Geography Paper 1 Section A - Tectonic Hazards

Question 1

How does the movement of magma cause convection currents that move tectonic plates?

Answer 1

1. The core heats the magma in the mantle
2. The hot, heated magma is less dense than its surroundings, so it rises upwards
3. When it reaches the top, it cools
4. The magma becomes more dense and therefore sinks back down to the bottom
5. It is heated up again, and the cycle continues
6. The plates, which lie on top, are pushed and pulled by the convection currents in the magma

Question 2

How do tectonic hazards occur at constructive plate margins?

Answer 2

At constructive plate margins, plates are moving away from each other:

1. As plates move apart, cracks and fissures are formed, allowing magma to escape between the gaps left by the plates
2. It eventually erupts onto the surface as lava and cools as new land(where the crust is created)
3. This leads to the formation of volcanoes - where eruptions are often runny and free-flowing creating flatter volcanoes
4. The movement of magma through the crust causes rocks in the crust to crack and fracture, triggering earthquakes

Question 3

How do tectonic hazards occur at destructive plate margins?

Answer 3

At destructive plate margins plates move towards each other.

1. If an oceanic and continental plate meet, the denser oceanic plate subducts (sinks beneath) the less dense continental plate
2. This creates a deep ocean trench. As the oceanic crust descends, friction and increasing pressure and heat from the mantle melt the plate.
3. Some of this molten material can work its way up through the continental crust through fissures and cracks in the crust.
4. It collects in magma chambers and eventually leads to volcanic eruptions.
5. The magma is viscous meaning it tends to produce composite volcanoes which are typically tall and conical in shape.
6. The movement of the plates grinding past one another can create earthquakes. As the denser oceanic plate subducts, the plates can get ‘stuck’ as they move against one another.
7. Due to this friction, pressure builds up and when one plate eventually slips past the other, seismic energy is released and an earthquake occurs.
8. Earthquakes are also triggered when the magma rises up through the crust, causing it to crack and fracture.

Where two continental plates meet there is no subduction. Instead, the two low-density plates collide, crumpling and uplifting the crust, forming fold mountains and triggering powerful earthquakes. There are no volcanoes at collision margins because there is no magma.

Question 4

How do tectonic hazards occur at conservative plate margins?

Answer 4

At conservative plate margins, plates are moving past each other.

1. The parallel plates can move past in opposing directions, or the same direction if they are moving at different speeds
2. When these plates move side by side, friction builds up
3. Stress energy builds as the plates grind against one another. When this stress energy is eventually released as plates slip and shift, shock waves are sent through the Earth’s crust
4. These shock waves are known as earthquakes.

There is no volcanic activity because there is no magma.

Question 5

Why do people live in hazardous areas? - education.

Answer 5

-A lack of education & and information may mean that people will not take the issue seriously and are not aware of the risks

Question 6

Why do people live in hazardous areas? - poverty.

Answer 6

-Some families are poor so they cannot afford to move away Farmers depend on fertile land provided by volcanoes

Question 7

Why do people live in hazardous areas? - high population density.

Answer 7

-Another factor is areas of high population density, e.g. Tokyo. It would take a lot of time & and money to move a large amount of people away therefore they adapt to these conditions.

Question 8

Why do people live in hazardous areas? - monitoring and management.

Answer 8

-Major advances in monitoring technology which have led to warning systems to be developed. Many people choose to live here as they know the risk will be reduced by the warning systems.

-Developments in better building design, for example in Japan, many buildings have been built to withstand earthquakes by using carbon fibre ‘curtain’ to minimise the effect of shaking

Question 9

How can we monitor tectonic hazards?

Answer 9

-Active volcanoes are monitored using a range of equipment:

Seismometers: These record earth movements and can detect the slightest tremor

-Lasers and tiltmeters: Used to detect ground deformation, changes in land shape can be a sign of rising magma

-Remote sensing: Satellites are used to detect heat increases within the volcano another sign of rising magma

-Gas sensors: These detect increases in gases such as sulphur and radon which increase before an eruption

-Earthquakes: seismometers: These record earth movements and can be used to detect foreshocks

-Gas sensors: Detect increases in radon gas which some scientists believe is released prior to an earthquake

-Ground water levels: Changes in groundwater levels have been recorded before earthquakes

Question 10

How can we protect ourselves from a tectonic hazard?

Answer 10

-Volcanoes: Evacuation and exclusion zones move people out of areas at risk

-Buildings cannot be protected against lava or pyroclastic flow

Strengthening of roofs to support the weight of falling ash

-Earthquakes: many countries now practice earthquake drills - ‘drop, cover and hold on’ ensuring people know how to best protect themselves in an earthquake

-Earthquake resistant building design - such as shutters on windows and reinforced steel cross braces

-Sea walls to protect against tsunami

Question 11

How can we predict tectonic hazards?

Answer 11

Volcanoes:

-Monitoring of volcanoes now allows more accurate predictions of eruptions to be made

-This allows for evacuation and exclusion areas to be put in place

-Accurate timings for eruptions are not possible

Earthquakes:

-Impossible to predict the date, time or location

Question 12

How can we plan for a tectonic hazard?

