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You are here: Home / Geography / G C Leong Summary

G C Leong Summary

May 2, 2020 by BureaucratONE Leave a Comment Last Updated May 2, 2020

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Table of Contents hide
1 THE EARTH AND THE UNIVERSE
2 THE EARTH'S CRUST
3 VOLCANISM AND EARTHQUAKES
4 WEATHERING, MASS MOVEMENT AND GROUNDWATER
5 LANDFORMS MADE BY RUNNING WATER
6 LANDFORMS OF GLACIATION
7 ARID OR DESERT LANDFORMS
8 LIMESTONE AND CHALK LANDFORM
9 LAKES
10 COASTAL LANDFORMS

THE EARTH AND THE UNIVERSE

  • EXPLORING THE UNIVERSE
    • Stars occur in clusters known as galaxies or nebulas
    • Light takes 6 seconds to reach earth from moon and 8min 2 sec from sun and nearest star 4 years
  • The solar system
    • All planets revolve in elliptical orbit
    • Surface temp of sun is 6000*C and 20 million*C in the interior
    • Sun is 3 lakh times as big as earth
    • Mercury is smallest planet and takes 88 day to revolve the sun
    • Venus is the Earth's twin because of size, mass and density
    • Mars next planet after earth to have life
    • Jupiter is the largest planet
      • 12 satellite
      • Dark and light circular bands
    • Saturn
      • 3 rings and 9 satellites
      • 2nd largest
    • Uranus
      • 50 times larger and 15 times heavier than earth
      • Only clockwise orbiting  planet
    • Neptune
  • The shape of Earth
    • Geoid or earth-shaped
  • Evidence of the Earth's Sphericity
    • Circum-navigation of the earth
    • The circular horizon
    • Ship's visibility - Increasing altitude widens circular horizon and mast before ship
    • Sunrise and sunset
    • The lunar eclipse
    • Planetary bodies are spherical
    • Driving poles on level ground on a curved earth - 8 inches/mile
    • Ariel photographs
  • Earth's Movement
    • Rotates on own axis in west to east - 24 hr
    • Revolves at 18.5 miles per second 365.25 days
    • Varying lengths of day and night
      • 66 1/2* inclination
      • In summer artic circle - Land of midnight sun - 24 hrs sunlight
      • 6 months continuous daylight in poles 
  • The altitude of the Midday sun
    • Vertically overhead at the equator called equinoxes meaning equal nights
      • 21 March - spring equinox
      • 21 September - autumn equinox
  • Seasonal changes and their effects on temperature
    • Summer - sun higher in the sky and days are longer so net gain
    • Winter - oblique rays and net loss
  • Dawn and Twilight
    • Due to diffused and diffracted light
    • In equator it is short because sun is sets and rise in vertical path
    • In poles and temperate sun is oblique so dawn and twilight is long
  • Mathematical location of places on the globe
    • Intersection of latitude and longitude is the co-ordinates
    • Latitude - angular distance of an point on the earth's surface, measured in degrees from the centre of the earth and is parallel to equator
      • 1* , 60', 60''
      • Distance between two latitude is 111Km or 60 miles
      • Tropics
        • Cancer - 23 1/2°N
        • Capricorn - 23 1/2°S
        • Antarctic circle - 66 1/2°S
        • Arctic circle - 66 1/2°N
    • Longitude - angular distance measure along the equator east or west of Prime meridian
      • Royal astronomical observatory at Greenwich near London is Prime meridian
      • 15° - 1 hour
      • 1° - 4 minutes
      • Indian Standard time 5 hr 30 min - 82.5°
  • International date time
    • East to west - gain a day
    • West to east - lose a day

