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Revision Guide The Challenge of Natural

Hazards Tectonic hazards.

Paper 1 section A

21st May 2019

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A) Tectonic Hazards:

What are natural hazards?

The Factors that affects hazard risk

A natural hazard is a threat (whether natural or human) that has the potential to cause loss of life, injury, property damage, socio-economic disruption or environmental degradation.

What are the different types of natural hazard?

• Volcanic eruptions • Earthquakes • Storms • Tsunami • Landslides • Floods • Avalanche

What is a tectonic hazard? A natural hazard caused by the movement of tectonic plates (including volcanoes and earthquakes)

Why do some people live in areas that are at risk from hazards? • Advantages often out weight the disadvantages for people who choose to live in a hazardous

region. Advantages include geothermal energy and fertile soils if living in an active volcanic zone. Volcanoes are also popular tourist destinations so jobs and income can be provided by living near to a volcano.

• Sometimes people have little choice of where they live or knowledge that where they are loving is dangerous

• Some people don’t ever consider moving either as this is where their family has always lived • Volcanoes and earthquakes happen rarely. • People can prepare and protect from earthquake hazards

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What is plate tectonics theory?

Where do volcanoes and earthquakes happen?

The Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates. These are constantly moving at a few centimetres each year. Over millions of years the movement allows whole continents to shift thousands of kilometres apart. This process is called continental drift. The plates move because of convection currents in the Earth's mantle. These are driven by the heat produced by the inner core which pushes up hot molten rock through the mantle. When this reaches the crust, this hot rock spreads, pulling the plates a part (or together). This magma then cools, and sinks back down.

Where do earthquakes and volcanic eruptions occur? • The majority are found along plate boundaries • Earthquake are found in linear clusters along boundaries • A minority of earthquakes occur away from boundaries which could be as a

result of human activity such as underground mining or oil extraction. • Some volcanoes occur away from boundaries where magma pushes through

the crust itself • There is a large number of earthquakes and volcanoes found

around the pacific plate (commonly known as the Pacific Ring of Fire) • Volcanoes form at both constructive and destructive plate boundaries • Earthquakes form at all three boundaries: Constructive, destructive and

conservative

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Destructive plate boundaries/margins

Constructive plate boundaries/margins

How do volcanoes occur at destructive plate boundaries? 1. Two plates, a continental and an oceanic

move towards each other, driven by convection currents in the mantle

2. When they meet, the denser oceanic plate is subducted (pushed under/sinks)

3. As it sinks high temperatures in the mantle cause the oceanic crust to melt and turn into magma

4. This magma rises up through cracks and weaknesses in the crust

5. When magma reaches the surface is cools and hardens to form a volcano

How do earthquakes occur at destructive plate boundaries? 1. Two plates, a continental and an oceanic move

towards each other, driven by convection currents in the mantle

2. When they meet, the denser oceanic plate is subducted (pushed under/sinks)

3. As it sinks it can snag and get stuck. Pressure builds up as the plate tries to sink downwards

4. Eventually this pressure is released 5. This causes a jerking movement which is the

earthquake

There are two different types of crust/plates. Oceanic crust is more dense but thinner. It can sink. It is younger. Continental crust is thicker but less dense. As a result, it almost floats on top of magma. It does not sink and is younger.

How do volcanoes occur at constructive plate boundaries? 1. Two plates move away from each other driven by convection currents in the mantle 2. As they part a gap forms between the plates 3. Magma rises up through this gap, cools and solidifies to form a volcano.

How do earthquakes occur at constructive plate boundaries? 1. Two plates move away from each other driven by convection currents in the mantle 2. As they part a gap forms between the plates 3. Magma rises up through this gap. These actions cause the ground to shake causing very weak

earthquakes.

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Conservative plate boundaries/margins Only earthquake – no volcanoes form here

What is the difference between the primary and secondary effects of an earthquake? • Primary effects occur as or just after the earthquake has happened. They are a direct result of the

ground shaking (buildings collapsing, roads collapsing, death, injuries) • Secondary effects occur as a result of the primary effects (homelessness, damaged economy, fires

breaking out, landslides)

How do earthquakes occur? 1. Plates move in a similar, but not the same direction. At

different angles and speeds 2. As they move they can snag and get stuck on each other 3. Over time pressure will build up as the plates try to

move 4. Eventually this pressure will be released. This results in a

sudden jolting movement which is an earthquake.

