Here is an article looking into Geography GCSE such as the Earth crust, tectonic plates, hotspots, composite and shield volcanoes, primary and secondary impacts of volcanic eruptions, how to predict volcanic eruptions, how earthquakes occur, Richter scale, primary and secondary impacts of earthquakes, a look into earthquake proof MEDC and LEDC building, climate change, natural causes of climate change, dinosaur extinction, why greenhouse gases are rising, consequences of climate change, why it is hard to predict future levels of greenhouse gases and factors that affect distribution of different. As you can see, there is a lot of content so feel free to skip to the part of the article most relevant to you.
Earth Crust
- The Earth has crust: oceanic and continental crust which is both solid
- Oceanic crust is dense, basaltic and thin (6-8km)
- Continental crust is less dense, granite and thick (25-80km)
- Both types of crust have temperatures up to 900 degrees Celsius
Mantle
- Outer mantle is partially molten and made of peridotites. It’s temperatures are up to 1,600 degrees Celsius
- Inner mantle is solid and made up of silica base minerals. It’s temperatures are up to 4,000 degrees Celsius
The core of the Earth is liquid, made up of iron and nickel and has temperatures up to 5,000 degrees Celsius.
- Constructive plate boundary – Mid Atlantic ridge, Iceland (North American Plate ß] [à Eurasian Plate) CAUSES VOLCANOES.
- Collision plate boundary – Himalayas (Indian Plate à ß Eurasian Plate) CAUSES EARTHQUAKES/ FOLD MOUNTAINS.
- Conservative plate boundary – San Andreas Fault, San Fransisco (one plate sliding diagonally up, the other diagonally down) CAUSES EARTHQUAKES.
- Destructive plate boundary – The Andes, (one plate slides horizontally, the other diagonally down and happens with the South American and Nazca plate) CAUSES FOLD MOUNTAINS/EARTHQUAKES.
Why do tectonic plates move?
- Radioactive decay in the core is a heat source
- This drives convection currents in the mantle
- Magma rises and cools then falls back down and cycle starts again
- The convection currents slowly drag tectonic plates
- Tectonic plates move at a few millimetres per year
Plumes are parts of convection cells where heat moves towards the surface. They create concentrated zones of heat and bring magma to the surface. If the magma breaks through the crust it erupts as lava in a volcano. Some plumes form constructive plate boundaries and some form hotspots.
Hotspots are isolated columns of hot material rising in the mantle which are created by convection plumes in the mantle. They are a location for volcanoes e.g. Hawaii’s Mauna Loa.
The Earth has a magnetic field created by the flow of minerals such as iron from the core. It protects us from harmful radiation in space and from the sun.
Volcanos do not have to consist of being on land either. Submarine volcanos are volcanos underneath the surface of the sea.
Composite Volcano: Mount St. Helens, USA:
- Made from alternate layers of ash and lava
- Basaltic and granitic magma is thick and viscous à explodes à slow to move so cools and forms steep sides
- Produces Pyroclastic flows and ash bombs
Form at destructive plate boundaries where:
- Oceanic crust made out of basalt which is denser is sub-ducted beneath the continental crust which is granitic
- As oceanic crust sinks temperature increases and it melts
- The molten rock rises up towards the Earth’s surface and forms the volcano
Shield Volcano: Mauna Loa, Hawaii:
- Magma is basaltic and fluid à produces large rivers of lava, no explosion à moves fast so gently sloping sides
- Erupt frequently and gently
Form at hotspots:
- Earth’s crust is thin and lies over a large magma chamber
- Magma breaks through crust and forms volcano
- Not near a plate boundary
Impacts of Volcanic Eruptions
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Primary impacts of volcanic eruptions
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Secondary impacts of volcanic eruptions
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Ash clouds: Impacts aviation. Remember ash cloud in Iceland when we were in Egypt for the summer.
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Lake overturn- volcanic vibrations cause carbon dioxide to rise from the bottom of lakes nearby suffocating wildlife, livestock and humans.
