1A: The Challenge of Natural Hazards Flashcards
What is a natural hazard?
An event that has the potential to cause damage, disruption, destruction and death
What are Tectonic Hazards?
Hazards which involve the movement of tectonic plates e.g. volcanoes
What are Atmospheric Hazards?
Hazards which involve the conditions in the air around us e.g hurricanes
What are Geomorphological Hazards?
Hazards which occur on the Earth’s surface e.g. flooding
What are Biological Hazards?
Hazards which involve living organisms e.g. forest fires
Define ‘Hazard Risk’
The chance or probability of being affected by a natural hazard
How is Deforestation a human influence which increases hazard risk?
Cutting down trees increases the risk of flooding. Trees intercept and absorb water, slowing the movement of water down
How is Urbanisation a human factor which increases hazard risk?
More people are living in urban areas therefore there is a greater risk of injury and death
How is Climate Change a human factor which increases hazard risk?
In a warmer world, the atmosphere will have more energy, leading to more intense storms and hurricanes. Climate change may cause some parts of the world to become wetter and increase the risk of flooding
How is Poverty a human factor which increases hazard risk?
In poorer parts of the world, poverty may force people to live in areas of risk and poorly constructed buildings
Describe the process of convection currents in the Earth’s mantle
- The core heats up the magma in the mantle
- The hot magma is less dense than its surroundings, so it rises upwards
- When it reaches the top, it cools
- It becomes more dense, and therefore sinks back down to the bottom
- It is heated up again, and the cycle continues
- The plates, which lie on top, are pushed and pulled by the convection currents in the magma
Compare the thickness and density of continental crust to oceanic crust
Continental crust is thicker and is less dense (cannot sink) than oceanic crust
Describe what happens at a constructive plate margin
- At a constructive plate margin, the plates are moving away from each other
- When the two plates are pulled apart, magma rises in between the gap left by the two plates separating. Lava (when magma is above ground it is classed as lava) then pours out onto the surface
- Volcanoes form in the areas where lava pours out. This lava is usually runny and free-flowing, which creates flatter volcanoes. Earthquakes also occur here as the plates shake and vibrate when they move apart
- This process can happen on continental crust or oceanic crust
-When new land is formed on the ocean floor, this is known as sea floor spreading (as the floor spreads and gets wider) - When lava cools, it forms rock. Over time, this rock builds up and can form islands, for example Iceland is a volcanic island. Iceland sits on the Mid-Atlantic ridge, which is where the lava pours out from
Describe what happens at a destructive plate margin
- The denser oceanic crust is subducted below the continental crust
- The plate that is subducting leaves a deep ocean trench
- Friction between the two plates causes strong, deep earthquakes
- The oceanic crust is melted as it is pulled deeper into the mantle, creating magma
- This magma causes pressure to build up under the crust
- Eventually the magma pushes out through weaknesses in the crust, creating explosive volcanoes
(When two continental plates meet, fold mountains are formed)
Describe what happens at a conservative plate margin
- At a conservative plate margin, parallel plates move in different directions or at different speeds in relation to each other
- When these plates move side by side, friction builds between the plates
- The friction builds up over many years, and eventually the pressure becomes so large that the plates eventually move in a sudden jolt
- This releases a lot of energy which sends vibrations through the the ground (Earthquake)
- On oceanic crust, this movement can displace a lot of water, which causes tsunamis
- On continental crust, fault lines can occur where the ground is cracked by the movement
- There are no volcanoes on conservative plate margins because no magma is being generated
Primary effects of tectonic hazards
The effects that are directly caused by the natural hazard itself. For example, people being killed or injured when an earthquake causes buildings to fall down, or lava and ash damaging infrastructure
Secondary effects of tectonic hazards
The effects that are as a result of the primary effects. For example, homelessness due to homes being destroyed or a tsunami or landslide caused by the original earthquake
Immediate responses to tectonic hazards
Actions taken as soon as the hazard happens and in its immediate aftermath. Immediate responses usually aim to reduce loss of life and provide vital aid and resources. e.g. search and rescue, food and water, shelter.
Long-term responses to tectonic hazards
Actions taken after the immediate responses when the effects of the hazard have been minimised. Long-term responses aim to restore normality and reduce risk in the future. e.g. rebuilding infrastructure and homes, building defence mechanisms, setting up warning systems
When was the Nepal earthquake?
25th April 2015
What was the magnitude of the Nepal earthquake?
7.9
How many people died in the Nepal earthquake?