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Earthquake in a LIC – Nepal Collision plate margin

The Nepal earthquake happened in April 2015. It measured 7.9 on the Richter scale. The earthquake happened 80km away from the capital city of Kathmandu however buildings were still destroyed here. Primary effects In total 9000 people died and 20,000 people were injured. Historical monuments and temples were destroyed. 4 out of 7 world heritage sites were badly damaged. 7000 schools were either badly damaged or destroyed. Secondary effects The ground shaking triggered devastating avalanches and landslides. In rural areas landslides wiped out entire villages as well as farm land causing food shortages. The avalanches on Mount Everest killed 19 people. The country’s economy was seriously affected by this earthquake as it damaged the valuable tourism industry. Children became very vulnerable. Their education was disrupted, many became malnourished. Human traffickers took advantage of orphans. The cost of the damage was $5 Billion. Immediate responses Residents ran out of buildings as the earthquake struck. Half a million tents were provided to shelter the homeless, many of these provided by charities like the Red Cross. The UK donated £70 million in assistance. Helicopters sprang into action to rescue climbers from Mount Everest. Long term responses Homes and schools had to be rebuilt. Landslides were cleared in the countryside. Walking routes on Mount Everest were repaired, this was open again in August in a bid to attract tourists that had been put off from the area. Charities like plan international set up cash for work programmes that had people repairing roads and clearing rubble.

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Earthquake in a HIC – L’Aquilla (Italy) Destructive plate margin The L’Aquila earthquake happened on the 6th of April 2009 measuring 6.3 on the Richter Scale. L’Aquila is located in central Italy. Primary effects In total 15,000 buildings collapsed including the San Salvatore Hospital and the University. 308 people died and 1500 were injured mainly as a result of building collapse. Secondary effects It is estimated that 60,000 people were made homeless as a result of the damage and destruction done to the older buildings. The economy of the city suffered, applications to universities declined as did the city’s population. The once bustling pubs and cafes of the city centre have struggled to remain open after a fall in business. A broken water pipe near the town of Paganica along with aftershocks caused a landslide which destroyed homes. $11.4 million worth of damage was caused. Immediate responses Within an hour the Italian Red Cross were searching for survivors. The city was declared in a state of emergency meaning that the EU could release funds to help the operation of over $500 million. The 60,000 homeless were put into hotels or provided with tents. Long term responses The residents did not have to pay their mortgages or taxes in 2010 and university fees were lowered for 3 years to try to encourage students back. 632 houses were demolished by 2016. New out of town housing estates were built for 11,000 people whose homes could not be restored. In a nutshell Earthquakes in LICs often cause more deaths and destruction as houses are poorly built, access to clean water and food is restricted after a disaster and response times can be slower due to lack of training and poor infrastructure slowing rescue operations down. In HICs people are often more prepared and well educated on how to react in a situation. Clean up and rebuilding will be fast in a HIC, although a LIC will get more financial support in aid from the international community to help with the rebuilding efforts. It could be argued that the economic effects are more severe in HICs whereas the social effects are more severe in LICs

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How can monitoring, prediction, protection and planning reduce the risks from a tectonic hazard?

What is it? Overview How does this help to reduce the effects?

Monitoring + prediction

using instruments to measure changes Gas sample, tilt meter Seismometer

Before a volcano erupts there will be an increase in temperature just below the surface, more sulphur dioxide will be released, and magma might push upwards changing the shape of the ground. This can be measured with a tilt meter. Predicting earthquakes is less accurate as there are no visible signs. Scientists can predict where they might occur but not exactly when. Small tremors might be a sign that a major earthquake is to follow. No major earthquakes have ever been accurately predicted.

Monitoring changes helps to predict when an eruption will take place. People can be evacuated. Number of deaths are reduced.

Protection Buildings and structures are built to be able to withstand the shaking of an earthquake

Earthquake proof buildings can be built with rubber shock absorbers at the base to minimise shaking and absorb the energy from the quake. They can also be built out of more flexible materials so that they can sway with the movement of the earthquake, this makes them less likely to collapse. Automatic switches can turn off gas supplies to buildings to reduce the risk of fires. In San Francisco soft storey houses (houses with a garage beneath) and retro fitted. This means they are strengthened so that the house does not collapse down into the garage.

By preventing buildings from collapsing lives will be saved, as most people die as a result of being crushed or trapped. There will also be less injuries. Reducing the risk of collapse also minimises the impact on the economy as buildings will not need to be rebuilt. Money is saved in the long run. Cities will still be able to function and trade as offices are intact.

Planning Getting ready, being prepared. Knowing how to respond.

In Japan children in school practice earthquake drills where an alarm will sound and they will rush under the tables. In cities people will be aware of evacuation routes out of their offices that lead them to an open space within the city People in areas prone to earthquakes are taught to practice drop, cover and hold. Emergency services practice responding to disasters to make this more efficient on the day

Reduces the risk from injury and death as people have planned and know how to react. Planning by emergency services such as the fire department and medical teams means that more lives can be saved.

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