NCERT Geography Notes PDF

CHAPTER 5: MINERALS AND ROCKS Minerals found in the crust are in solid form whereas in interior they are in liquid form. Mineral: naturally occurring inorganic substance having an orderly atomic structure and a definite chemical composition and physical properties. It is composed of two or three m...

CHAPTER 5: MINERALS AND ROCKS Minerals found in the crust are in solid form whereas in interior they are in liquid form. Mineral: naturally occurring inorganic substance having an orderly atomic structure and a definite chemical composition and physical properties. It is composed of two or three minerals /single element ex. S, Cu, Ag, Au, Graphite. The basic source of all minerals is the hot magma in the interior of the earth. Coal, petroleum and natural gas are organic minerals. PHYSICAL CHARACTERISTICS OF MINERALS 1. EXTERNAL CRYSTAL FORM: Internal arrangement of molecules. 2. CLEAVAGE: Tendency to break in given directions producing relatively plane surfaces. 3. FRACTURE: crystal will break in irregular manner. 4. LUSTURE: Appearance of material w/o regards to color. 5. COLOUR: Some minerals have characteristics colors determined by molecular structure. 6. Transparency: refers to the degree to which light can pass through a mineral. 7. STRUCTURE: particular arrangement of the individual crystals fine medium, or coarse 8. HARDNESS: Relative resistance being scratched Ex Talc is softest while Diamond is hardest. 9. SPECIFIC GRAVITY: The ratio between the weight of a given object and the weight of an equal volume of water. IMPORTANT MINERALS OF THE EARTH CRUST 1. FELDSPAR: Silicon & Oxygen Are Common Elements in feldspar. 2. QUARTZ: important component of sand granite. Consists of silica. 3. PYROXENE: consists of calcium, aluminum, magnesium, iron, silica. 4. OLIVINE: Magnesium, Iron, Silica are major elements 5. AMPHIOLE: aluminum, calcium silica, iron, magnesium are major element. 6. MICA: consists of potassium, aluminum, magnesium iron silica Type of Rock Rocks are aggregate of one or more minerals, they may be hard or soft in varied colors, they do not have definite chemical composition. Petrology is the science of rocks. IGNEOUS ROCKS: 1. They are primary rocks 2. Formed due to cooling of lava 3. They are two types intrusive & extrusive rocks. Extrusive rocks have small grains because of sudden cooling intrusive rocks have bigger grains due to slow cooling 4. They are hard 5. Do not contain fossils 6. Do not allow water to percolate through them 7. No layers SEDIMENTARY ROCKS: 1. 1. Formed Due to Sedimentation 2. 2. Consists Of Layers 3. 3. Contain Fossils 4. 4. The Process of Sedimentary Rock Formation Is Called Lithification 5. 5. They Are Three Types. A. Mechanically Formed B. Chemically Formed C. Organically Formed. METAMORPHIC ROCKS: 1. 1. Formed Due to Recrystallization 2. 2. Formed Due to Pressure and Temperature 3. 3. Very Smooth 4. 4. Consists of layers sometimes very precious stones A diagram of the rock cycle: 1. 1 = magma; 2. 2 = crystallization (freezing of rock); 3. 3 = igneous rocks; 4. 4 = erosion; 5. 5 = sedimentation; 6. 6 = sediments sedimentary rocks;  7. 7 = tectonic burial and metamorphism; 8. 8 = metamorphic rocks; 9. 9 = melting. CHAPTER 6: GEOMORPHIC PROCESSES The endogenic and exogenic forces cause physical stress and chemical actions on the earth material and bring the changes in the configuration of the earth surface is called GEOMORPHIC PROCESSES. Diastrophism and volcanism are Endogenic processes. Weathering, Mass wasting, Erosion & Deposition Are Exogenic Processes. ENDOGENIC PROCESS: the energy generating from within the earth is the main force behind the endogenic geomorphic processes. The energy generated due to 1. Radioactivity 2. Rotational Force 3. Tidal Friction 4. Primordial Heat from The Origin of the Earth. DIASTROPHISM: All process that move, elevate or build up portions of the earth's crust. THEY INCLUDE 1. OROGENIC PROCESSES: mountain building through folding 2. EPEROGENIC PROCESS: uplifting large part of earth crust 3. EARTH QUAKES 4. PLATE TECTONICS VOLCANISM: Movement of molten rock towards the earth's surface and also formation of many intrusive and extrusive volcanic forms. EXOGENIC PROCESSES: They derive their energy from atmosphere determined by the prime source the sun and also gradients created by the tectonic factors. All the exogenic process are covered under general term DENUDATION. WEATHERING: it is the action of elements of weather on earth materials. 