force: Force which is produced or which is active on the earth’s surface which always remains active in levelling the earth’s surface.

→ Isostasy: The state of gravitational equilibrium between the Earth’s crust and mantle which is found between the elevated parts (mountains, plateaus, plains) and depressed parts (seas, oceans) of the earth.

→ Fault: A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock-mass movement in which rocks get transferred from one place to another place, besides creating an edge on the earth’s surface.

→ Tension: Force which is exerted on the rocks due to pull from the opposite side of the rocks.

→ Compression: Force which is produced due to the pressure exerted from both sides in the form of horizontal force in a region.

→ Cracking: Breaking up of rocks due to action of intolerable force due to the process of exertive forces.

→ Rift Valley: A lowland between two parallel highlands whose breadth is extremely less but the length is more.

→ Vulcanism or Vulcanicity: Volcanic activity under which all the processes from the origin of hot liquid Magma inside the earth’s surface up to its emergence on the surface and the process of cooling down and solidification of the substances is included.

→ Dam or Embankment: A wide and high wall built of rocks or concrete on the estuary or bank of the water-flowing route of a river to stop its water flow, change its direction or to control the flow of water.

→ Radiation: That process by which a substance or object emits radioactive energy in the form of heat. The heat of that substance declines due to this and it gets cooled down.

→ Ocean Deeps: The deepest part of oceanic bottom which is found in a limited region of oceanic bottom and whose incline is extremely sharp.

→ Erosion: Weathering of earth’s surface or rocks by various natural forces. Flowing surface water, underground water, oceanic water, wind, glaciers and ice are the major factors of erosion.

→ Deposit: Deposition is the geological process in which sediments, soil and rocks are added to a landform or landmass.

→ Plate: Fixed landforms are called plates.

→ Divergent Boundaries: When two plates move towards the opposite direction from each other then a new crust is formed which are called divergent boundaries.

→ Convergent Boundaries: When one plate is suppressed under another plate and where the earth’s crust is destroyed, it is known as convergent boundary.

→ Subsidence: Subsidence is the motion of a surface (usually, the earth’s surface) as it shifts downward relative to a datum such as sea level. The process of gradual descent of a large volume of wind or its settling down.

→ Cliff: A cliff is a vertical, or nearly vertical, rock protuberance which is found on a seashore or on hills.

→ Seismology: The science which studies seismic waves on the basis of graph drawn by instrument which records earthquakes.

→ Seismograph: The instrument which is used to record seismic waves.

→ Seismic Focus: The centre which is situated under the earth’s surface from where the earthquake originates.

→ Epicentre: A point situated on the earth’s surface which is right above the centre of the origin of earthquake or seismic focus.

→ Seismic Waves: Waves of energy that are generated by an earthquake or other earth vibration and that travel within the earth or along its surface. This wave firstly reaches the epicentre from where it is transmitted in various directions.

→ Longitudinal Wave: Those seismic waves which vibrate in the same direction as the wave travels, just like sound waves, and the vibration of their molecules takes place to or fro in the direction of their travel.

→ Surface Wave: That seismic waves which travels along the surface of the earth.

→ Artificial Earthquakes: Earthquakes which originate due to man-made activities.

→ Isostatic Earthquakes: Such earthquakes which originate due to distortion in the balancing process of the earth’s surface.

→ Plutonic Earthquakes: Earthquakes which originate in extreme depth inside the earth are known as plutonic earthquakes.

→ Continent: An extended land part is known as continent. Generally, it is marked by naturally separating physical boundaries.

→ Transform Faults: A special type of fault which determines the boundary between two moving plates.

→ Dormant Volcano: Such volcanoes which remain inactive for some time and then erupt again are known as dormant volcanoes.

→ Extinct Volcano: Those volcanoes which have not erupted for a significant time period are known as extinct volcanoes.

→ Peninsula: That part of a continent or mainland which extends towards the reservoir or sea and is surrounded by water from three or most of the sides.

→ Cultural Landscape: Landform or landscape which originates due to the change in natural conditions effected by mankind.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 6 Rocks

→ The upper layer of the earth (earth’s crust) is formed from the composition of various
minerals.

→ The word ‘rock’ is used for any hard object.

→ According to geological perspective, all the substances that have formed the earth’s crust, whether they are hard or soft, are called rocks.

Types of Rocks

• There are 3 types of rocks – Igneous Rocks, Sedimentary Rocks and Metamorphic Rocks.
• The nature of the crust is hard or soft according to the nature of the rocks which form it.

Igneous Rocks

• Rocks made of hot and fluid magma and lava are called igneous rocks.
• Being the first to be formed, these are called the primary rocks.
• About 95 percent part of the igneous rocks extends to the thickness of up to 16 km. in the upper part of the crust.
• The features like lack of layers, lack of fossils, lack of porosity, crystallized form, hardness, and abundance of metallic minerals are found in these rocks.

Classification of Igneous Rocks

• On the basis of the place of formation, the igneous rocks are classified into two parts – Intrusive and Extrusive Rocks.
• Intrusive igneous rocks are further classified into Plutonic and Hypabyssal Rocks.
• Granite is Plutonic; Phacolith, Lacolith, Lapolith and Dykes are Hypabyssal; Gabbro and Basalt are Extrusive Igneous Rocks.
• On the basis of chemical composition, the igneous rocks are classified into Acidic, Basic, Intermediate and Ultra-Basic Rocks.

Sedimentary Rocks

• These rocks are formed by the solidification of the layers of sediments through the processes of weathering and erosion.
• These rocks are found on almost 75% part of the total earth’s surface.
• Sedimentary rocks contain several layers, strata, are porous contain fossils and are soft.

Classification of Sedimentary Rocks

• Sedimentary rocks are classified on the basis of the resources and the sediments used in their formation.
• On the basis of the sediments used, these rocks are classified into clastic rocks, compared of fragments or clasts, of pre-existing minerals and rocks. A clast is a fragment of gealogical detritus, chunks; Organically Formed Rocks and Chemically Formed Rocks.
• On the basis of the resources used in the formation, these rocks are classified into Aqueous Rocks, Aeolian Rocks and Glacial Rocks.

Metamorphic Rocks

• Rocks made by basic changes in the properties and structure of the original rocks without their disintegration and dissociation are called metamorphic rocks.
• For the metamorphism of metamorphic rocks, water, heat and pressure play an important role.
• These rocks are harder than the original rocks and have an abundance of metallic minerals.