Answer 12

Volcanoes and earthquakes:

-Hazard mapping and risk assessment are used to identify areas which are at greater risk - this means people can be moved or buildings restricted in those areas, particularly essential buildings (hospitals) and transport

-Evacuation plans

-Education about what actions to take, including drills

-Stockpile of emergency supplies

-Training of emergency services

Question 13

Identify the secondary effects of the Santiago, Chile earthquake in 2010?

Answer 13

-Landslides triggered by the earthquake damaged 1500km of roads. Debris blocked roads for weeks which cut off rural communities

-Tsunami was triggered by an earthquake which devastated coastal towns and destroyed ports.

-Fires broke out in buildings due to burst pipes and other complications. Fire in a chemical plant near Santiago meant many people had to be evacuated

Question 14

Identify the primary effects of the Santiago, Chile earthquake in 2010?

Answer 14

-500 killed and 12000 injured

-800,000 people affected overall

-22000 homes destroyed, 4500 schools, 53 ports and 56 hospitals

-Santiago airport was badly damaged

-Water, electricity and communications lost in many places

-Cost of USD$30 billion

Question 15

Identify the primary effects of the Kathmandu, Nepal earthquake in 2015?

Answer 15

-9000 killed and 20000 injured

-8 million people affected(1/3 of Nepal’s population)

-3,000,000 left homeless

-7000 schools were destroyed and 50% of all shops destroyed(food and supply shortages)

-Power, water and communications severely affected

-1.4 million people were urgently in need of food, water and shelter

-Historical landmarks damages

-Cost of USD $5 billion

Question 16

Identify the secondary effects of the Kathmandu, Nepal earthquake in 2015?

Answer 16

-Landslides and avalanches triggered by ground shaking, causing widespread damage to infrastructure, blocking roads and trapping people under snow and rubble

-Avalanches on Mount Everest killed 19 and left hundreds missing

-Landslides blocked rivers such as the Kali Gandaki River and many evacuated in case of flooding

Question 17

Identify immediate responses of the Kathmandu, Nepal earthquake in 2015?

Answer 17

-International aid arrived from the UK, India and China. Brought search and rescue teams, medical support and supplies. Over £87 million was raised in aid by donations

-Helicopters used for search, rescue and supply distribution. Those left stranded were rescued by helicopters and communities cut off by landslides were given vital supplies

-Half a million tents were provided after the earthquake, many from UNICEF. These provided shelter for the homeless and were used as temporary classrooms and healthcare facilities as aftershocks of earthquakes prevented people from using buildings.

-300000 fled from the capital, Kathmandu, to seek shelter elsewhere

-Field services were set up as hospitals were overcrowded with casualties.

-Social media was used as a means of communication for those affected. Facebook introduced a safety check feature after the earthquake which allowed people to mark themselves as ‘safe’ to family and friends.

Question 18

Identify immediate responses of the Santiago, Chile earthquake in 2010?

Answer 18

-Emergency services were deployed quickly. Search and rescue teams were sent out to search and help survivors, and emergency field hospitals were set up to help the injured.

-Within 24 hours, temporary repairs were made to the Route 5 north-south highway. This reconnected the capital to other areas and allowed response teams to travel to more remote communities.

-Temporary shelters were set up for the homeless. The Chilean government immediately distributed 5,000 temporary shelters and a further 30000 temporary emergency shelters were built after fundraising

-International aid groups set up emergency response units for healthcare and emergency supply distribution

-Power and water restored to 90% of homes within 10 days

-USD 60 million was raised in relief funds after a national appeal which went towards reconstruction and emergency aid

Question 19

Identify long-term responses of the Santiago, Chile earthquake in 2010?

Answer 19

-Chile set up a national housing reconstruction plan one month after the earthquake, pledging USD $2.5 billion in housing subsidies for 196,000 households affected

-Thousands of houses and buildings were deemed unsafe to stay standing, and had to be demolished

-Foreign aid was not heavily relied upon as Chile had the funds available for reconstruction and recovery. The frequency of earthquakes in Chile meant the country was prepared for the disaster

-The president of Chile announced that full recovery could take 4 years, especially to fully reconstruct builidings and ports

Question 20

Identify long-term responses of the Kathmandu, Nepal earthquake in 2015?

Answer 20

-In 2019, 3/4 of homes that were destroyed by the earthquake were either fully rebuilt or under repair. Over 7000 schools were also rebuilt

-The government introduced sticker building codes with better earthquake resistance

-Landslides were cleared and roads were repaired. Temporary lakes formed by landslides that blocked rivers had to be carefully drained, such as in the Kali Gandaki River

-In June 2015, Nepal hosted an international conference to seek advice and financial support from other countries

-By August 2015, repairs to Everest base camp and mountain routes meant the area could be reopened to mountaineers. Other tourist sites were opened over time

-In September 2015, Nepal suffered severe shortages of fuel, medicines and earthquake relief materials after India imposed a blockade at the Nepal-India border, stopping goods from entering Nepal