1. CHEMICAL WEATHERING PROCESSES: A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them. 2. PHYSICAL WEATHERING PROCESSES: Factors Influencing the Physical Weathering 1. Gravitational Force Overburden Pressure, Load And Shearing Stress 2. Expansion Forces Due  to Temperature Changes, Crystal Growth or Animal Activity 3. Water Pressures Controlled by Wetting and Drying Cycles. They are mostly due to thermal expansion, and pressure release. 3. BIOLOGICAL WEATHERING: Removal or contribution of ions to the environment due to biological activity is called biological weathering. Burrowing and wedging by organism like earthworks termites, rodents help in exposing the new surfaces to chemical attack. MASS MOVEMENT: these movements transfer the mass of rock debris down the slopes under the direct influence of gravity. The mass movements can be grouped into three types 1. Slow movements Ex: Creep, Solifluction 2. Rapid movements Ex: MUD FLOW, EARTH FLOW, DEBRIS AVALANCHES 3. Land slide Ex: SLUMP, DEBRIS SLIDE, ROCK FALL Reasons for landslides along the Himalayas 1. Tectonically active 2. Made of sedimentary rocks 3. Steep slopes 4. Heavy rains 5. Unconsolidated material is found. EROSION AND DEPOSITION Erosion involves acquisition and transportation of rock debris. Weathering, mass wasting, and erosion are degradational processes. SOIL FORMATION: Soil is the collection natural b and supporting or capable of supporting plants. PROCESS OF SOIL FORMATION: weathering is basic process for soil formation. SOIL FORMING FACTORS:1. Parent material 2. Topography 3. Climate 4. Biological activity. 5.Time Rhizobium is the bacteria fix the nitrogen in the soil and live in the roots of legum plants. CHAPTER 7: LANDFORMS AND THEIR EVOLUTION Land form: small to medium tracts or parcels of the earth's surface are called landforms. Various geomorphic agents bring the changes to the landforms such as running water, moving ice, wind glaciers, underground water, waves by erosion and deposition. Factors influencing erosion: 1. Rock structures such as fold, fault, joints, fractures, hardness, softness permeability, and impermeability 2. Stability of sea level 3. Tectonic stability of landmass 4. Climate. RUNNING WATER 1. In humid regions rainfall is heavy so running water is dominant agent 2. There are two components of running water A. OVERLAND FLOW CAUSES SHEET EROSION B. LINEAR FLOW CAUSES STREAM EROSION Stages of the river  YOUTH - 1. Less Streams 2. Less Integration 3. V-shaped Valleys Are Common 4. Stream Divides Are Swampy Marshy Areas 5. Water Falls and Rapids Are Common MATURE - 1. More Streams 2. More Integration of Streams 3. Deep V-shaped Valleys 4.Wider Flood Plains 5. Meanders Are Present 6. Rapids And Water Falls Disappear OLD - 1. Smaller Tributaries 2. Few In Number 3. Flood Plains Are Common 4. Natural Leaves and Oxbow Lakes Are Also Present 5. Most Of the Landscape Is Just Above Sea Level. EROSIONAL AND DEPOSITIONAL LANDFORMS BY RUNNING WATER EROSIONAL LANDFORMS - V SHAPED VALLEY, GORGE, CANYON, POT HOLES, PLUNGE POOLS, INCISED MEANDERS, RIVER TERRACES GORGE - 1. steep sides 2. equal width of top and bottom 3. small in length 4. they are found in semi-arid lands. CANYON - 1. Step like sides 2. wider at the top and narrow at the bottom 3. Longer in length 4. Found in dry areas ex. Grand Canyon POT HOLES: 1. They are circular depressions 2. formed by abrasion 3. pebbles and boulders get collected in these holes and rotated and make depression wider and deep PLUNGE POOLS: 1. Found at Foot of the Water Falls 2. Formed Due to Soft Rocks 3. They Are Below the Level of River Bed MEANDERS 1. Lateral erosion is common in the lower course of the rivers 2. Due to low kinetic energy water is changing its course 3. Generally found in the flood plains RIVER TERRACES : 1. Marking old valley floor 2. They represent