Metamorphism of Rocks

• Metamorphism of rocks is divided into Thermal Metamorphism, Regional or dynamic Metamorphism, Hydro Metamorphism and Thermo-Hydro Metamorphism.
• In the metamorphism of the igneous rocks, granite metamorphosed into gneiss, basalt into amphibolite and gabbro into serpentine.
• In the metamorphism of the sedimentary rocks, sandstone metamorphosed into quartzite, limestone into marble, shale into slate and coal metamorphosed into graphite and diamond.
• Re-metamorphism of some metamorphic rocks, like slate metamorphosed into schist and schist re-metamorphosed into phyllite.

Rocks Notes Important Terms

→ Igneous Rocks: The word igneous is originated from the Latin word ignis, the meaning of which is fire.

→ Sedimentary Rocks: The disintegration, dissociation and transport of rock-powders of the existing rocks takes place through the various means of weathering and erosion. The rocks formed as a result of accumulation of the sediments at a place are called sedimentary rocks. Due to their layered structure, they are also known as the Layered Rocks.

→ Metamorphic Rocks: The meaning of metamorphic is – change in the form. Due to the changes in the forms of the igneous and sedimentary rocks by the action of heat and pressure, the metamorphic rocks are formed.

→ Fossil: The remains or impression of a prehistoric plant Ot animal embedded in rock and preserved in petrified form.

→ Weathering: The process by which rocks are broken down into small grains and soil.

→ Chemical Weathering: A process of weathering under which dissociation begins as a result of chemical changes in the rocks by which erosion of the rocks takes place.

→ Physical Weathering: The process of disintegration in the rocks by physical factors like sun’s heat, light, wind, water, etc.

→ Metallic Minerals: The minerals from which metals are obtained are called metallic minerals, like – iron ore, copper ore, manganese ore, etc.

→ Plutonic Rocks: The rocks formed when the lava is cooled down and solidified beneath the earth’s surface are called plutonic rocks.

→ Phacolith: The lava solidified in the syncline of folded mountains at the time of volcanic eruption.

→ Lacolith: A large mass of igneous rocks formed beneath the earth’s surface, whose lower part is generally flat and upper part is in the shape of a dome.

→ Lapolith: Lapolith is a word of the German language, whose meaning is a shallow basin.

→ Dykes: When the lava deposits in the cracks are almost at the right angle of the earth’s surface, then a wall-like structure formed is formed.

→ Sills: When the lava flows, sills is a group of igneous rocks formed in the shape of layer.

→ Batholith: When a large body of magma gets cooled down at more depth in the earth’s crust, then it develops into the shape of a dome.

→ Acidic Rock: Rocks formed of high content silica lava. The amount of silica is more than 65% in these rocks.

→ Basic Rock: The amount of silica is in between 45% to 55% in these rocks.

→ Ultra-Basic Rock: Rocks in which the amount of silica is less than 45% are called Ultra-Basic Rocks.

→ Denudation: The combined processes of weathering, erosion, transportation and deposition of the rocks is called denudation.

→ Vegetation: All plant life of a region. This includes all plant species like algae, grass, shrubs, trees, etc.

→ Rocks-Flour Formed Rocks: Rocks formed of the fine solid matter originated by the abrasion of any glacier bottom.

→ Loess: The deposits of the very fine particles of soil and dust particles blown away by the winds.

→ Organic Rock: Rocks in which the debris of living-organisms and vegetation is found in abundance.

→ Aqueous Rock: Rocks which are formed by the deposition of sediments in aquatic parts are called Aqueous Rocks.

→ Aeolian Rock: The accumulation of materials caused by air or related to it, is called Aeolian rock.

→ Glacial Rocks: Rocks which are formed by the transportation and deposition of pebbles and boulders by the glaciers.

→ Metamorphic Rock: Rocks which are formed by the changes in the forms of igneous and sedimentary rocks due to the action of heat and pressure.

→ Thermal Metamorphism: The process of change in the form of the igneous and sedimentary rocks and rebuilding of granules in their structure by the effect of extreme heat.

→ Hydro Metamorphism: The process of change in the rock-minerals in the form of a solution by the mixing of chemical materials with water.

→ Thermo-Hydro Metamorphism: Metamorphism of rocks occurred due to the spread of hot water over the top of the rocks.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 5 Origin of Continents and Oceans

→ Continents and oceans are the first class relief present on the earth’s surface. The Continental Drift and Plate Tectonic theories have been accepted for their origin.

→ The continents represent the terrestrial part while the oceans represent the aquatic part.

Continental Drift Theory

• The German scholar Alfred Wegener, introduced the Continental Drift Theory in 1912.
• Wegener considered two alternatives to be the main ones for the purpose of rendering his theory. First, if the climatic condition is variable, then the terrestrial part is stable. Second, if the terrestrial part is variable then the climatic condition is stable. Based on the second option, he had set the theory of the displacement of the continents.
• According to Wegener’s Continental Drift Theory, there existed one big landmass which he called Pangaea which was surrounded by one big ocean called Panthalassa.
• He considered Pangaea to be a Sial floating on a high density layer.
• According to Wegner, the land flows towards the equator and towards the west.
• For this flow of continents: (i) Gravity / Flotation force (ii) Tidal force were considered responsible.
• The gravity or flotation force causes the flow of land towards the equator, while the tidal force causes the flow of land towards the west.
• With the separation of North and South America the Atlantic ocean was formed. Being separated from, Australia and Antarctica, the Indian ocean was formed. The remaining part of the Panthalassa was called the Pacific Ocean.

Evidences in Support of the Continental Drift

• Proof of geographical, geological, Geodesical and biological evidences and Paleoclimateogical are found in favour of the continent drift theory.
• In the geographical proofs, the formation of equilibrium in the Atlantic shores, the alignment of mountains and the new folded mountains are the main source.
• The geological evidence included the similarity in structural and stratigraphical similarities. The geodesical evidence included the geo-morphology of Greenland and Canada. The biological evidence included the fossils evidence and bio-diversity.
• The process of mutual matching of the continents is called jig-saw-fit.

Criticism of Continental Drift Theory

• The continental drift theory has been criticized on the basis of geographical, geological, geometric, biological and paleoclimatological discrepancies.
• Non-matching of the Brazilian coast and the, Gulf of Guinea, only the partial similarities in structural and topographical configuration on the Atlantic shores, the effects of gravitational force and the diversity of the organisms have been criticized.

