GEOGRAPHY
Climate Change
Climate change is a shift in the average weather conditions that a region experiences
over a long period of time.
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Enhanced greenhouse effect  Global Warming
The greenhouse effect is a natural process whereby greenhouse gases absorb heat
from the Sun’s rays and trap it in the atmosphere. These gases, namely carbon
dioxide, water vapour, nitrous oxides and methane, help to maintain the Earth’s
average temperature at around 15⁰C. This keeps the Earth warm enough for life to be
sustained.
With an increase in human activities, more greenhouse gases are released and trapped
in the atmosphere. This has created an enhanced greenhouse effect. This causes a
rise in the Earth’s average global temperature known as global warming.
Causes of global warming:
Industrial Revolution in early 18th century, Industrial activities, large-scale
deforestation and agricultural activities are the main causes of increase of
greenhouse gases in the atmosphere.
Rapid increase of fossil fuel use has led to high levels of CO2 and NO3 being released
into the atmosphere. Chlorofluorocarbons (CFCs) also contributes.
Large-scale deforestation and forest fires have reduced the amount of vegetation
cover on the Earth’s surface. Forests are cleared for timber and mining, and to create
land for other activities such as agriculture and urban redevelopment. Trees and plants
take in CO2 and release oxygen through photosynthesis. When more trees are
removed from the environment, less CO2 is absorbed from the atmosphere, thus CO2
levels in the atmosphere decrease.
Wet rice cultivation and cattle ranching release methane and nitrous oxides.
Effects of global warming:
Melting ice and rising sea levels make low-lying coastal countries are especially
vulnerable to rising sea levels.
Extreme weather conditions
- higher relative humidity increases evaporation rates, increasing rainfall and causing
floods
- warmer ocean temp. cause more intense tropical storms to form
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- high temperatures increase evaporation rates, causing lakes and rivers to dry up
quickly. less water vapour in atmosphere, thus less rain, causing heat waves and
droughts
Reducing the impact of climate change:
Mitigation: Reducing emissions of greenhouse gases.
Adaptation: Preparing for possible effects of global warming, e.g. relocating people
away from low-lying coastal areas
Plate Tectonics
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Types of plate boundaries
Convergent
Two plates move
into or collide into
each other
Destructive
boundary
Collision
Two plates move
into or collide into
each other
Destructive
boundary
C+O
C+C
 
 
Subduction
Subduction zone
Oceanic Trench
Fold Mountains
Subduction volcano
Fold mountains
Nazca Plate (O) &
South American
Plate (C)
Himalayan fold
mountain range
Indo-Australian Plate
and Eurasian Plate
O+O
Divergent
Two plates
diverge/move away
from each other as
magma spreads
beneath the Earth’s
surface
Transform/Sliding
Two plates slide
past each other
O+O
 
Sea floor spreading
Mid-Oceanic Ridge
C/O C/O

Transform fault
Earthquakes
Mid-Atlantic Ridge in
Atlantic Ocean,
African and South
American plates
St. Andreas Fault,
Pacific Plate and
North American Plate
C+C
 
 
Subduction zone
Oceanic Trench
Undersea
volcano
volcanic islands
Rift-valley/
sea
Mariana Islands in
the Pacific Ocean
East African Rift
Valley/
Red Sea
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Landforms and Processes

Convergent Plate Boundary
Subduction: When two crusts collide, the denser oceanic crust will be forced under the
less dense crust, into the mantle, forming an oceanic trench. [The denser oceanic
trench is denser than the continental crust because the minerals that make up the
oceanic crust have higher densities than those in the continental crust.] [One oceanic
crust is denser than the other due to the age of the sea floor.] Partial melting of oceanic
plate caused by pressure and heat causes formation of magma. (Subduction zone)
Subduction volcanoes: Some of the magma will rise up through fractures in fractures
in the crust in the subduction zone, forming subduction volcanoes.
Oceanic-Oceanic Convergence
Volcanic islands: Over time, these volcanoes may build up and rise above sea level to
form volcanic islands.
Oceanic-Continental Convergence
Fold mountains: The compression of the continental crust causes the crust to buckle,
forming a fold mountain range.

Collision Plate Boundary
Fold mountain range: When both continental plates collide, neither sinks because their
densities are similar. Massive bending and folding of the crust takes place, forming a
fold mountain range.

Divergent Plate Boundary
Oceanic-Oceanic Divergence
Mid-oceanic ridge: When the plates diverge, magma rises to fill the gap that is created
at the plate boundary. The magma cools and solidifies to create new sea floors which
extend the existing sea floors, forming a mid-oceanic ridge.
Continental-Continental Divergence
Rift valleys: As the continental crusts diverge, they are stretched, causing fractures to
appear at the boundary. The land between the two crusts sinks as a result of the
divergent movement, and the linear depression formed is called a rift valley.

