GCSE Revision session.

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GCSE Revision session.

• Tectonic activity
• With Mr Thompson.

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Introduction.

• Paper 1 Physical Geography.
• Make sure you know key terms
• Make sure you know
• features,
• how they are formed,
• the effect they cause,
• advantages and disadvantages to human life.
• Human responses and that you can relate it to
  actual places.

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• This unit can be split into 3 sections. Often one
  will affects another. They are
• The earths structure.
• Volcanoes
• Earthquakes.

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The Earths structure.

• Activity 1 on the earths outline label on the
  following
• Mantle
• Outer core
• Inner core
• Crust
• Mantle
• Plates

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• The CRUST is made up of interlocking slabs of
  rock called PLATES which are moving and float on
  the MANTLE. They can be CONTINENTAL or OCEANIC

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• OCEANIC CRUST - Under the oceans, Dense (heavy),
  thin and gets destroyed at SUBDUCTION ZONES and
  created at CONSTRUCTIVE BOUNDARIES.
• CONTINENTAL CRUST - Under the continents,
  lighter, thicker and permanent.

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• PLATE MOVEMENT - caused by CONVECTION CURRENTS in
  the MANTLE.
• PLATE BOUNDARY - Where two plates meet. Most of
  the world's EARTHQUAKES and VOLCANOES are found
  on plate boundaries.

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TYPES OF PLATE BOUNDARY

• COMPRESSIONAL . Where two plates move towards
  each other. Two types-
• DESTRUCTIVE - Where oceanic crust moves towards
  continental crust and is destroyed at the
  Subduction Zone. Earthquakes and Volcanoes are
  violent and Fold Mountains are found eg West
  coast of South America where Nazca plate meets
  South American plate.

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COLLISION

• Where two Continental plates collide. Fold
  Mountains are formed. There are earthquakes, but
  no volcanoes. Eg Himalaya's

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TENSIONAL or CONSTRUCTIVE

• Where two oceanic plates move apart and new crust
  is formed. The earthquakes and volcanoes are more
  gentle. Can create a mid-ocean ridge eg The Mid
  Atlantic Ridge.

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CONSERVATIVE

• Where two plates slide past each other. Friction
  between the plates can cause pressure to build up
  that can lead to violent earthquakes when it is
  released. Eg San Andreas Fault.

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WHAT CAUSES FOLD MOUNTAINS TO BE FORMED?

• Convection currents cause two plates to move
  towards each other.
• Pressure causes a large downfold called a
  GEOSYNCLINE.
• Erosion leads to sediments being deposited in
  the geosyncline.
• Sediments build up and are compressed.
• Pressure from the moving plates cause the
  sediments to fold.
• As movements get more violent fold mountains are
  formed.

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Step 2.
Step 1.
Step 1
Step 4
Step 3.
Step 5
Step 6
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HOW DO FOLD MOUNTAINS INFLUENCE HUMAN ACTIVITY?

• ADVANTAGES
• Income from tourism eg skiing in winter and hill
  walking/climbing/mountain biking in summer.
• Hotels, Bed Breakfast, Campsites.
• Pleasant environment to live in.
• Employment in farming, forrestry HEPGrowth in
  tourism reduces out migration.

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DISADVANTAGES

• Tourism can cause increase in traffic, buildings
  which spoil the scenery, increase in house
  prices, pollution and footpath erosion.
• Difficult communications, often remote areas.
• Lack of industry for alternative employment.
• Wildlife affected

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Volcanic eruptions
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WHAT CAUSES A VOLCANIC ERUPTION?

• OCEANIC crust moves towards CONTINENTAL crust.
• The OCEANIC crust is forced under the
  CONTINENTAL CRUST
• Friction and heat from the mantle melts the
  OCEANIC crust
• MAGMA is forced upwards through weak points in
  the rock.
• Pressure build up leading to violent volcanic
  eruptions.

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Activity 2.

• Draw and lable the STRUCTURE OF A VOLCANO with
  the following
• CRATER
• ASH, BOMBS GASSES, (PYROCLASTS)
• LAVA FLOW
• MAIN VENT
• LAYERS OF ASH AND LAVA
• SECONDARY OR PARASITIC CONE
• DYKE
• EARTH'S CRUST
• MAGMA CHAMBER

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Main Vent
Crater
Ah, bombs and gases (Pyroclasts
Lava flow
Secondary or parasitic cone
Dyke
Earths crust
Layers of ash and lava
Magma chamber
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Key Phrases.

• ACTIVE VOLCANO - Erupts regularly or recently eg
  Stromboli, Montserrat, Mt. St. Helens or Mt.
  Pinatubo.
• DORMANT - Has not erupted for a long time (about
  2000 years)
• EXTINCT - Volcano that no longer erupts
• MAGMA - Molten rock that becomes LAVA when it
  reaches the surface of the earth.
• NUEE ARDENTE - A volcanic cloud of gas, steam and
  ash. E.g. eruption of Mt. St. Helens, Mt Etna or
  Montserrat.

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WHY ARE VOLCANOES DIFFERENT SHAPES?

• STEEP SIDES - Due to the lava being VISCOUS
  (thick). This lava is also known as ACID lava and
  is rich in SILICA. They are found on DESTRUCTIVE
  Plate Boundaries eg VESUVIUS. ASH volcanoes are
  also steep sided. COMPOSITE (a mixture of ash and
  lava)

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GENTLE SIDES

• Lava is NON-VISCOUS (runny) or BASIC. They are
  called SHIELD volcanoes eg MAUNA LOA (HAWAII).
  They are found on CONSTRUCTIVE Plate Boundaries.
  They are less explosive.