Plate Tectonics

• The word plate was first used by Tuzo Wilson. In this theory, 6 large and 20 minor plates are considered to make up the earth’s crust.
• The main plates include Indian, Eurasian, African, American, Pacific and Antarctic plates.
• There are three types of plates: (i) Continental plate, (ii) Oceanic plate and (iii) Continental-oceanic plate

Plate Margins

• The plates have three margins: the constructive plate margins, the destructive plate margins and the protective plate margins.
• The space formed by the divergence of the two plates form a new one. It is called the constructive plate margins.
• The convergence of the plates leads to the disperal/erosion of plates. This is called the destructive plate margins.
• When the plates create neither the erosion nor the formation of new substances, this is called the protective plate margins.
• The motion of the plates is due to radioactivity, convection currents and geothermal energy.

Evidenced of Plate Tectonics

• Sea floor spreading, continental drift, widening of the river valleys, etc. are considered to be the evidences of plate tectonics.
• Expansion of the ocean bottom proves the concept of plate tectonics.
• Paleomagnetism and sea-bottom transmission have proven mobility in the land.
• The width of valleys, seismic events, volcanic activity and mountain formation process also certify plate tectonics.

Origin of Continents and Oceans Notes Important Terms

→ Continent: The extensive stretch of land extent formed by the rocks is called the continent.

→ Plate: Fixed crustal components are called plates.

→ Zone: A zone is an area that has particular features or characteristics.

→ Carboniferous Period: A part of the paleozoic era which was characterized by the process of coal formation. This period was 35 million years ago.

→ Pangaea: In early geologic time, a supercontinent that incorporated almost all the landmasses on the Earth.

→ Panthalassa: Panthalassa means, ‘water only water’. The name given by Wegener to the aquatic counterpart of Pangaea.

→ Geosyncline: A very large trough like depression in the earth’s surface containing masses of sedimentary and volcanic rocks.

→ Angaraland: The northern part of the Pangaea continent described by Wegener, which included Europe, Asia, and North America. It was also called Laurasia.

→ Gondwanaland: The southern part separated from Pangea, which is currently an isolated plot consisting of Africa, Madagascar, Australia, South America, Antarctica and the indigenous parts of Peninsular India, etc.

→ Laurasia: An ancient continental terrain, which was believed to be separated and later from this, Europe, North Asia, North America and Greenland were created. This northern part of Pangea is called Laurasia.

→ Eurasia: Europe and Asia were jointly called Eurasia which was a part of Angaraland.

→ Gravitation force: The attraction force of the earth due to which, all things are attracted to it.

→ Tidal force: The force associated with the attraction of the sun and the moon.

→ Equator: Latitudinal line of zero degree, dividing the earths into the Northern and the Southern Hemispheres.

→ Jig-saw-fit: Status of re-integrative profile of space segments divided by continent in continental drift theory by Wagener.

→ Gulf or Bay: A deep inlet of the sea almost surrounded by land with a narrow mouth or a very large area of sea surrounded on three sides by a coast.

→ Fold Mountain: Fold Mountains are formed as a result of the compression of tectonic plates, which leads to the formation of large fold like structures on the earth’s crust.

→ Sediments: Substances like gravel, sand, punk and lime deposited on the sea bottom, which are transported and deposited by wind, water, glacier or gravity.

→ Glaciation: A microclimatic process or activity under which the icebergs expand on the wide area of the land after the decreases in temperature due to climate change.

→ Fold: Curved twist or tilt in surface rocks caused by their movement due to geothermal force.

→ Reconstruction: The process of re-creation of continents on the crust.

→ Crust: The topmost layer of the Earth on which continents and oceans are formed.

→ Mantle: Around 2900 km thick layer, situated between Crust and Core, whose density is found from 3.1 to 4.75.

→ Lithosphere: Lithosphere is the outermost layer of the earth consisting of the crust and the upper mantle portion of the earth. Lithosphere is responsible for the hard and rigid surface of the earth on which humans exist.

→ Divergence: The process of moving (sliding) in the opposite directions of any two objects is called Divergence.

→ Deeps: The deepest part of the ocean bottom is found in certain areas of the sea bottom, along with the sharply-sloping shield.

→ Ridge: Long and narrow hill with steep slope. Ridge located in the ocean is called inter marine ridge.

→ Continental Plate: Plate associated with continent. The whole or most part of this plate is the land.

→ Ocean Plate: Ocean-related plate. The whole or most part of this plate comes under the ocean bottom.

→ Convergence: When two plates move towards each other from different directions, one of the plates climbs over the other. Such process is called convergence.

→ Transform faults: A special type of fault which determines the separating boundary of two moving plates.

→ Asthenosphere: Below the crust, there is a weak strip in which the rocks are in liquid plastic form. Its surface extends to the depth of 70 – 200 km.

→ Rift Valley: The deep part of the two parallel faults whose width is less but the length is greater.

→ Island festoon Arc: A long, curved chain of oceanic islands. There is often a long and narrow gap in the ocean from the insular arc to the ocean.

→ Geologist: A person who studies the interior of the earth.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 4 Interior of the Earth

→ The interior of the Earth is invisible and unreachable. Due to the rapid increase in temperature with depth, more deep mining and exploration work are not possible.

→ Lava and hot gases coming from volcanic eruptions are the source of information about the internal structure of the earth.

→ Seismology provides more scientific and authentic information about the geological structure of the earth’s interior.

Sources of Information about the Interior Structure of the Earth

• Information about the interior structure of the earth is obtained from artificial sources, meteorites and natural resources.

Artificial Sources

• Temperature, pressure and density are artificial sources of information about the internal structure of the Earth.
• Going from the surface of the Earth to the center, the temperature increases by 1°C every 32 metres.
• Rocks are plasticum solid because of the high pressure and high temperature in the center.

Meteorite Shower

• Meteors are a part of the solar family. They sometimes fall on the ground.
• Nickel and iron are found in the composition of meteors. Earth also reflects the properties of magnetism. Therefore, it should have the same composition.

Natural Sources

• Volcanic eruption and earthquake science are the natural means of obtaining information about the interior structure of the earth.
• Magma, lava and seismic waves coming out of the volcano provide information about the earth.
• An earthquake is the accidental vibration of the crust. The point at which the vibrations starts it called the earthquake origin.
• Seismic energy travel in the form of P, S and L waves. The area between the 105° – 145° to the seismic center is the seismic shadow area.

Layers of Interior Earth

• Three layers of earth are crust, mantle and core.
• Crust is the outer layer, mantle is the middle layer and core is the innermost layer of the Earth.
• The average thickness of the crust is 30 km, the mantle layer extends from crust to 2900 km whereas the core extends from 2,900 km to 6371 km.
• The core is divided into two parts – the outer core (2900 – 5150 km) and the internal core (5150 – 6371 km).

Classification of Suess

• Based on the chemical classification by Suess, the earth is divided into three layers – Sial, Sima and Nife.
• Sial is made from silica and aluminum, Sima is made from silica and magnesium and Nife is primarily from nickel and ferrium.
• The average density of Sial is 2.9 – 4.7 and the density of Nife is 11.

Classification by Van der Gracht

• Van der Gracht has divided the earth into four layers – the outer silica crust, internal silicate layer, mixed metals and silicate layer and metallic center.
• The external silica crust is made of silica, aluminum, potassium and sodium, whose density is 2.75 – 3.1. Its depth varies under the continents and the oceans.
• Internal silicate layer is 60 – 1200 km, whose density is 3.1 – 4.75. It is made of silica, magnesium and calcium.
• The internal silicate layer is up to 1200 – 2900 km. Its density is up to 4.75 – 7.8. Metallurgical center extends from 2900 km. to the centre of earth. Its density is greater than 11.

Interior of the Earth Notes Important Terms

→ Earth: A member planet of the Solar System, which is inhabited by humans and which revolves around the sun in a fixed orbit, while rotating on its axis.

→ Volcano: A mountain or hill, typically conical, having a crater or vent through which hot and fluid lava, rock fragments hot vapour, ashes, water, etc. erupt from the earth’s crust.

→ Rock: In simple language, a solid body is called a rock.

→ Meteorite Shower: The small celestial bodies (meteors) present in the solar family, residual part of which fall on the earth. They start to burn when they Earth’s atmosphere.

→ Magma: The molten rock found below the surface of the Earth with which hot gases thick, often found.

→ Seismology: The science in which the earthquake waves are studied based on the vibration recorded by special instruments.

→ Seismic Focus: The point in the crust below the surface of the earth from where the earthquake originates.

→ Epicentre: The point on the earth’s surface which is located right above the seismic focus.

→ Surface Waves: The seismic waves which travel on the earth’s surface. These waves travel along the circumference of the earth.

→ Earthquake Shadow Zone: These are those areas on the ground where no seismic wave is recorded.

→ Crust: The crust forms the topmost part of the Earth. It is mainly the outer layer of the Earth which forms continents and oceans.

→ Mantle: Around 2900 km thick layer, situated between Crust and Core, whose density is found from 3.0 to 3.4.

→ External Core: This is the upper part of the Earth’s core found in the liquid state. It is believed to spread from 2900 km to 5150 km.

→ Internal Core: The Earth’s layer is the lower part of the core which is in solid state. It stretches from 5150 to the center of the earth.

→ Astheno Sphere: Below the crust, there is a weak strip in which the rocks are in liquid plastic form.

→ Sial: Term used for relatively light rocks of the lithosphere.

→ Sima: Term used for relatively heavy rocks of the lithosphere.

→ Nife: The word is used for the central part of the earth made of heavy substances, nickel (ni) and iron (fe).

→ Ocean: Very large open aquatic part of the Earth that is filled with saline water.

→ Zone of Mixed Metals: According to Van der Gracht, the third layer 1200 – 2900 km in the internal structure of the earth.

→ Metallic zone: The earth’s innermost part extending from 2900 km to 6371 km. It is made of nickel and iron.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 3 The Earth: Form, Motions, Location and Calculations of Time

→ In ancient times, the entire universe was considered to be ‘earth-centric’ and the earth was described as stationary, flattened or disc-like.

→ In Indian text ‘Aryabhatiya’ the earth was described as spherical. Aryabhatta described the earth round like a ball, and rotating on its axis from west to east direction, which creates day and night.

→ Copernicus and Galileo described the Sun as being the centre of the solar system and described the shaped of the Earth and all other celestial objects to be spherical.

→ Man-made satellites and Apollo spacecraft have proved that the Earth is spherical. However, but due to its flatness on the poles, it is considered as flattened or short axis spheroid in form.

→ The calculation of the perimeter of Earth was done in 256 BC by the Greek scholar Eratosthenes, which was almost equal to scientific calculation.

→ The Indian scholars who calculated the age, circumference, diameter and radius of the Earth were similar to scientific calculations.

Important Facts Related to the Earth

• The equatorial diameter of the earth is 12756 km, polar diameter is 12713 km, whereas the equatorial perimeter is 40077 km and the polar perimeter is 40000 km.
• The total area of the Earth is 510 million square kilometers, out of which the terrestrial area is 149 million square kilometers while the oceanic area is 361 million square kilometers.
• The Earth’s average density is 5.517 grams per cubic cm, its weight is 6,600 trillion tonne and the mass is 5.882 × 1021 tons.

The Motions of the Earth

• Earth has two movements – daily or rotation speed and annual or revolution speed.
• Daily or rotational day and night. The earth revolves around its axis in 24 hours.
• Due to the rotational motion of the Earth causes, there is more protrusion on the equator and flattening on the poles.
• The earth is tilted at an angle of 23$$\frac{1^{\circ}}{2}$$ on its axis, which is why the joy of different seasons is experienced in both the hemisphere.
• Earth revolves around the Sun in 365$$\frac{1}{4}$$ days. Its revolution speed is 29.6 km per second.
• The average distance of the sun from the Earth is 150 million km. When the earth is at the greatest distance (152 million km) from the Sun called as Aphelion and at the lowest distance (147 million km) it is called perihelion.
• Seasons are formed by the revolution of the Earth.

Solstices and Equinoxes

• The line that separates the illuminated and dark parts of the earth is called the circle of illumination.
• Due to the location of the Sun on June 21 on the tropic of Cancer summer solstice occurs, and on December 22, the position of the Sun is on the tropic or Capricorn, due to which the winter solstice occurs.
• Solstices give mobility to the Earth and there is a change in the position of the sun, stars and constellations.
• In India, Makar Sankranti has special significance. Sun is worshipped on this day.
• On earth, 21 March and 23 September have equal duration of day and night. when in the northern hemisphere, the spring season begins on March 21. Hence it 18 called spring equinox. on 23 September, there is an Autumn Equinox in the southern hemisphere.
• On Poles 6-month day and 6-month night occurs.

