Transcript GCSE Revision session.

GCSE Revision session.
Tectonic activity
With Mr Thompson.
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.
• This unit can be split into 3 sections. Often
one will affects another. They are:
• The earths structure.
• Volcanoes
• Earthquakes.
The Earths structure.
• Activity 1 on the earths outline label on the
following:
• Mantle
• Outer core
• Inner core
• Crust
• Mantle
• Plates
• 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
• 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.
• 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.
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.
COLLISION
• Where two Continental plates collide. Fold
Mountains are formed. There are
earthquakes, but no volcanoes. Eg
Himalaya's
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.
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.
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.
Step 2.
Step 1.
Step 1
Step
4
Step 3.
Step 5
Step 6
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.
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
Volcanic eruptions
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.
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
Crater
Main Vent
Ah, bombs and
gases
(Pyroclasts
Lava flow
Secondary or
parasitic cone
Dyke
Earths crust
Layers of ash
and lava
Magma
chamber
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.
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)
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.
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.
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
• 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.
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.
• 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
Earthquakes.
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.
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.
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.
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.
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.
Case studies.
• MEDC’s – Kobe &
Californa
• LEDC’s - Iran
Iran
Two earthquakes compared.
California
Iran
Location: Bam in Iran
Date: 26 December, 2003
Strength of earthquake on the Richter scale: 6.6
Number dead: 28,000
Location: California in USA
Date: 22 December, 2003
Strength of earthquake on the Richter scale: 6.5
Number dead: 28,000
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.
The time of day when the earthquake happened
was also important.
In Bam, it happened at 5 o’clock 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
Buildings like this in a rich country might topple, but they
don’t crumble. What would be your chance of survival in
this situation?
Other things to consider: