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Geography Unit 1 Revision (Section A: The Challenge of Natural Hazards…
Geography Unit 1 Revision
Section B: The Living World
Ecosystems
Hot Deserts
Tropical Rainforests
Section A: The Challenge of Natural Hazards
Weather Hazards
Climate Change
Tectonic Hazards
Tectonic Plates
Crust
Continental
Thicker
Less dense
Oceanic
Thinner
More dense
Are moving due to convection currents in the mantle (semi-molten rock)
Plate boundaries
Constructive
Two plates are moving away from each other
Magma rises from the mantle to fill the gap and cools, creating new crust
eg. Mid-Atantic ridge (where the North American and Eurasian plate are moving apart)
Volcanoes
Magma rises up into the gap created by plates moving apart, forming a volcano
Earthquakes
Tension builds along the cracks within plates as they move away from each other
The plates eventually jerk past each other, sending out shock waves (vibrations) which are the earthquake
Conservative
Two plates moving sideways, either in opposite directions or in the same direction at different speeds
Crust isn't created or destroyed
eg. Along the west coast of the USA
Earthquake
Tension builds up when plates that are grinding past each other get stuck
The plates eventually jerk past each other, sending out shock waves (vibrations) which are the earthquake
Destructive
Where an oceanic plate and a continental plate move towards each other
The oceanic plate subducts beneath the continental plate into the mantle and is destroyed (as it's denser)
Forms volcanoes and ocean trenches (deep sections of the ocean floor)
Volcanoes
The oceanic plate moves down into the mantle, where it's melted and destroyed
A pool of magma forms
The magma rises through cracks in the crust called vents
The magma erupts onto the surface forming a volcano
Earthquakes
Tension builds up when one plate gets stuck as it;s moving down into the mantle
The plates eventually jerk past each other, sending out shock waves (vibrations) which are the earthquake
Earthquakes
They are measured using the moment magnitude scale
Measures the amount of energy released (magnitude)
It's logarithmic - eg. magnitude 7 earthquake is 10 times more powerful than a magnitude 6 earthquake
Magnitude 6 and below only cause slight damage to buildings, although they can be worse in very built up areas
Magnitude 7 and above can cause major damage and deaths
Case Study
HIC: L'Aquila, Italy
April, 6 2009
Magnitude: 6.3
Long-term responses
New settlements were built to accommodate over 20,000 residents who used to live in the damaged city centre
Most of the city centre is being rebuilt
There have been criticisms over delays
An investigation was set up into why modern buildings weren't built to withstand earthquakes
Immediate responses
Ambulances, fire engines and the army were sent in to rescue survivors
Cranes and diggers were used to remove rubble
Camps were set up from people made homeless, providing water, food and medical care
Free mobile phones and SIM cards were provided for people who had lost their phones
Money was provided by the government to pay rent, and gas and electricity bills were suspended
Secondary effects
Fires in collapsed buildings caused more damage
Broken water pipe caused a landslide
Aftershocks hampered rescue efforts and caused more damage
Electricity and phone services were interrupted
Most were repaired within a day
Primary effects
Over 60,000 people made homeless
A bridge near the town of Fossa collapsed, and a water pipe was broken near the town of Paganica
Tens of thousands of buildings were damaged/destroyed
1,500 people injured
Around 300 deaths, mostly from collapsed buildings
LIC: Kashmir, Pakistan
October, 8 2005
Magnitude: 7.6
Secondary effects
Diarrhoea and other diseases spread due to lack of clean water
Freezing winter conditions shortly after the quake caused more casualties and meant rescue and rebuilding operations were difficult
Landslides buried buildings and people
They also blocked access roads and cut off water supplies, electricity supplies and telephone lines
Immediate responses
International aid and equipment (such as helicopters and rescue dogs) were brought in, as well as teams of people from other countries
Despite this, help didn't reach many areas for days/weeks
Many people had to be rescued by hand without equipment or help from emergency services
Tents, blankets and medical supplies were distributed
It took up to a month for them to reach most areas