Latitudes and Longitudes

• The imaginary lines drawn from east to west on the globe are called, latitude and longitude is drawn from north to south.
• Latitudinal and longitudinal lines intersect each other at right angles. the grid made from these lines is called ‘land grid’.
• The equator divides the earth into two parts. It is called 0° latitude line.
• 90.90 latitudes are present from the equator to the north and south.
• The distance between two consecutive latitudes is 111 km.
• The 23$$\frac{1^{\circ}}{2}$$ latitude line in the northern hemisphere is called the Cancer Line, the 66$$\frac{1^{\circ}}{2}$$ North latitude is called the Arctic circle, while 90° North latitude is the North pole.
• The 23$$\frac{1^{\circ}}{2}$$ latitude line found in the southern hemisphere is called Capricorn Line, 66$$\frac{1^{\circ}}{2}$$ is called the Antarctic Circle and 90° is called the South Pole.
• The area between 0°-30° latitude on both the hemispheres is called the area of the lower latitudes, the area between 30°-60° latitude is called mid-latitudes and 60°-90° is called high latitudes.
• The area between 0°-23.5° latitudes in both the hemispheres is called tropical zone the region between 23.5°-66.5° latitudes is called temperate zone and the area between the 66-90° latitude is called the Frigid zone.
• The line drawn in the north-south direction passing through Greenwich, located near London, is called the prime meridian or the Greenwich meridian. It has 180°-180° longitudes to ita east and west.
• In the opposite face of the earth to the meridian prime meridian (0°), there is a 180° international dateline.
• This distance increases between longitudes approach the equator and decrease towards the poles. It becomes zero on the poles.
• On difference of each. an increase of 4 minutes occurs, and afterl5 longitudes time increases by 1 hour.

Time

• Earth rotates 360° in 24 hours. That is why it takes 4 minutes to rotate every 1° longitude.
• Time to other places can be easily determined according to the Greenwich Time.

Local Time

• The time of each place calculated according to the longitude, is called its local time.
• The local time is related to the height of the mid-day sun.

Standard Time

• For a standard time, in each country, one specific longitude is assumed to be the standard longitude.
• From 0° longitude, the standard timeline of other countries is determined. The standard time line of India is 82.5 East longitude whose time is 5.30 hours ahead of the Greenwich meridian.

Time zones

• Countries with more expansion have more than one standard time-line.
• The whole earth is divided into 24 time zones.
• There are 5 time zones in Canada, 4 in the United States, 3 in the continent of Europe, and 11 time zones in Russia.

International Time

• The international time is determined by the Greenwich meridian. The time of the Greenwich meridian is called the International Time.
• The computation of all the time zones is done only according to the meridian line.

International Date Line

• The 180° longitude is considered the international dateline. One day from one day it will increase from east to west, whereas one day will be decreased upon crossing it from west to east.
• This line is not straight and it has been made according to need zig-zag.

Equation of Time

• The time withing which a place is rotated on the axis and then comes to the same place that the sun starts to glow over it, is called solar Day.
• The apparent time duration is determined on the basis of the sun’s glowing conditions.
• When the time is not determined according to the position of the sun, but on average time, it is called mean time. Watches run according to the mean time. This the same time is the time of the clock.
• If the sun is perpendicular overhead some time after 12 o’clock by the clock, then the time equation will be positive (+) and if the sun is shining before the 12 o’clock, then the time will be negative (-).
• Only four days in the year 16 April and 15 June, 1 September and 25 December the mean time, and apparent time are equal.

The Earth: Form, Motions, Location and Calculations of Time Notes Important Terms

→ Environment: The sum of physical, biological, and chemical conditions, which experienced a creature or creatures. Generally, the cover found around us is called environment.

→ Universe: The Universe is the eternal sky in which innumerable stars, planets, suns, earth, moons, meteors, asteroids etc. are found. It is also called the cosmos.

→ Solar Eclipse: Due to the position of the moon between the sun and the earth, some part of the sun or the entire part of the sun is not visible from the earth or it seems dark, due to obstruction of the moon. This is called a solar eclipse.

→ Lunar Eclipse: When the earth is positioned between the Sun and Moon, the shadow of the earth falls on the moon, due to which the shadow part of the moon is dark and Lunar eclipse occurs.

→ Planet: Such a celestial body in the universe that revolves around a star. The planets found in our solar system rotate around the sun.

→ Satellite: A body or machine which is sent into orbit of a planet by man, revolves around the related large body.

→ Pole: 90° latitude in the north and south of the equator, where the distance between all the longitudes becomes zero are called Poles.

→ Equator: The imaginary circle passing midway between the two poles on the globe which divides the globe into two equal parts is also called 0° latitude or the equator completes one rotation.

→ Rotation: The process of rotating the Earth on its axis. Earth rotates on its axis in 24 hours.

→ Stars: Radiant cosmic bodies made of gaseous matter are called stars. They contain hydrogen 70%, helium 28%, 1.5% carbon, nitrogen and neon and 0.5% Ferrous elements.

→ Latitude: The angular distance of a point located on the land surfaces in the north or south of the equator, measured from the centre of the earth.

→ Revolution: Movement of the earth around the Sun in a fixed, elliptical orbit is called Revolution. Earth completes one revolution of the sun in 365$$\frac{1}{4}$$ days.

→ Aphelion: The position of the Earth when it is at the greatest distance from the Sun in its orbit.

→ Perihelion: When, in the earth’s solar orbit the distance between the Earth and the Sun is minimal, then this situation is called Perihelion.

→ Solar Energy: The heat or energy received from the sun is called solar energy.

→ Tropic of Cancer: 23$$\frac{1^{\circ}}{2}$$ North latitude is the last boundary of the perpendicular position of the Sun in the Northern Hemisphere, Further north of which, the sun rays never fall perpendicularly on the surface of the Earth.

→ Tropic of Capricorn: 23$$\frac{1^{\circ}}{2}$$ South Latitude. This is the southernmost boundary, upto which, the sun is perpendicular on the earth.

→ Spring or Vernal Equinox: On March 21, when the sun is perpendicularly overhead on the equator. This event is called Spring Equinox.

→ Arctic Circle: The 66$$\frac{1^{\circ}}{2}$$ latitude circle on the north side of the equator is called Arctic Circle.

→ Antarctic Circle: 66$$\frac{1^{\circ}}{2}$$ South latitude. Due to the inclination of the axis of the Earth, on the summer solstice of the southern hemisphere Antarctic circle.

→ Longitude: The imaginary line that joins the north pole with the South Pole is called longitude.

→ Globe: Term used for any spherical body (spheroid) or earth.

→ Prime meridian line: The zero degree longitude line that passes through the Royal Observatory located at Greenwich, Great Britain.

→ Graticule: The and grid made by intersecting latitude and longitude lines on the globe is known as Graticule.

→ Lower Latitude zone: The area on both sides of the equator between 30° North to 30° South latitudes is called the Lower Latitude zone.

→ Median Latitude zone: The area between 30° and 60° north and south latitudes on either side of equator the globe is called the middle latitude zone.

