Geography notes for F.6

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Geography notes for F.6

• Natural Landscape

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What is geomorphology?

• It is the study of the origin and evolution of
  landforms on the earths surface .
• Most of the earths landforms are created mainly
  by tectonic or endogenic forces (??) operating in
  the earths crust.

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Continental Drift

• Alfred Wegener,published a book on continental
  drift in 1915.
• His idea is widely accepted into the theory of
  plate tectonics

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Evidence of continental drift

• Geometric matching of continental borders
• (like jigsaw puzzle)

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• Geological evidence
• - the form and pattern of the ancient fold
  mountains
• - evidence yielded by rocks
• - belt of Mesozoic basalt (it can be find
  everywhere)

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• c) Biological evidence
• - diverse and specialised groups on various
  continental fragments

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d) Palaeoclimatic evidence (??????)

• fossils found in conditions seem impossible
• - coal was found in Antarctica

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e)Palageomagnetic evidence (????)

• - Palaeomagnetism is the study of earth
  magnetism during the geological past

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• - minerals sensitive to the magnetic field align
  themselves to the earths magnetic pole when it
  cooled and solidified

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2. Seafloor spreading

• It provide an explanation for continental drift
• mid-oceanic ridge is formed
• Evidence Heat flow with minerals, young ocean
  floor and palaeomagnetic evidence

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Examples of moving plate
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The first ship used for geological study
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Modern ship used for geological survey
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3. Plate tectonic

• It is a theory combining the concepts of
  continental drift and seafloor spreading
• It is divided into a number of plates floating
  on the asthenosphere
• Volcanic and earthquake zones are confined to the
  plate boundary
• The growth of new lithosphere below the ocean is
  balanced by the destruction of the lithosphere
  along the convergent boundaries

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Causes of plate movement

• Convection Currents
• it is fuelled by radioactive process in the
  mantle
• Difference heating in rock cause rising-sinking
  motions
• It cause a dragging force on the lithospheric
  plate

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The mechanism

• all continents once formed one supercontinent
  called PANGAEA
• (????)
• It split into Laurasian and Gondwanaland

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B Internal structure of the earth

• Earth has a diameter of 6370 km and about 40000km
  in circumference
• It consist of a solid crust (about 6km beneath
  the oceans and 35-40 km under mountains )
• A solid mantle(about 3000km thick)
• A core (solid inner core and liquid outer core)

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Materials in the earth crust
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Moho (Mohorovicic Discontinuity)(????)

• The thickness of the earth is found by a
  Yugoslavian scientists ,Andrija Mohorovicic
• It is the abrupt change (????)in density between
  the crust and the mantle
• This boundary zones averages about 10 km below
  sea level in oceans basin and and about 30 km
  beneath high mountains

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Some important terms

• The mantle is much hotter than the crust .It
  compose of mineral olivine.
• The density is 5g/cm
• The inner core is solid while the outer core is
  liquid
• Lithosphere is the crust and rigid uppermost
  parts of upper mantle,at a depth of about 100km
• Asthenosphere (???)is a zone of weaker and more
  plastic rocks and extend to 240km

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Waves

• When an earth tremor(??),primary and secondary
  waves are transmitted through the epicentre
  (??),the point at which the earthquakes occur
• Primary waves travel through solids and liquid
  while secondary waves travel through only solids

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A. Constructive plate margin

• It is a boundary where two plates move apart. A
  fissure develops,allowing hot ,molten rock to
  well up from the mantle and to from new materials
  as it solidifies,the fissure is called a
  spreading,or pull apart centre.

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Mid-oceanic ridge map by computer
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Mauna Loa in Hawwii
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Erta Ale in East Africa an active zone of rift
valley
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• Mid- Atlantic ridge is a good example
• It will cause volcanic activity, Iceland and the
  Azores
• High magnitude volcanic eruptions on and around
  the ridges,volcanic island produced

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B. Destructive plate margin

• It is a boundary where two plates collide. The
  more dense plate will normally be deflected
  beneath the less dense plate,and will be
  destroyed and absorbed at depth.
• Such action take place at the zone of subduction.
  Crumped (?????) mountain ranges,volcanoes
  earthquakes and ocean trenches (??)are found

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Andes Mountain a type of destructive plate
boundary
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Three types of collision

• Collision between oceanic plate and continential
  plate

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Collision between oceanic plates
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Collision between continental plates
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The moving path of Indian plate
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Conservative plate margin

• It is also called transform fault

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The formation of transform fault
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San Andreas fault
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Plate tectonics and Man

• The existing features of the continents and ocean
  basins are explained by the theory of plate
  tectonic
• Produce environmental hazards volcanic eruptions
  and earthquakes
• Produce mineral resources

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Ring of Fire
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Earthquakes

• Magnitude of earthquakes refer to the energy
  released at the source
• It is measured by either by Richter Scales
  (0-8logarithmic scale) (?????) or Mercalli Scales
  (12 gradations)
• There is no direct relationship between the
  magnitude and the damage caused in the earthquake
  

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Human Response to Earthquakes

• Made seismic hazard zone maps for landuse
  planning
• Man-made measure to trigger small earthquakes
• Drills and shock-proof buildings are designed
• Extensive monitoring of the earthquakes

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• Seismometers (???)are used to detect small
  earthquake
• Tiltmeters (???) and electronic distance
  measurers (?????) are used to measure the shape
  of the volcanoes
• Fertile soil is produced
• Iron,copper,zinc,lead,uranium ,etc

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Hotspot (??)
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