Transform Plate Boundary
Transform Fault: Great amount of stress, but little volcanic activity and earthquakes
are common
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Earthquakes
Earthquakes are sudden vibrations of the Earth’s crust as a result of plate movements.
At sliding boundaries, the crust experiences enormous stress and the rocks are forced
to bend. Stress is gradually built up, until the rock snaps and breaks along a fault line,
releasing the stress in seismic waves, causing the plates to vibrate violently and thus
causing an earthquake.
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Impacts of Earthquakes
Collapse of infrastructure
Fires
Landslides
Tsunamis
Loss of lives
Negative economic impacts
Spread of diseases
Trauma
Disruption of jobs
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Joyously.
Volcanoes
Volcanoes are formed when high temperatures and pressure in the mantle cause the
magma to rise upwards and gather at the magma chamber. When the pressure in the
magma chamber becomes too great, the magma escapes through cracks in the Earth’s
surface.
Magma will become lava after it erupts out of the Earth’s crust. Much of this lava after it
erupts out of the Earth’s crust. Much of this lava solidifies near the vent, forming a coneshaped volcano over time. The layers of lava build up after repeated eruptions as well
as cooling and solidification to form huge cones of volcanoes.
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Tourism
Fertile soil
Geothermal Energy
Loss of Lives
Pyroclastic flows: Deadly hot clouds of ash, debris, rock and dust, at
temperatures of over 400⁰C.
Mudflows: Heavy rainfall after and during the eruption may cause rainwater to
be saturated with volcanic ash and debris, becoming highly fluid and flowing
down slops at great velocity and spreading across great distances. Mudflows
cause massive destruction and loss of many lives.
Destruction of land
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Health hazards: Gas leaks; ash and release of toxic gases cause respiratory
problems
Economic costs: Disruption to air travel; tourism; trade
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Rivers and Landforms
Hydrological Cycle
1.
2.
3.
4.
5.
6.
Rainfall
Groundwater
Runoff
Evaporation
Transpiration
Condensation
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River System
1. Upper course:
River channel
small, shallow, narrow
rough  presence of large stones in the channel from vertical erosion
Vertical erosion bc high speed  downward-cutting and valley-deepening
Most of the energy used to overcome friction with rough channel, thus little energy for
erosion
River valley
V-shaped: deep, narrow, steep-sided
Gradient
steep slope  fast and powerful river flow
Volume
small volume of water  few tributaries
2. Middle course:
River channel
wider and deeper
lateral erosion  valley-widening
River valley
wide V-shape and wider floor
Gradient
not as steep as upper course, gentler slopes
Volume
greater volume  more tributaries, eroded materials transported
3. Lower course
River channel
widest and deepest  lateral erosion
most of the energy used for transportation, then deposition of sediments
flooding occurs regularly
River valley
broad, flat valleys
Gradient
very gentle  slow-moving river resulting in high level of deposition
Volume
greater volume  more tributaries
Describe valley: Slope, Breadth, Depth
Describe river: Speed, Breadth, Depth, Volume, Energy
Energy = Volume × Speed
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Factors affecting Speed of River
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Gradient of channel
Roughness of channel
Wetted perimeter
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Factors affecting Volume of River
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Size of drainage basin
Presence of vegetation
Permeability of rocks – pervious and porous
Climate
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Erosion
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C.A.S.H.
Corrasion/Abrasion
 rocks dragged along river bed or against banks
 grinding action causes river channel to widen and
deepen as rocks and soil are scraped off
Attrition  Eroded materials (rock fragments) constantly collide with each other
as they move
 Larger materials are broken down, load carried by river is eroded
Solution  Rain reacts with carbon dioxide to form carbonic acid
 Carbonic acid dissolves minerals in rocks on river bed and banks
and carried away in solution
Hydraulic action  Force of fast-flowing water loosens rocks and soil along
banks and bed
 Rocks and soil are dislodged and carried down river
Transportation
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T.S.S.S.
Traction  Boulders and stones roll or slide along river bed downstream
Saltation  Smaller materials (e.g. coarse sand) are lifted up and dropped on
the river bed over and over again, moving downstream in bouncing motions
Suspension  Finer particles (e.g. silt, clay, sand) are carried along river
without touching the river bed
Solution  Dissolved minerals and materials are transported downstream by
running water
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Landforms
Waterfalls
 Erosion of rocks of different resistance:
River flow; Difference in erosion; waterfall + plunge pool + headward retreat
 Faulting:
River flows along fault line; waterfall over difference in height over fault; plunge pool +
corrosion + headward retreat
Meanders
Loops in river course (middle & lower) formed by erosion, transportation, deposition
Outer bank: less friction, high speed, more energy, more erosion, undercut
 river cliff (steep-sided bank)
Sediments and transported and deposited along inner bank
Inner bank: more friction, lower speed, deposition occurs  slip-off slope (water
becomes shallower, gentle slope formed)
Asymmetrical channel
Ox-bow lake
 Pronounced meander: erosion & deposition, slip-off slope & river cliff;
 Cut-off: neck of land breached, straight river, cut-off (abandoned meander loop);
 Oxbow Lake: deposition sealing off oxbow lake from river channel
River Vocabulary
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Drainage basin/ Catchment area – area of land drained by river
Watershed – edge of highland surrounding drainage basin, marks boundary
between 2 drainage basins
Source – beginning or start of river (usually in mountains)
Confluence – point at which 2 rivers or streams join
Tributary – stream/ smaller river joining a larger stream/ river
Mouth – point at which river ends, usually entering a sea
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