THE EARTH'S CRUST

  • The structure of the earth
    • Lithosphere
      • Upper
        • Granitic rocks
        • Forms continental crust
        • SIAL
        • Density - 2.7
      • Lower
        • Basaltic
        • Oceanic crust
        • SIMA
        • Density - 3
        • SIAL floats on SIMA
    • Moho discontinuity
    • Asthenosphere
    • Mantle
      • a.k.a Mesosphere
      • Dense rocks rich in OLIVINE
      • 2850 Km
    • Gutenburg Discontinuity
    • Core - 3470 Km
      • Outer Core - Liquid
        • 2200 Km
      • Inner Core - Solid
        • 1270 km
      • a.k.a Barysphere
      • NIFE
    • Hydrosphere
      • Part of crust filled with water
    • Atmosphere
  • The Classification of Rocks
    • Igneous
      • Fossil is not found
      • Cooling and solidification of molten rock magma
      • Crystalline structure
      • Sub division based on mineral composition
        • High Silica - acidic/lighter/less dense/granite
        • Oxides of fe, al, mg - basic/dense/darker/
      • Sub division based on origin
        • Plutonic rocks
          • Slowly solidified beneath so large crystal - granite, diorite, gabbro
        • Volcanic
          • Solidified rapidly outside so small crystal - hard and resistant/ basaltic
          • Eg.antrim of northern Ireland, deccan plateau in India, Columbia-snake plateau
    • Sedimentary
      • Layer and stratified rocks
      • Fossil is found
      • Division based on origin
        • Mechanically formed sedimentary rocks
          • Sandstones by sand grains and quartz fragments
          • Conglomerate - rounded pebbles
          • Breccia - angular pebbles
          • Shale or mudstone - clay
        • Organically formed
          • Remains of living organism like corals or shellfish
          • Calcareous like chalk and limestone
          • Carbonaceous like peat, lignite or coal
        • Chemically formed
          • Rock salt
          • Gypsum or calcium sulphate or potash or nitrates
    • Metamorphic
      • Due to heat and pressure caused by intense earth movement
      • Clay into slate
      • limestone into marble
      • Sandstone into quartzite
      • Granite into gneiss
      • Shale into schist
      • Coat into graphite
    • Earth movements and major landforms
      • Caldonian folds - oldest - scandinavia, scotland
      • Hercynian folds - urals, welsh, harz, appalachians
      • Young alpine - alps, himalayas, andes and rockies
    • Types of mountains
      • Fold mountains
        • Himalayas, Rockies, Andes and Alps
        • Anticline(up) & syncline(down)<overfold<recumbent fold<nappe over thrust plane or fault line
        • A.k.a mountains of elevation
        • Volcanic activity
        • Rich minerals like tin, copper, gold and petroleum
      • Block mountains
        •  horsts or block mountain
        • Graben or rift valley
        • Hunsruck mountains, vosges and black forest of rhineland, east african rift valley
      • Volcanic mountains
        • A.k.a mountains of accumulation
        • Mt.Fuji of japan, Mt.Mayon of Phhilippines, Mt.Merapi of sumatra, Mt.Agung of Bali and Mt.catopaxi of Ecuador
      • Residual mountain
        • Mt.Mandnock in USA, Highlands of scotland, scandinavia and deccan plateau
        • A.k.a mountain of denudation
    • Types of Plateaux
      •  elevated uplands with extensive level surface and usually descend steeply to the surrounding lowland
      • A.k.a tablelands
      • Tectonic plateaux
        • caused by earth movements
        • Continental blocks like deccan plateau
        • Tilted plateau - meseta if central Iberia
        • Faulted like Harz of Germany
        • Enclosed by fold mountains - intermont plateaux like Tibetan plateau between Himalayan and kunlun / Bolivian plateau between andes range - Highest and extensive
      • Volcanic plateaux
        • Antrim plateau of Northern Ireland and north western deccan plateau
        • Columbia snake plateau 
      • Dissected plateaux
        • Scottish highlands
        • Humid highlands, glaciation, drier areas
        • Mesas and buttes
    • Types of plains
      • Area of lowland that is either level or undulating
      • Most fertile and occupied
      • Indo-Gangetic plain, Mississippi plain, Yang-tze plain
      • Grasslands of Russian steppers, the north american praries and argentinian pampas
      • Structural Plain
        • Structurally depressed
        • Russian platform, great plains of USA, central lowlands of Australia
      • Depositional Plain
        • alluvial, flood, delta plain
          • Nile delta, ganges, Hang Ho
        • Outwash plain
          • Not fertile
          • Unsorted fluvio-glacial sands and gravels
        • Till plain or drift plain
          • Fertile
          • Boulder clay
        • Coastal plain
        • Loess plain
          • Aeolian deposits or very fine dust
      • Erosional plain
        • Plains of denudation
        • Peneplains or almost plains
        • Ice-scored plains
        • Pediments or Pediplains and inselberg

