1. What is a natural hazard?
Section A-Challenges of Natural Hazards
Natural Hazards
Plate Boundaries
2 plates slide past each other, this can be in different directions or both going in the same direction but at different speeds. No crust is either formed or destroyed here so volcanoes do not occur. The plates moving past each other get struck, pressure builds until one slips triggering an earthquake.
What is a natural hazard?
Natural hazards are sudden, severe event which make the natural environment difficult for humans to manage.
They are a hazard if they posse a risk to people but are not classed as a hazard if they happen where people do not live
Where they cause high levels of death, injury and damage they become known as disasters.
Weather hazards are known as atmospheric hazards.
Earthquakes and Volcanic eruptions are known as geological hazards
2 plates move towards each other. The Oceanic crust is heavier than the continental so it subducts (goes down) into the mantle. The movement causes earthquakes. The oceanic crusts begins to melt in the mantle and becomes magma, this will then rise forming a violent eruption from composite volcanoes.
Hazard Risk
Hazard risk means the chance of being affected by a natural hazard. For example if you live on the San Andreas Fault line you are more at risk from earthquakes.
What other factors lead to risk?
2 plates move apart. Most occur under the oceans. As the plates move apart magma rises and forms volcanoes called shields. Volcanic islands (Iceland) are formed here as well.
Urbanisation: Densely-populated means more risk by building on unstable ground
Climate Change:
It rises sea levels and causes extreme weather
Poverty:
Poorly built housing/buildings fall down easier
Farming:
Fertile soil found on floodplains where it floods

2. Distribution of volcanoes and earthquakes
Plate Tectonics
Distribution of volcanoes and earthquakes
The crust is broken into huge slabs called plates. These plates move very slowly. One theory of how they move is convection current. As the semi-molten rock in the mantle is heated it becomes less dense than its surroundings and rises. As it reaches the crust above, it spreads out carrying the plates above with it. As the semi-molten rock then cools, it gradually sinks back down to be re-heated (see diagram below).
Continental drift is a theory supported by plate movement. Wegener stated that we were once a supercontinent called Pangaea. If you look at a map it looks like S. America and Africa were joined together like a jigsaw puzzle
Volcanoes and earthquakes are mainly found where 2 or more plates meet. They occur in clusters and form a linear formation as can be seen along the west coast of S. America. Around the edge of the Pacific Ocean many active volcanoes can be located and this is why it is known as the “ring of fire”.

3. Earthquake example-HIC Earthquake example-LIC
Maule, Chile, 2010 (HIC)
27th February – Magnitude 8.8
Primary Effects
Secondary Effects
500 people died.
12000 people injured.
homes, 4500 schools, 56 hospitals and 53 ports destroyed.
1500km of roads damaged by landslides – remote communicates cut off
Coastal towns hit by tsunami waves.
A fire at a chemical plant near Santiago.
Immediate Responses
Long-term Responses
Emergency services arrived quickly.
Temporary repairs made to Route 5 North-South highway made in 24 hours.
Within 10 days 90% home had water and power restored.
$60 million raised.
One month later, gov. launched rehousing plan to help households.
Economy could be rebuilt based on copper exports rather than international aid.
Take up to 4 years to fully recover.
Gorka, Nepal, 2015 (LIC)
25th April – Magnitude 7.9
Primary Effects
Secondary Effects
8841 people died.
16800 people injured.
7000 schools, 26 hospitals and Daharahara Tower (heritage site) destroyed.
3 million homeless.
Avalanche in Langstang left 250 missing.
Landslide blocked Kali Gandaki river – risk of flooding.
Immediate Responses
Long-term Responses
International help requested.
Helicopters rescued people on Mt. Everest.
500, 000 tents provided.
Field hospitals set up.
Free telephone calls.
Lakes and valleys cleared of landslide material to avoid flooding.
Stricter building controls enforced.
New trekking routes opened on Mt. Everest and permits extended.
$247 aid money raised.

4. Why live in tectonic areas?
3 P’s
People live close to volcanoes because Geothermal energy can be harnessed by using the steam from underground which has been heated by the Earth’s magma. This steam is used to drive turbines in geothermal power stations to produce electricity for domestic and industrial use. Countries such as Iceland and New Zealand use this method of generating electricity.
Protection is used in both HICs and LICs. In countries like Japan and USA strong building with reinforced concrete are constructed. Many have cross braces to make them stronger. Deep foundations to help keep them upright and seismic isolators which are huge springs to enable the building to move with the tremors. In Peru houses are made with bamboo as this is a flexible material.
Prediction is not an accurate science at present. Seismometers are used in areas that are known to have tectonic activity to record and gather evidence. Tiltmeters are used at volcanoes to look for changes in shape and movement.
Tourism is another reason as people are employed in this industry as tourist flock to see attractions such as the “Blue Lagoon” in Iceland or Pompeii in Italy.
Planning is carried out in many countries. Here people practise what they need to do if earthquakes strike. On the 1st September each year Japan hold a national earthquake training day.
Farming is a main source of employment in volcanic areas. The ash from volcanic eruptions has made the soil fertile and good for growing crops. The step slopes are terraced to make farming easier.