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

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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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