VOLCANISM AND EARTHQUAKES

  • Landforms of Igneous rocks
    • Sill and Dykes
      • Commonest
      • Sill - horizontal - e.g Great Whin Sill
      • Dykes - vertical - e.g cleveland dyke and kaula lampur
    • Liths
      • Larger size
      • Loccolith
        • Large blister or dome shaped
        • Level base with pipe like conduit from below
        • Henry mountain in USA
      • Lopolith
        • Saucer shape
        • Bushveld lopolith in Transvaal
      • Phacolith
        • Lens shaped
        • Anticline or syncline
        • Fed by conduit from below
        • Condon Hill in Shropshire, England
      • Batholith
        • Granite
        • Huge
        • Wicklow Mountains of Ireland, Uplands of Britanny,France and Main range of Malaysia
  • Origin of volcanoes
    • Crustal disturbances
      • Basic lavas
        • Hottest
        • Highly fluid
        • Dark coloured like Basalt
        • Rich in iron and Magnesium
        • Not very explosive and flows quietly
        • Shield or dome volcanoes
      • Acid Lava
        • Highly vicious
        • Light coloured
        • Silica rich
        • Loud explosion as rapid congealing in vents
        • Forms spine or plug - Mt.Pelee in Martinique and Puy de dome of france
  • Types of volcanoes
    • Active, dormant and extinct  - Mt.Vsusvius and Mt.Krakatau once thought extinct
  • Extrusive landforms
    • Lava plains and basalt plateaux - snake Basin, USA
    • Lava domes and shield volcanoes - Hawaii Mauna Loa and Kilauea
    • Caldera - eruptions weakens structure and blows of top and forms a depression
    • Crater - smaller caldera
    • Ash and cinder cones
    • Composite cones or strato volcanoes
      • Highest and most common
      • Parasitic cones and subsidiary crater
  • Geysers and Hot springs
    • Geysers
      • Volcanic region
      • Upto 150 feet
      • Explosive
      • 3 major areas - Iceland, the rotorua district of north island and yellow stone national park
      • Old faithful erupts every 63 minutes in yellow stone national park
    • Hot springs
      • Common
      • Not explosive
      • Contains minerals
      • Heated by interior forces
      • Iceland, hawaii, japan
  • The distribution of earthquake
    • Circum pacific areas with epicentres - 70%
    • Mediterranean-Himalayan belt -20%
       

WEATHERING, MASS MOVEMENT AND GROUNDWATER

  • Internal forces - Constructive (orogenesis)
  • External forces destructive (denudation) - 4 phases
    • Weathering
      • Chemical - felspar(easily weathered), quartz and mica of granite
        • Regolith - mineral remains of decomposed rocks
        • enhanced in underlying rocks
        • 3 process
          • Solution - most potent
          • Oxidation - iron content
          • Decomposition of organic acids - acids
      • Mechanical or physical
        • Repeated temp changes
        • Onion peeling or exfoliation of rounded boulders
      • Repeated wetting and drying
      • Frost action
        • Frost shattered peaks
      • Biotic factor
        • Roots
  • Mass Movement
    • Weathered material due to gravity
    • Soil creep
      • Gradual
      • Common in damp - water lubricates soil particles
    • Soil flow or solifluction
      • Arid region during rain
      • Frozen under ground during spring
      • Big-bursts in Ireland
    • Landslide
      • Rapid
      • Steel slopes
      • Earthquakes or volcanic disturbances
      • Lubricating action of rain
      • Slumping - permeable layer over non-permeable layer like clay
  • Ground water
    • Porous rocks - sand stone
    • Permeable and porous - sand stone
    • Non permeable but porous - clay
    • Permeable and non-porous -granite
  • Water table
    • Permeable rock that stores water is aquifer
    • Karst region - limestone - vauclusian spring
  • Erosion
  • Transportation
  • Deposition