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A CALDERA

• A large crater caused by the top of a volcano
  being blown off or the cone collapsing into the
  VENT eg CRATER LAKE, USA.

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EFFECTS OF VOLCANOES

• SHORT TERM
• Ash falls on nearby farmland villages and towns.
  Torrential rain LAHARS and MUDFLOWS (water
  picks up huge amounts of ash).
• Ash can cause buildings to collapse eg houses,
  factories, schools hospitals.
• Lava can destroy anything in its path.
• Eruption can kill people close to the volcano.
• Roads and bridges become impassable.
• Power suppies cut off
• Water supplies contaminated

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• LONG TERM
• Crops destroyed by ash and lava and prevented new
  crops being planted.
• People forced to move away to other towns and
  cities often into shanty towns.
• People evacuated to refugee camps where diseases
  can spread very quickly.
• Farm animals killed.
• There can be long term effects on the climate eg
  delay global warming.

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WHY DO PEOPLE LIVE NEAR VOLCANOES?

• FERTILE SOIL - Volcanic ash eventually breaks
  down to form very fertile soil eg rice grown
  around Mt. Pinatubo and Vineyards Orange groves
  around Mt. Etna.

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• TOURISM - Potential income from people watching
  eruptions (eg Stromboli) or visiting dormant and
  extinct volcanoes.
• GEOTHERMAL POWER - Countries like Iceland can
  generate most of the power they need through
  geothermal energy.
• Other reasons
• People do not realise the risk of an eruption.
• In many LEDC's land is in short supply - it may
  be the only available land.
• Scientists or Vulcanologists carrying out
  research on volcanoes

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Earthquakes.
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Key words.

• FOCUS - Point in the earth's crust where the
  earthquake starts.
• EPICENTRE - Point directly above the focus on the
  surface of the earth where the damage is
  greatest.
• SEISMOGRAPH - Instrument that measures the
  strength of the shockwaves.
• RICHTER SCALE - Scale used to measure an
  earthquake by the strength of its shockwaves.
• MERCALI SCALE - A way of measuring the strength
  of an earthquake by the damage it does.
• SHOCKWAVES -Movements in the earth's crust
  caused by the earthquake.
• AFTERSHOCKS - Smaller shockwaves that follow the
  main earthquake.

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EFFECTS OF EARTHQUAKES

• SHORT TERM
• People killed and injured.
• Old buildings not built to withstand earthquakes
  collapsed.
• People made homeless
• Huge fires caused by broken gas pipes
• Buildings weakened by original earthquake
  destroyed by aftershocks.
• People die due to disease, shock and hypothermia
• Liquefaction where ground becomes like quick
  sand.
• Fire service unable to control fires due to lack
  of water caused by broken mains.

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LONG TERM

• Communication links destroyed
• Employment lost due to destruction of factories
  e.g. Kobe 2 Toyota factories.
• Kobe's port severely disrupted.Damage estimated
  to cost 80 billion
• Areas still without services for periods of 12
  months and more.

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HOW DO PEOPLE RESPOND TO EARTHQUAKES AND
VOLCANOES?

• They build buildings that are strengthened with
  steel to withstand earthquakes. They are designed
  to sway.
• They avoid building on clay and sand.
• In Japan there are now monitors that will stop
  the railways, turn off the gas as soon as the
  primary waves are felt.
• By mapping previous earthquakes and plotting the
  regularity of earthquakes it is possible to
  estimate when the next earthquake may strike.
• By monitoring earth movements and gas emissions
  it is possible to forecast volcanic eruptions eg
  Mt. Pinatubo in the Phillipines.
• Emergency planning eg in Japan where they hold a
  Disaster Day when everyone practices what to do
  if an earthquake strikes. There are simulators
  where people can experience an earthquake.
  Posters telling people what to do in an
  earthquake.

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WHY ARE MORE PEOPLE LIKELY TO DIE IN LEDC's THAN
IN MEDC's?

• Less medical and relief support available.
• Poorer communications often mean that access to
  affected areas is more difficult.
• Housing is often of poorer construction, more
  likely to collapse or catch fire.
• Lack of money to provide instruments or
  technology to predict disasters or limit there
  effects.
• Poorer medical and emergency services and lack
  of emergency equipment.
• Many people in LEDC's are subsistence farmers
  and if their crops are destroyed they have
  nothing else.
• Power and water supplies may be disrupted
  allowing disease to break out and spread quickly.

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Case studies.

• MEDCs Kobe Californa
• LEDCs - Iran

Iran
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Two earthquakes compared.
California
Iran
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Location Bam in Iran
Date 26 December, 2003
Strength of earthquake on the Richter scale 6.6
Number dead 28,000
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Location California in USA
Date 22 December, 2003
Strength of earthquake on the Richter scale 6.5
Number dead 28,000
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Here are some other reasons why the earthquake in
Iran was so bad

• The houses in Iraq were badly built. They were
  made from mud brick which collapsed straight
  away.
• When mud brick collapses it disintegrates.
• This leaves less air pockets, which might have
  allowed some people to survive, even though they
  were trapped.

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The time of day when the earthquake happened was
also important. In Bam, it happened at 5 oclock
on a Friday morning. Friday is the Muslim day of
rest. Where do you think most people were, and
why did they die?
These are like the mud brick buildings that
collapsed in Bam
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Buildings like this in a rich country might
topple, but they dont crumble. What would be
your chance of survival in this situation?
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Other things to consider