→ High Latitude Zone: The area found between 60°-90° North and South latitudes on both sides of equator on the globe is called high latitude zone.

→ International Date Line: An imaginary line with approximately 180° longitude on the globe, which passes through the aquatic part of the Pacific Ocean.

→ Local time: Local solar time of a place, which is determined by the position of the sun.

→ Standard Time: Normally, the mean time of the meridian line passing through a country or its any area, which is used for all the country or entire region.

→ Time Zones: The standard time on the Earth is determined not by any single meridian but by different lines. Earth is divided into 24 time zones.

→ Island: Land segment surrounded by water which may be situated in an ocean, lake or river.

→ Continent: Large extents of land raised above sea level which are surrounded by oceans from all sides or from most sides.

→ Strait: Narrow water or sea expanse connecting two large oceans.

→ Solar Day: The time within which a place is rotated on the axis and comes to the same position that the sun begins to shine on it, is called Solar Day.

→ Apparent Time: The time of an area determined by the position of the sun overhead by viewing.

→ Mean-time: Because the position of the Sun is different in different regions, the process of adjusting time back or ahead of an area is called the mean time.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

→ Earth is a living planet that is at the third place from the Sun in the sequence of planets. It is the planet where life the only planet in our solar system.

→ Life on earth has been possible due to the sun, due to its certain distance from the sun and optimum solar insolation, ideal for sustenance of life.

→ Some planets like the Earth have been discovered, which may have the possibility of having.

Origin of the Earth

• Many philosophers and scientists have presented their concepts in relation to the origin of the Earth.
• Immanuel Kant had interpreted the Gaseous hypothesis, which was introduced in 1796 by Laplace as the Nebular hypothesis.
• In 1900, Chamberlain and Moulton gave the Planetesimal hypothesis and James Jeans a Tidal hypothesis.
• Otto Schmidt rendered Inter-stellar Dust hypothesis in 1950.

Origin of the Universe

• The modern theory of the origin of the universe in modern times is the ‘Big Bang Theory’. It is also called the ‘Expanding Universe hypothesis’.
• According to this theory, the distance between the galaxies is increasingly expanding the universe.
• The incident of Big Bang took place 14 billion years ago, in which several tiny balls explosions occured.
• A scholar named Hoyle rendered a steady-state concept.

Formation of Stars

• There is a large number of countless stars in a galaxy. These galaxies are formed by the solidification of various substances.
• The construction of the galaxy begins along with the storage of hydrogen clouds around solidifying heavier matter. These gaseous celestial bodies are called nebula.
• Huge volumes of gas evolved in the nebula. These gaseous clouds became increasingly dense and this started the formation of the stars.
• The stars were formed around 5 to 6 billion years ago.

Light Year

• Light year is a measure of distance. The speed of light is 3 lakh km. per second.
• The distance which fight covers in its travel in one year is called a light year.
• The average distance between the Earth and the Sun is 14.96 crore kilometers.

Formation of Planets

• The stars are lacalised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud.
• Planetesimals have been formed due to the condensation of the gas clouds.
• Large number of small planetesimals accrete to form a fewer large bodies in the form of planets.

Solar System

• Nebula is considered to be the Father of the Solar System. There are eight planets in our solar system.
• Our solar system consists of the Sun, eight planets, 183 satellites, millions of small bodies like asteroids and comets.
• Mercury, Venus, Earth and Mars are also known the inner (internal) planets.
• Jupiter, Saturn, Uranus and Neptune are called as Jovian or outer planets.
• The terrestrial planets are devoid of the condensation of the gases due to the proximity of the stars.

The Moon

• The Moon is the only natural satellite of the Earth.
• The Big Splat incident took place approximately 4.44 billion years ago.

Evolution of The Earth

• Initially, the Earth was a hot, deserted planet, whose atmosphere was sparse.
• The structure of the earth is layered. The substances that are present on the outer edge of the atmosphere to the earth’s crust are not the same.
• There are many concentric layers from the surface of the Earth to its centre.

Geological Time Scale

• The history of the Earth is divided into etc.
• The history of the earth is divided into four Eras cenzoic mesozoic paleozoic arid pre Cambrian.

Development of the lithosphere

• The planets have been formed by the accumulation of many elements. One of these planets is our Earth.
• The entire outer layer of the Earth on which the continents and oceans were formed is called the lithosphere.
• The Earth has three layers: Crust, Mantle and Core.

Comets

• Comets are the most attractive celestial bodies of our solar system.
• These stars that revolve around the Sun are solid and rocky structures.
• When they come near the Sun, due to heat, the substances and gases found in them extend to the opposite direction of the Sun and form a tail with the effect of radiation and solar winds.

Meteor

• When the asteroids come in the Earth’s gravitational perimeter, they burn up due to friction. Some meters bum up completely, while the residud part of bigger meteors strike the earth’s surface. These are called meteorites.
Meteorites are made up of many minerals. Due to their impact, large creaters are formed on earth’s surface.

Development of Atmosphere and Hydrosphere

• Development of the atmosphere has taken place due to presence of gaseous the chemical combination of indigenous gases, the formation of water vapour due to solar heat and the photosynthesis process of the biosphere.
• During the cooling and solidification of the Earth, the atmosphere formed from matter in the inner part of the Earth which came Out of the solidifying earth as gas and water vapour.
• The oceans were formed due to the accumulation of rainwater on the earth’s surface. The hydrosphere developed as a huge water reservoir.

Origin of Life

• The final stage of the origin of the earth is related to the origin of life.
• Development of life began almost 3800 million years ago on earth.
• The summary of evolution of life from unicellular bacteria to the modern man.

The Earth as a Planet Notes Important Terms

→ Earth: A living planet or the solar system on which the living beings reside. It revolvee around the sun and also rotates on its own axis. It orbits the Sun in 365-days.

→ Planetesimal: Before the origin of the planeus, small particulate substances scattered in the universe. Planets hnve been formed by coming together of planetesimals.

→ Planet: Such a celestial body in the universe that revolves around a star. The planets found in our solar system revolve around the Sun.

→ Solar-System: The Solar System (Solar family) is a group or planets, satellites, comets, asteroids and meteors that revolve around the Sun in an elliptical path.

→ Universe: The Universe is the eternal sky in which innumerable stars, planets, alms, earth and other planets, moons, meteors, asteroids, etc. are found. It is also called cosmos.

→ Insolation: The heat from the sun is called insolation. This insolation is in the form of sun rays.

→ Stars: Radiant cosmie mass made of gaseous matter is called star. They contain hydrogen 70%, helium 28%, carbon, nitrogen and neon 1.5%, and 0.05% ferrous elements. The nearest star of the Earth is the Sun.