LANDFORMS MADE BY RUNNING WATER

  • The development of a river system
    • Rain fall
      • Evaporated
      • Seepage
      • Runoff - causes denundation or general lowering of the earth's surface
        • Rivulets
        • Brooks
        • Streams
        • Tributaries
    • Sources of river
      • Lake
      • Marsh
      • Upland and catchment areas
        • Crest of mountains - divide or watershed
        • Initial stream consequence of slope is consequent stream
        • Consequent streams are joined by tributaries either obliquely or right angles
        • Homogenous beds of uniform resistance - tributaries obliquely as insequent stream
        • Consequent stream + insequent stream = dendritic drainage pattern or tree-like 
        • Rocks with alternate hard and soft rocks - tributaries join as subsequent stream at right angle
        • Consequent stream + subsequent stream = trellised or rectangular drainage
  • The mechanism of Humid Erosion
    • Mass movement due to lubricating action and gravity
    • Not Steep = slow + soil creep
    • Steep = sudden + landslide
  • The process of river action
    • River load
      • Material in solution - dissolved solution
      • Material in suspension - sand, silt and mud
      • The traction load - pebbles, rocks and boulders
  • River erosion and Transportation
    • Corrasion or abrasion - mechanical grinding of traction load on banks and beds
      • Lateral corrasion - widens V-Valley
      • Vertical Corrasion - deepens
    • Corrosion or solution - chemical or solvent
      • Calcium carbonate in limestones
    • Hydraulic action - Mechanical loosening and sweeping by water itself
    • Attrition - wear and tear of transported material themselves
  • The course of a River
    • The upper or mountain course or youth stage
      • Predominantly erosion
      • Source of river
      • Swift
      • Vertical corrasion
      • Deep, narrow and deep V shaped valley
      • Very resistant rocks - lateral corrasion is absent - gorges(indus is kashmir) and canyons(Bryce in USA)
      • Features
        • River capture - river piracy or river beheading
          • Back cutting or headwards erosion into divide
          • Elbow of capture
          • Beheaded stream is called misfit
          • Valley below elbow is wind gap
          • E.g - Irrawaddy captured Upper sittang, Northumberland, North tyne
        • Rapids, cataracts and waterfalls
          • Uneven resistance - rapids or jump or fall down stream
          • Cataracts - greater rapid
          • Waterfall - greater cataract - forms lunge pool beneath
    • The middle or valley course or mature stage
      • Lateral corrasion replaces vertical corrasion
      • Predominantly transports sediments
      • Features
        • Meanders
        • (concave)River cliff and (convex)slip-off slopes(shingle deposition)
        • Interlocking spurs
    • The lower or plain course or old age
      • Vertical corrasion ceases and lateral continues
      • Predominantly deposition
      • Braided streams
      • Features
        • Flood plains
          • Levees and artificial embankment
          • Hwang-Ho china's sorrow
        • Ox-Bow lakes or mortlake or dead lake
          •  cut-off or bayous in Mississippi basin
          • Meander is more pronounced
        • Delta
          • River reaches sea and drops fine material at the mouth
          • Fan-shaped alluvial area called delta
          • Actually seaward extension of flood plane
          • Due to obstruction caused by alluvium river discharges its water through distributaries
          • Delta extends over time
          • E.g - Mississippi has birds -foot delta, Nile,ganges and Mekong has fan-shaped delta
          • Amazon, ob and vistula estuarine deltas, ebro of spain  has tooth like projection called cuspate delta
          • Conditions for delta
            • Active erosion
            • Tideless and sheltered coast
            • No large lake to filter sediments
            •  no strong current perpendicular to rive mouth
    • River rejuvenation
      • Being young again
      • -ve movement -When land uplifts or sea level falls
      • Active down-cutting
      • Leaves behind terraces
      • Knick point or rejuvenated head
      • Deepening of gorges and deep valley with entrenched or incised  meanders
      • +ive movement - depression of land and rise in sea level -ice melting
  • The human aspects of rivers
    • Navigation
    •  Boundary