flood plain levels 3. They may consist of stream deposits 4. They are formed due to vertical erosion DEPOSITIONAL LANDFORMS ALLUVIAL FANS, DELTAS, FLOOD PALINS, NATURAL LEEVES, POINT BARS, OXBOW LAKES, MEANDERS, BRAIDED CHANNEL ALLUVIAL FANS 1. Found near the foot of the hills 2. The river break into number of channels 3. Low gradient 4. Coarse load is deposited DELTAS 1. Found near by the mouth of the river 2. Made of fine alluvial soils FLOOD PLAINS: Major landforms in the river deposition 2.big boulders are deposited first and then fine material is carried to the longer distance. NATURAL LEEVES: associated with flood plains. Found along the flood plains of large rivers. They are low linear, parallel ridges made of coarse material found along the river bank. POINT BARS: they are also called as meander bars. 2.found along the convex side of meanders of large rivers. They are uniform in profile. MEANDERS: loop like channels are called meanders. it is not a landform it is a type of river channel. OXBOW LAKES: Found along the river bank on the convex side of the meander. Convex side is deposited and concave side is eroded. BRAIDED CHANNEL: When rivers carry coarse material, there can be selective deposition of coarser materials causing formation of a central bar, which diverts the flow towards the banks; and this flow increases lateral erosion on the banks.  EROSIONAL AND DEPOSITIONAL LANDFORMS BY GROUND WATER KARST TOPOGRAPHY : Any limestone or dolomitic region showing typical landforms produced by the action of groundwater through the processes of solution and deposition is called Karst topography. EROSIONAL LANDFORMS - Pools, Sinkholes, Lapies, Limestone Pavements and Caves Sinkholes are very common in limestone/karst areas. A sinkhole is an opening more or less circular at the top and funnel-shaped towards the bottom. The term doline is sometimes used to refer the collapse sinks. When sinkholes and dolines join because of slumping of materials along their margins or due to roof collapse of caves, long, narrow to wide trenches called valley sinks or Uvalas form. Gradually, most of the surface of the limestone is eaten away leaving it extremely irregular ridges or lapies. DEPOSITIONAL LANDFORMS - Stalactites, Stalagmites and Pillars Stalactites hang as icicles. broad at their bases and taper towards the free ends. Stalagmites rise up from the floor of the caves. The stalagmite and stalactites eventually fuse to give rise to columns and pillars. EROSIONAL AND DEPOSITIONAL LANDFORMS BY GLACIERS EROSIONAL LANDFORMS Cirque, Horns and Serrated Ridges, Glacial Valleys/Troughs Cirques quite often are found at the heads of glacial valleys.They are deep, long and wide troughs. DEPOSITIONAL LANDFORMS- MORAINS, Eskers, Outwash Plains, Drumlins MORAINS - They are long ridges of deposits of glacial till. Eskers - Eskers are ridges made of sands and gravels, deposited by glacial meltwater flowing through tunnels within and underneath glaciers, or through meltwater channels on top of glaciers. Outwash Plains - a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. Drumlins - Drumlins are oval-shaped hills, largely composed of glacial drift, formed beneath a glacier or ice sheet and aligned in the direction of ice flow. EROSIONAL AND DEPOSITIONAL LANDFORMS BY WAVES & CURRENT EROSIONAL LANDFORMS - Cliffs, Terraces, Caves and Stacks DEPOSITIONAL LANDFORMS - Beaches and Dunes; Bars, Barriers and Spits  EROSIONAL AND DEPOSITIONAL LANDFORMS BY WINDS EROSIONAL LANDFORMS - Pediments and Pedi plains; Playas; Deflation Hollows and Caves; Mushroom, Table and Pedestal Rocks PEDIMENTS - evolution in deserts, A pediment develops when sheets of running water wash over it in intense water. PEDI PALIN - Pedi plain is a broad and relatively flat rock surface formed by the joining of several pediments. PLAYAS A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappeared due to evaporation DEPOSITIONAL LANDFORMS - Beaches and Dunes; Bars, Barriers and Spits, Barchans Crescent shaped dunes called barchans. Seif is similar to barchan with a small difference. Seif has only one wing or point. This happens when there is shift in wind conditions.