→ Environment: The surroundings or conditions in which a person, animal or plant lives or operates.

→ Binary Theory: nhe principle related to the origin ot the Earth in which the solar family is believed to have been formed with the help of two or more than two stars.

→ Galaxy: The galaxy is a large agglomeration of innumerable stars. Each star has its own independent planetary family with it. Every galaxy rotates around ite center. There are 1010 galaxies in the universe.

→ Light Year: The distance that light travels in one year is called a light year. This distance is the large unit of measurement.

→ Nebula: Clouds of dust and gases are called nebula. According to the American astronomer GP Tupier, the creator of the Solar System is a rotating cloud made of dust and ice, i.e. the solar nebula.

→ Natural Satellite: Such natural bodies found in the universe that revolve around a planet For example: Moon (The natural satellite of the Earth).

→ Satellite: Any natural or man-made object left in the orbit of a planet, which revolves around the related body.

→ Asteroids: The small celestial rocky bodies found in between the orbits of Mars and Jupiter are called asteroids. Their size is small and shape irregular.

→ Comets: Upon reaching close to the sun, due to heat, the volatile found in them travel in a opposite direction from the Sun and form a tail. Such celestial bodies are called comets or caudal stars.

→ Terrestrial Planets: The planets that are close to the Sun including Mercury, Venus, Earth and Mars.

→ Jovian Planets: The gaseous planets Jupiter, Saturn, Uranus and Neptune, located away from the Sun.

→ Celelestial Objects: Stars, planets, moons, meteors, asteroids and planets found in the universe.

→ Equator: The imaginary line passing midway the two poles on the globe, which divides the globe into two equal parts. It is also called the 0° latitude line.

→ Continent: A continent is one of several very large landmasses of the world. Generally identified by convention rather than any strict criteria upto seven regions are commonly regarded as continents.

→ The Big Splat: The origin of the moon is due to a major collision. This collision is called ‘The Big Splat’.

→ Ocean: Huge amount of water found on the earth’s surface, where saline water is found. Around three-fourths of earth’s surface area is surrounded by them.

→ Core: The central part of the Earth in the internal structure of the Earth which extends from 2900 to 6370 km depth. It is composed of a mixture of solid and molten substances.

→ Era: The largest unit of time used in geographical time scale.

→ Period: A sub-division of the era which consists of many epochs.

→ Epoch: A sub-division of period is called the epoch.

→ Lithosphere: The upper layer of the Earth formed by the solid crust supporting the internal biosphere.

→ Crust: The topmost layer in the structure of the earth is believed to be mainly formed by silica and aluminum.

→ Outer Core: The upper part of the central layer of the earth which is present from 2900 km to 5150 km.

→ Differentiation: The process of separation of light and heavy density materials.

→ Inner Core: The lower part of the central layer of the Earth which is present from 5150 km to 6370 km. In this, the highest density of the Earth is found.

→ Comets: A comet is an icy, small celestial body that, when passing close to the sun, warms up and begins to release gases, which produces a visible atmosphere and a tail.

→ Hydrology: The branch of science concerned with the properties of the earth’s water and especially its movement in relation to land.

→ Photosynthesis: The process of building carbohydrates in the presence of water, light, chrolophyll and carbon dioxide in plants is called photosynthesis.

→ Solar wind: A large blast of gases emitted by the Sun, which travels from the Sun in all directions.

→ Volcano: A conical vent in the ground through which liquid lava, gases, water vapour and ash are emitted on the surface.

→ Degassing: The process of gases coming from the inner part of the Earth onto the surface.

→ Rain: Condensation of moisture present in the atmosphere that falls on the earth’s due to the earth’s gravity.

→ Fossil: A fossil is the hard remains of a prehistoric animal or plant that are found inside a rock.

RBSE Class 11 Geography Notes

Rajasthan Board RBSE Class 11 Geography Notes Chapter 1 Geography as a Subject

→ We live under the influence of geography till death. Every aspect of our life is associated with geography and its various components.

→ Our universe is full of mysteries in singular form or in multi-dimensional form.

→ Millions of galaxies in the cosmos have billions of stars, and planets connected with them, and clouds of dust particles and gas present a mysterious picture of the effects of gravity and other forces.

→ In this infinite universe, our galaxy is the milky way in which, there are innumerable star clusters.

→ Solar family is the group of sun, planets, satellites, meteorites, asteroids and comets.

→ Scientists believe that the age of the universe is about 14 billion years, the solar system is 10 billion years old and the earth is 4.6 billion years old.

→ Human beings came about 20 million years ago on earth.

→ Human beings have proved themselves to be the most intelligent creatures of the nature by using the resources provided by the nature according to their need and capacity.

→ Earth’s surface is the base of geography in which various variations are found.

→ Scientific geography is used to make pure and systematic analysis and logical analysis of the earth’s surface along with its variations.

→ Modern geography has evolved into an intra-disciplinary subject in which the inclusive study of physical, human and social sciences is done.

→ All these sciences have highly influenced one another.

→ The earth is a combination of lithosphere, hydrosphere, atmosphere and biosphere.

Meaning and Definition of Geography

• Geography is the word of the English language, which is inspired by the Greek language geographical terminology. Its literal meaning is ‘to describe the earth’.
• The word ‘Geographia’ was first used by the Greek scholar Eratosthenes.
• Greek and Roman scholars considered the earth to be flattened or static. It is considered spherical in ancient Indian literature.
• Geography is the science of the earth’s surface or the terrestrial science, it is studied in the context of the place and its various features/characteristics, distribution and spatial relations to the human world.
• In the nature of the subject of geography, there have been many changes from the earliest to the present.
• Geography is the science of study of the earth’s surface and it interactive relationship with humans.
• Humboldt stressed upon global systematic studies, while Reiter emphasized on regional studies of geography.
• The spread of modernity and technology has broadened and deepened the study of the earth’s surface.

Geography as a Study

• Physical and human aspects are studied in geography. On this basis, geography is divided into two branches. 1. Physical geography, 2. Human geography.
• The scope of the first branch of geography (Physical geography) is also very broad, which includes such branches as geodesy geophysics, astronomical geography, geomorphology, climatology, oceanography science, glaciology, soil geography, bioneography, medical geography, etc.
• In the second branch of geography (human geography), economic geography, agricultural geography, resource geography, transport geography, population geography, political geography, settlement geography, military geography, social geography and cultural geography, etc. have been included.
• The main purpose of geography is to contribute to the description and development of the earth in relation to human beings in a scientific way.