Primary effects
Around 3 million people were made homeless
Hundreds of thousands of buildings were damaged/destroyed, including whole villages
Water pipelines and electricity lines were broken, cutting off supply
Tens of thousands of people were injured
Around 80,000 deaths, mostly from collapsed buildings
Long-term responses
40,000 people from one destroyed town have been relocated to a new settlement
Aid was given to rebuild schools, and government money was given to people to rebuild their homes
Many used this to buy food
After 3 years, thousands of people were still living in temporary tents
Some schools were still not rebuilt 10 years after the quake, with pupils being taught outside
The shock waves spread out from the focus
Focus - the point in the Earth where the earthquake starts
Epicentre - the point on the Earth's surface directly above the focus
Near the focus, the waves are stronger
They are found at all three plate margins
Volcanoes
Found at destructive & constructive plate margins
Some volcanoes form over parts of the mantle that are really hot (called hotspots) eg. in Hawaii
When a volcano erupts, it emits lava and gases
Some volcanoes emit lots of ash which can cover land, block out the sun and form pryoclastic flows (super-heated currents of gas, ash and rock)
Living with Tectonic Hazards
Reasons
They're confident of support from their government after an earthquake or volcanic eruption (eg. to help rebuild houses)
Don't think severe earthquake/eruption will happen
They're employed there, if people move they would have to find new jobs
Doil around volcanoes in fertile (full of minerals from volcanic ash and lava) so it makes it good for growing crops, which attracts farmers
They have always lived there (family & friends)
Volcanoes are tourist destinations so people who work in the tourist industry may live there
Management Strategies
Reduce the effects
Monitoring
Seismometers/lasers monitor earth movements
Early warning systems to give small but vital amounts of warning before an earthquake
Monitor tell-tale signs of a volcanic eruption
Tiny earthquakes, escaping gas, changes in the shape (bulges in the land where magma is rising)
Prediction
Earthquakes can't be reliably predicted
You can monitor the movement of tectonic plates, you can forecast which areas should be prepared for one
Eruptions can be predicted if the volcano is monitored
This gives people time to evacuate (reducing injuries/deaths)
Protection
Earthquake proof buildings
Using materials like reinforced concrete or building foundations that absorb an earthquake's energy
Strengthen existing buildings/bridges
Less likely to collapse
eg. by wrapping pillars in steel frames
Automatic shut-off switches that turn off gas/electricity supplies to prevent fires (if an earthquake is detected)
Planning
Future developments can be planned to avoid the areas most at risk from tectonic hazards
Emergency services training and preparation
eg. practising rescuing people from collapsed buildings/setting up shelter
Reduces the number of deaths
Education
People know what to do in an event
Plan evacuation routes
Governments can do this to get people out of dangerous areas quickly and safely
Reduces the number of people killed/injured from fires/pyroclastic flows/mudflows etc.
Emergency supplies can be stockpiled (eg. blankets/clean water/food). When a hazard is predicted, the stockpiles can be moved close to areas likely to be affected
Natural Hazards
Is a threat to people or property
Natural process which causes death, injury or disruption to humans or destroy property/possessions
Natural disaster - a natural hazard that has already happened
Extreme events that don't pose any threat to humans are not counted as hazards
Two main types
Geological Hazard
Caused by land and tectonic processes
eg. volcanoes, earthquakes, landslides, avalanches
Meteorological Hazard
Caused by weather and climate
eg. tropical storms, extreme weather (inc. heatwaves/cold spells), climate change
Risk
Factors that affect risk
Capacity to Cope
The better a population can cope with an extreme event, the lower the threat
Nature of Natural Events
Type - some hazards have a greater risk than others
Frequency - how often, increasing risk
Magnitude - how severe
Vulnerability
More people in areas exposed to natural hazards, the greater the probability they will be affected, so risk is higher
Section C: Physical Landscapes in the UK
The UK Physical Landscape
River Landscapes in the UK
Coastal Landscapes in the UK