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Ash- Affects breathing, respiratory problems, can collapse roofs, good for faming as it acts as a fertiliser
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Landslides/ Avalanches
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Pyroclastic flow- hot clouds of ash and rock that travel 250mph and 200 degrees Celsius; can destroy whole villages
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Boulders- destroy buildings and kill people
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Lava- burns houses, starts forest fires à
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Homelessness and animals lose habitats
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Lahar- dormant volcano which has turned into a lake erupts causing hot water, ash and rocks to flow out of the volcano and submerge surrounding areas
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We can predict volcanic eruptions using:
- Seismology – Looking for vibrations and/or swelling and inflation.
- Analysing composition of volcano – Greater amount of gases being released à greater amount of magma. If sulphur dioxide levels increase the volcano is likely to erupt in a matter of days.
Volcanic Eruption Facts
Volcanic Eruption LEDC: Mount Nyragongo, The Republic of Congo- Composite:
- 100 deaths, poisonous gas + trapped in lava
- 400,000 evacuated
- Lava rush à Earthquakes à Destroyed homes à 120,000 homeless
- Old men and women could not escape when fissures opened up and lava spewed out
Volcanic Eruption MEDC: Mt. St Helens (May 1980)- Composite:
- 57 deaths
- Thousands of Elk, Deer and Salmon were killed and crops were destroyed
- Roads closed due to low visibility from the ash
- Some airports closed for two weeks
Volcanic Eruption Disaster Management:
- BLESS The Concrete Ground
- Boreholes- measure water temperature as magma heats it up
- Lava bomb shelters
- Evacuation signs and drills
- Seismometer- monitor vibrations
- Satellites- monitor swelling
- Tilt meters- monitor swelling
- Concrete lahar tunnels- divert dangerous mud flows
- Gas/Lava samples
Earthquakes occur when:
- Plates begin to move past each other
- Tension and pressure builds up as plates continue to move
- Plates suddenly jolt with a lot of force
- Energy is released as they move further and this is when people feel the earthquake
Richter scale: Numerical scale for expressing the magnitude of an earthquake based on seismic oscillations.
Impacts of Earthquakes
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Primary impacts of earthquakes
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Secondary impacts of earthquakes
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Buildings collapse including houses so people become homeless
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Fires start because of damage done to infrastructure
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People die as they are trapped in the rubble
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Disrupts transport; train tracks are moved which will cost money to fix meaning that some people will find it hard to get about
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Bodies stuck in rubble start decomposing and cause disease
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Overpasses fall so delays and deaths
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Environmental refugees
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Disrupted roads and train tracks lead to deaths
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Lots of money needs to be spent on rebuilding
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- 240,000 dead
- 1 million left destitute
- Decaying bodies à Disease
- Tourism (main income) declined
- India, Japan, Australia, and America (AIJA) formed to coordinate the relief effort
Earthquakes:
- LEDC- El Salvador Earthquake 2001
- Over 1 thousand deaths
- Over 8 thousand injuries
- 1/5 of houses destroyed
- ~ 25% of population homeless
- 1/6 of annual GDP to rebuild and recover
Why:
- Five major earthquakes in 6 weeks à no time to recover
- Landslides
- Clean water and sanitation issues
- Buildings not designed to withstand earthquakes
- No water supply for fire engines to use
- No good roads to reach areas in need
- Airport was closed à hard to transport relief to where it was needed quickly
MEDC- San Francisco Earthquake 1989:
- 57 deaths
- Over 8 thousand injuries
- People made homeless
Why:
- Collapsed buildings and damaged gas pipes
- Bay Bridge collapse
- Double Decker Freeway collapse
- Soil liquefaction damaged property
- Good disaster management plan
- Buildings earthquake proof
- Earthquake focus deeper underground
- Roads and hospitals unaffected
Earthquake Proof Buildings
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Earthquake proof MEDC building
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Earthquake proof LEDC building
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Damper acts as a pendulum reduce swaying of building
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Light thatch roof
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Cross Bracing prevents floor collapse
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Walls made of mud and straw packed between wooden slats
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Strong Steel Frame flexible stop cracking
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Simple steel rod foundations
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Deep Foundations prevent collapse
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Concrete rings tie the walls to the foundation
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Double Glazed Windows stop broken glass shower down
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Cross braced wood or bamboo frame
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Gas supplies automatically shut off to reduce fire risk
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Shock absorbers built into cross bracing