9,000
How many people were injured in the Nepal earthquake?
19,000
Overall, how many people were affected by the Nepal earthquake?
Over 8 million (1/3 of Nepal’s population)
How many people were left homeless by the Nepal earthquake?
4 million
How many schools were destroyed in the Nepal earthquake?
7,000
How many shops were destroyed and how did this affect the population?
50% of the shops were destroyed, which limited food supplies in Nepal and affected people’s sources of income
How many people were in urgent need of food, water and shelter after the Nepal earthquake?
1.4 million
How did the Nepal earthquake affect utilities?
Electricity, water, sanitation and communications severely affected due to damaged and destroyed infrastructure
What was the estimated cost of the Nepal earthquake?
$5 billion USD
What were the secondary effects of the Nepal earthquake?
- Landslides and avalanches triggered
- Landslides blocked rivers like the Kali Gandaki river and flooded areas
- 17 people were killed by an avalanche at Mount Everest base camp
How did Nepal source relief supplies immediately after the earthquake?
Nepal relied heavily on international aid from areas such as China, India and the UK. These countries supplied medical support and essential suppplies
How much was raised internationally after the Nepal earthquake?
Over £87 million in donations alone
What did Nepal use for search, rescue and support?
Helicopters were used to search for survivors and reach those trapped from landslides and avalanches. They were also used for resource distribution to the cut off communities
How and why were tents so heavily relied upon after the Nepal earthquake?
Half a million tents were supplied and used for shelter for the homeless, classrooms and temporary hospitals/health care centres. Hospitals were severely overwhelmed and there were fears of more severe aftershocks causing more damage to buildings
How many people immediately fled Kathmandu after the earthquake?
300,000
How was social media used immediately after the earthquake?
Social media sites such as Facebook allowed people to mark themselves as safe and to let family members know they were out of danger
How did Nepal respond to damaged and destroyed buildings in the long-term?
In 2019, 3/4 of homes were either fully rebuilt or under repair. The government introduced stricter building codes
What issues associated with landslides did Nepal have to respond to in the long-term?
Lakes formed by landslides needed to be carefully drained and cleared so rivers could return to normal. Roads also has to be repaired after landslide damage
What were the long-term responses to Mount Everest routes?
By August 2015, base camp and the routes on Mount Everest were repaired and mountaineers could return
What happened in September 2015 that severely hindered Nepal’s recovery process?
India imposed a blockade at the order which stopped fuel, medicines and earthquake relief material from being transported to Nepal
When was the Christchurch earthquake?
22nd February 2011
How long did the Christchurch earthquake last?
10 seconds
What was the magnitude of the Christchurch earthquake?
6.3
How deep was the epicentre?
4.99km south of the centre of Christchurch
How many people were killed in the Christchurch earthquake?
185
How much damage was caused in the Christchurch earthquake in USD$?
$28 billion
What collapsed in the Christchurch earthquake?
The cathedral spire collapsed
How many people were injured as a result of the Christchurch earthquake?
3100
How many years have economists suggested it will take for New Zealand’s economy to recover? (secondary effect)
50-100 years
What fraction of the population migrated from Christchurch after the earthquake?
1/5
How many Rugby World Cup matches were cancelled as a result of the Christchurch earthquake?
5
How much international aid was immediately provided? (Christchurch earthquake)
$6-7 million
How many residents were provided with chemical toilets? (Christchurch earthquake)
30,000
How many Australian police officers flew into Christchurch three days after the earthquake?
over 300
In the long-term, how many affordable homes were constructed in Christchurch?
10,000
By when were the water and sewage restored to normal after the Christchurch earthquake?
August 2011
Why do people live near volcanoes?
- Farming: fertile soils -> more yield -> more crops to sell -> more profit -> can afford medicines/education -> higher quality of life
- Jobs in Tourism: tourists visit volcanoes for the spectacular views and relaxing hot springs - millions of jobs are created e.g. tour guides, hotel workers. The money that this brings into the economy improved quality of life
- Fatalistic Viewpoint: don’t really care and believe they will receive warning and be able to evacuate and get out of the way of any dangers
- Geothermal Energy: major source of electrical power. It is renewable energy - won’t run out, reduce greenhouse gas emissions and the likely effects of climate change
- Family Connections: family + friends live there so people don’t want to move away from communities + be lonely
- Mining: jobs are created in the mining industry. There are dangerous conditions, but a salary of $6 per day means that they continue to live and work there