Physical Geography: An Introduction

• Physical geography is a major branch of geography that is rooted in facts and principles.
• Physical geography performs synthesized study of geo-physiological facts.
• The study of physical environment is the subject matter of physical geography.

Meaning and Definition of Physical Geography

• Physical geography is an important and fundamental branch of geography. This is an integrated study of many land sciences.
• In physical geography, natural variations of the inter-relation of the natural forms of lithosphere, hydrosphere, atmosphere and all the three components are explained.
• Physical geography has been defined by many scholars in different forms. In general, it can be said that the analytical study of the structural composition and inter-relationship of physical and biological environment is done in physical geography.

Nature and Scope of Physical Geography

• Earth’s surface is the center point of the study of physical geography. Not only human physical activity, but also all the components of the earth are related to the physical environment.
• In physical geography, all the three physical components are included, i.e., water, air and land. The special study of the biosphere found in all these three is also the main subject of physical geography.

Lithosphere

• The entire outer layer of the earth’s surface, on which the continents and oceans are located, is called the lithosphere.
• The lithosphere comprises the scientific history of the earth, the type of rocks, the tectonic plates, the tectonic force, the landforms, the geological process and the crustal states.

Atmosphere

• The gaseous covering spread around us is called atmosphere.
• Seasonal changes and climatic events are phenomena of the atmosphere.
• The composition, profile and height of the atmosphere, the temperature, the pressure of the wind, the direction of the wind, the form of humidity, the density of air, the origin and the type of the clouds are related to the atmosphere.

Hydrosphere

• The large water cover which is found on the earth is called hydrosphere. Physical geography is associated with the study of seas and oceans.
• The study of hydrosphere involves the study of the origin of oceans and seas, marine minerals, sea salinity, density, tides, coral reefs, waves, currents and ocean sediments.

Biosphere

• Between the ground and the atmosphere, there is a large circular belt which is the layer of soil, vegetation and organisms.
• It includes organisms, humans, animals and vegetation. It involves the study of various aspects of interpersonal relationship between the organisms and the environment.

Geography as a Subject Notes Important Terms

→ Geography: The word geography can be divided into two parts ‘geo’ and graphy. Geo comes from Greek word ‘ge’ meaning ‘Earth’ and ‘graphy’ comes from ‘graphein’ which means ‘to describe’.

→ Milky way: The earth’s galaxy is named as the Milky way.

→ Solar system: The sun’s family, i.e., the planets, the satellites, the celestial stars, the meteorites orbiting the path around the sun.

→ Planet: It is a celestial body that revolves around a star and is much smaller than that.

→ Satellite: Small astronomical objects that revolve around a planet. For example, the moon is the satellite of the Earth.

→ Asteroids: These revolve around the sun and are small cetestial bodies present in the belt between Jupiter and Mars.

→ Comets: Sometimes, in the sky, there appears a head and a tail-shaped star called a comet.

→ Meteor: Bodies made of dust and gas roaming in space, which shine brightly due to being heated up after coming into the Earth’s atmosphere.

→ Atmosphere: The gaseous enclosure in the thickness of several hundred kilometers around the earth is called atmosphere.

→ Vegetation: The grass, bushes, trees, plants found on the earth’s surface is called vegetation.

→ Resource: All such organic and inorganic matter having definite chemical composition which are used to fulfil human needs.

→ Lithosphere: The upper crust of the earth’s up to 200 kilometers deep is called the
lithosphere.

→ Hydrosphere: All water bodies located on the earth’s surface which differs from the lithosphere and atmosphere. It includes water present in the oceans, lakes, rivers, glaciers, etc.

→ Biosphere: Plants and creatures that are found on earth. It often creates a biosphere combining with hydrosphere, atmosphere and lithosphere.

→ The Moon: Earth’s natural satellite circling around the earth.

→ Human Geography: One aspect of geography in which humans and their interests or rights, human race, culture, etc. are primarily studied.

→ Climate: Long-term, average weather conditions such as temperature, rainfall, air, humidity, etc. is called the climate of a particular area.

→ Relief: The complex physical nature found on the earth’s surface (level of earth), which is divided into first, second and third relief.

→ Landform: The shape and nature of any specific terrestrial region produced by natural processes of deformation and deposition on the ground.

→ Soil: Particulate mass of inorganic rocks created due to the action of factors such as wind, water, etc. and containing organic matter, moisture, air, etc. found in any area over a long period of time.

→ Ocean: A very large aquatic part of the Earth that is filled with saline water.

→ Agriculture: The art of cultivating land to grow fruits, vegetables, crops, gardens by humaps. It also includes animal husbandry.

→ Transport: A system or means of conveying people or goods from one place to another places.

→ Communication: Exchange of facts, messages, expressions and thoughts between different places and human beings.

→ Cartography: Study of the theoretical aspects related to map composition or art.

→ Technology: Technology refers to methods, systems and devices which are the result of scientific knowledge being used for practical purposes.

→ Glacier: A dynamic, giant iceberg is called a glacier.

→ Ecology: Science that studies organisms in relation to their natural environment,
including the reaction of the organisms to the natural environment and their interactions with other organisms.

→ Population: Number of human groups or humans residing in a particular area of the ‘earth’s surface.

→ Volcano: Volcano is a rupture in the earth’s crust where from molten lava, hot ash and gases from below the Earth’s crust escape into the air.

→ Rock: The composition of the mineral particles formed from the collection of solid particles, such as the formation of the earth’s crust.

→ Endogenetic force: The force arising from the interior part of the earth, where there are horizontal or vertical movement in the earth.

→ Exogenetic force: The forces that arise or are functioning on the surface of the earth, which are always active in adjusting the surface.

→ Geomorphology: The science studying various landforms found on the earth’s surface.

→ Turbulence: Irregular and obstructed flow or motion of air or water by which the secondary vortex is produced. Cyclone is an excellent example of turbulence.

→ Ocean deposits: The marine materials which settle down on the ocean beds. Generally. The various solid/particulate matter in sea water which forms sediments on sea floor over time is called ocean deposits.

→ Coral Reef: Marine structures made from solid deposits of coral and other biological mateials, which are taller made on continental shelf, and are often immersed in sea water.

→ Rain: The amount of precipitation obtained at some place during a given time period.

→ Food chain: The series in which there is a flow of energy from the producers who make their own food. This energy is used by consumers. Decomposers are the last link of this series.

→ Sustainable Development: Sustainable development is development done without harming the environment. In this context, the current development process is determined by keeping in view the needs of the future.

RBSE Class 11 Geography Notes