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Climate and Change
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Air Mass
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Polar Maritime
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Arctic Maritime
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Polar Continental Maritime
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Tropical Continental Air Mass
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Tropical Maritime
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From
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Greenland/ Arctic sea
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Arctic
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Central Europe
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North Africa
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Atlantic
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Weather caused
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Cold showery weather
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Snow in winter
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Hot air- dry summer
Cold air- snowy winter
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Hot, dry air- hot summers
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Cloud, rain and mild weather
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We know that climate has changed a lot in the past as:
- Fossils are found of animals and plants in places they are not found in today
- Evidence of glaciation in regions now free of ice
- Evidence from rocks show us what climate was like when they were formed
- Evidence from ice cores in Greenland and Antarctica show us how much carbon dioxide and oxygen was in the atmosphere when the ice formed
Natural causes of Climate Change:
- Volcanic Eruptions- Ash, dust and gas block solar radiation à Earth cools BUT volcanoes release carbon dioxide and sulphur dioxide hence can make the Earth heat up
- Sunspots- Dark areas, sign of greater solar activity, ~11 year cycles, Little Ice Age little sunspots observed
- Changes in Earth’s orbit and rotation-Milankovitch said ~100,000 years earth orbit changes from circular elliptical + axis changes in 41,000 and 21,000 cycles à affects how much solar energy earth receives- more solar energy higher temp, lower solar energy lower temp
Little Ice Age:
- 90 earthquakes – ash blocked sunlight à drop in amount of energy the earth received which led to a drop in global temperature
- Fishing poor as migrated to warmer waters
- Parasites devastated crops
- Population decline; Iceland ½ population dies
- Price of grain increased social unrest/revolt
- Travel difficult
- Boats could not supply villages with essentials as water froze
- Ice fairs on the Thames
Dinosaur extinction:
- Meteor struck the Earth
- Produced a lot of gas and ash which
- Decreased amount of sunlight Earth received
- Hence plants died
- Hence herbivores dinos died
- Hence carnivores dinos died
- End of ice age à sudden temperature rise of 5 degrees – animals could not cope with climate change
- Retreating glaciers à less water for plants à plants died à herbivores died à carnivores died
- Human beings hunted them to extinction
Enhanced greenhouse effect:
- Short wave radiation from sun passes through the atmosphere
- Some long wave radiation passes back into space
- Some long wave radiation is reflected off greenhouse gasses back to the earth à warms up
Why is amount of greenhouse gasses rising?
- Deforestation à trees are not able to make oxygen out of carbon dioxide since being cut down
- Rice farming à methane
- Demand for beef à methane
- Transport
- Burning fossil fuels for energy
MEDCs are more responsible, as well as countries with a large population and lots of industrial areas e.g. America and China.
So why is global warming such a big deal?
- Permafrost melts à greenhouse gasses released
- 1/3 of Bangladesh underwater AND other island nations
- Millions of environmental refugees
- Antarctica and Arctic and Greenland glaciers melt
- Food shortages as soil dries out
- Polar bears in Arctic die
- Coral reefs destroyed
Consequences of Climate Change:
- MEDC-UK: Tropical insects, air conditioning, No Scottish ski resorts, floods, heat waves Summer- more heat waves, droughts, less rain Winter- warmer, more rain, less snow, more storms.
- LEDC- Egypt: Desertification, Nile delta flood, Water War, Alexandria flooded.
Why is it hard to predict future levels of greenhouse gases?
- Hard to predict people’s reactions- will they reduce the pollution they release?
- Cannot predict huge volcanic eruptions which may neutralise or increase CO2 levels
- Cannot predict population size
Battle For The Biosphere
Rainforests are located on and around the equator between the tropic of cancer and the tropic of Capricorn.
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Factors that affect distribution of different biomes
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How?
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Temperature
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Affects the length of growing season
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Precipitation
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Affects distribution of rain throughout the year
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Sunlight
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Determines amount of light available for photosynthesis
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Humidity
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Controls rates of evapotranspiration
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Latitude
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The position of a place north or south of the equator expressed in degrees
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Altitude
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The height of something above sea level expressed in meters. Temperatures drop to around 1/5 degree for every 100m increase in altitude
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