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GEOGRAPHY
Climate ChangeClimate change is a shift in the average weather conditions that a region experiences over a long period of time.
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 15 C. This keeps the Earth warm enough for life to be ⁰sustained.
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 Collision Divergent Transform/SlidingTwo plates move into or collide into
each otherDestructive boundary
Two plates move into or collide into
each otherDestructive boundary
Two plates diverge/move away from each other as
magma spreads beneath the Earth’s
surface
Two plates slide past each other
C + O
C + C
O + O
C/O C/O
Subduction Subduction zoneOceanic TrenchFold Mountains
Subduction volcano
Fold mountains Sea floor spreadingMid-Oceanic Ridge
Transform faultEarthquakes
Nazca Plate (O) & South American
Plate (C)
Himalayan fold mountain range
Indo-Australian Plate and Eurasian Plate
Mid-Atlantic Ridge in Atlantic Ocean,
African and South American plates
St. Andreas Fault,Pacific Plate and
North American Plate
O + O
C + C
Subduction zoneOceanic 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.
Impacts of Earthquakes Collapse of infrastructure Fires Landslides Tsunamis Loss of lives Negative economic impacts Spread of diseases Trauma Disruption of jobs Impossible Fuzzy Looney Turnips Located Expensive Sleepy Televisions
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 cone-shaped volcano over time. The layers of lava build up after repeated eruptions as well as cooling and solidification to form huge cones of volcanoes.
Tourism Fertile soil Geothermal Energy Loss of Lives Pyroclastic flows: Deadly hot clouds of ash, debris, rock and dust, at
temperatures of over 400 C.⁰ 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 Thick Fairies Governed Little People Minus Delicious Hercules Equally.
Rivers and LandformsHydrological Cycle
1. Rainfall2. Groundwater3. Runoff4. Evaporation5. Transpiration6. 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, DepthDescribe river: Speed, Breadth, Depth, Volume, EnergyEnergy = Volume × Speed
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Factors affecting Speed of River
Gradient of channel Roughness of channel Wetted perimeter Gandalf Remembers Wizards
Factors affecting Volume of River
Size of drainage basin Presence of vegetation Permeability of rocks – pervious and porous Climate Desperate Visitors Paid Coins
Erosion
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
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
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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