LANDFORMS OF GLACIATION

  • Pleistocene - 30,000 years ago ice sheets over entire temperate region
  • Today only Greenland and Antarctica
  • Ice shelves break into ice bergs
  • Nunataks - peaks of mountain projects above surface
  • Repeated melting and freezing of snow forms hard granular neve or firn
  • Glacier river of ice
  • Glaciers flow in tongue shape - greatest rate of movement in middle
  • Glaciers converge to form an extensive ice-mass called a piedmont glacier. E.g malaspina glacier
  • LANDFORMS OF HIGHLAND GLACIATION
    • Glacier erodes by plucking and abrasion
    • All glaciated floors have striation or scratching
    • Rock flour
    • Features
      • Corrie, cirque or cwm
      • Aretes and pyramidal peaks
      • Bergschrund
      • U-Shaped glacial trough
      • Hanging valleys
      • Rock basins and rock steps
      • Moraines
    • Landform of Glaciated Lowlands
      • Roche Moutonnee
      • Crag and Tail
      • Boulder clay or glacial till
      • Erratics
      • Drumlins
      • Eskers
      • Terminal Moraines
      • Outwash plains
    • The Human aspects of Glaciated Landforms

ARID OR DESERT LANDFORMS

  • Types
    • Hamada or rocky desert
    • Reg or stony desert
    • Erg or sandy desert
    • Badlands
    • Mountain deserts
  • The Mechanism of Arid Erosion
    • Weathering
    • Actions of wind in deserts
      • Deflation
      • Abrasion
      • Attrition
  • Landforms of Wind Erosion in Deserts
    • Rock  pedestals or mushroom rocks
    • Zeugen
    • Yardangs
    • Mesas and buttes
    • Inselberg
    • Ventifacts or dreikanter
    • Deflation hollows
  • Landforms of wind Deposition in Deserts
    • Dunes
      • Barchan
      • Seifs or longitudinal dunes
    • Loess
  • Landforms due to Water Action in deserts

LIMESTONE AND CHALK LANDFORM

  • Limestone and chalk
  • Characteristic Features of a Karst Region

LAKES

  • THE FORMATION AND ORIGIN OF LAKES
    • Lakes formed by earth movements
      • Tectonic lakes
      • Rift valley lakes
    • Lakes formed by Glaciation
      • Cirque lakes or tarns
      • Kettle lakes
      • Rock-hollow lakes
      • Lakes due to morainic damming of valleys
      • Lakes due to the deposition of glacial drifts
    • Lakes formed by Volcanic Activity
      • Crater and caldera lakes
      • Lava-blocked lakes
      • Lakes due to subsidence of a volcanic land surface
    • Lakes formed by erosion
      • Karst lakes
      • Wind-deflated lakes
    • Lakes formed by Deposition
      • Lakes due to river deposits
      • Lakes due to Marine deposits
      • Lakes due to landslides, screes and avalanches
    • Lakes formed by Human and Biological Activity
      • Man-made lakes
      • Lakes made by animals
      • Other types of lakes
    • Lakes and Man
      • Communication
      • Economic and industrial development
      • Water storage
      • Hydro-electric power generation
      • Regulating river flows
      • Moderation of climate
      • Source of food
      • Source of minerals
      • Tourist attraction and health resorts

COASTAL LANDFORMS

  • The action of waves, tides and currents
    • Zone of erosion - area between the low water level and high water level
    • Swash and backwash
  • The mechanism of Marine Erosion
    • Corrasion - debris erode the base
    • Attrition - against each other
    • Hydraulic action - water into joints
    • Solvent action - limestone coasts
  • Coastal feature of Erosion
    • Capes and bays
      • softer rocks - inlets, coves or bays
      • Harder rocks - headlands, promontories and capes
    • Cliffs and wave cut platforms(eroded base) - notch becomes big and eroded material settles in off-shore terrace
      • Strata dipping seaward - easily eroded
      • Strata dipping landward - resistant 
    • Cave, arch, stack and stump
      • Caves - local weakness
      • Arch - two caves
      • Stack - eroded arch
      • Stump - further eroded stack
    • Geos and gloups
      • Gloups are blow-holes of caves
      • Geos - enlarged gloups
  • Costal feature of Deposition
    • Beaches
    • Spits and bars
    • Marine dunes and dune Belts
  • Types of coasts
    • Coastlines of submergence
    • Coastlines of emergence
      • Ria coasts
      • Fiord coasts
      • Dalmatian coast
      • Estuarine coast
    • Coastlines of Emergence
      • Uplifted lowland coast
      • Emergent upland coast

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