Geography

Question 1

What is plate tectonics theory?

Answer 1

The generally accepted scientific theory that the earth’s lithosphere is broken up into a number of large tectonic plates which are moving very slowly. It builds on the concept of continental drift, developed by Alfred Wegener in 1912.

Question 2

What is the name of the supercontinent which has separated to form the world we know today?

Answer 2

Pangaea.

Question 3

What evidence exists for plate tectonics theory?

Answer 3

One piece of evidence is that some continents appear to fit neatly into one another e.g. the east coast of South America and the west coast of Africa. Another is seafloor spreading. As plates move apart at mid-ocean ridges new crust is formed. It magnetises in the direction of the Earth’s magnetic field, and the Earth’s magnetic field changes over time. This means there is an alternating pattern as new crust is created.

Question 4

Name the four layers of the Earth.

Answer 4

Inn`er core, outer core, mantle, crust.

Question 5

What are the two types of crust?

Answer 5

Oceanic crust (which is thinner but more dense) and continental crust (which is thicker but less dense).

Question 6

Why do tectonic plates move?

Answer 6

Convection currents cause tectonic plates to move (and gravitational pull may also play a part).

Question 7

What is a plate margin?

Answer 7

A plate margin is the point at which two plates meet. It can also be known as a plate boundary. Plate margins can be constructive, destructive and conservative.

Question 8

What happens at constructive plate margins?

Answer 8

At constructive plate margins plates move apart. As plates move apart cracks and fissures (lines of weakness) form, allowing magma to escape from the highly pressurised interior of the planet. It eventually erupts on to the surface and cools as new land (crust is created). This leads to the formation of volcanoes. The movement of magma through the crust causes stress build-up and subsequently earthquakes.

Question 9

What happens at destructive plate margins?

Answer 9

At destructive plate margins plates move towards each other. If an oceanic and continental plate meet, the denser oceanic plate subducts (sinks beneath) the less dense continental plate. This creates a deep ocean trench. As the oceanic crust descends, friction and increasing pressure and heat from the mantle melt the plate. Some of this molten material can work its way up through the continental crust through fissures and cracks in the crust. It collects in magma chambers and eventually leads to volcanic eruptions. 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. Due to this friction, pressure builds up and when one plate eventually slips past the other, seismic energy is released and an earthquake occurs.

Question 10

What happens at conservative plate margins?

Answer 10

At conservative plate margins, plate are moving past each other. They can move past in opposing directions, or in the same direction if they are moving at different rates / speeds. As they move past each other, 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. These shock waves are known as earthquakes.

Question 11

At which plate margins do earthquakes form?

Answer 11

Constructive, destructive and conservative.

Question 12

At which plate margins do volcanoes form?

Answer 12

Constructive and destructive. They do not form at conservative plate margins as crust is not being created or destroyed.

Question 13

What is meant by the term ‘primary effect’?

Answer 13

Primary effect are effects that occur as a direct result of the natural event e.g. buildings collapsing.

Question 14

What is meant by the term ‘secondary effect’?

Answer 14

Secondary effects are effects that occur as a result of the primary effects e.g. fires starting due to broken gas mains.

Question 15

List some primary effects that could occur as a result of a tectonic hazard.

Answer 15

Collapsing buildings; death or injury caused by caused by collapsing buildings; cracked and twisted roads.

Question 16

List some secondary effects that could occur as a result of a tectonic hazard.

Answer 16

Fires starting due to broken gas mains; businesses losing money or being forced to close; reduction in tourist numbers in an area; disease and famine due to a lack of clean water.

Question 17

What is meant by the term ‘immediate response’?

Answer 17

Immediate responses refer to how people react directly after a disaster (usually minutes to days after a disaster). For instance, temporary camps may be set up for people who have lost their homes.

Question 18

What is meant by the term ‘long-term response’?

Answer 18

Long-term responses are later reactions that happen in the months and years following a disaster. For instance, aid may be provided to rebuild homes which have been destroyed.

Question 19

What are your named examples to show how the effects and responses to a tectonic hazard vary between two areas of contrasting levels of wealth?

Answer 19

Haiti earthquake (2010); Christchurch earthquake (2011).

Question 20

List some primary effects of the Haiti earthquake (2010).

Answer 20

220,000 deaths and 300,000 injuries; eight hospitals or health centres in Port-au-Prince collapsed or were badly damaged; 100,000 homes and 30,000 commercial buildings destroyed.

Question 21

List some secondary effects of the Haiti earthquake (2010).

Answer 21

Fires caused by broken gas mains / electrical fires; tourist number reduced, leading to a loss of jobs in tourist industries.

Question 22

List some immediate responses to the Haiti earthquake (2010).

Answer 22

Emergency rescue teams arrived from other countries e.g. Iceland; neighbouring Dominican Republic provided emergency water and medical supplies as well as heavy machinery to help with search and rescue underneath the rubble.

Question 23

List some long-term responses to the Haiti earthquake (2010).

Answer 23

The EU gave $330 million and the World Bank waived the countries debt repayments for 5 years; the number of people still in relief camps 6 months after the earthquake was 1.6 million.

Question 24

List some primary effects of the Christchurch earthquake (2011).

Answer 24

181 deaths and 2000 injuries; the city’s cathedral spire collapsed.

Question 25

List some secondary effects of the Christchurch earthquake (2011).

Answer 25

Schools in Christchurch were closed for two weeks; Christchurch could not hold the five rugby world cup matches it had initially been scheduled to hold.

Question 26

List some immediate responses to the Christchurch earthquake (2011).

Answer 26

Temporary chemical toilets were provided for 30,000 residents; pop-up hospitals were set-up.

Question 27

List some long-term responses to the Christchurch earthquake (2011).

Answer 27

Earthquake drills implemented across the country; Canterbury Earthquake Recovery Authority was created to organise the rebuild of the region.

Question 28

Why do people continue to live in areas at risk from tectonic hazards?

Answer 28

One reason is that the soil surrounding volcanoes tends to be very fertile due to lava and ash deposits. This makes the land very economically productive for farmers. Another reason is that in less wealthy areas, some people cannot afford to move. A third reason is that tourism can be very popular (particularly by volcanoes) meaning people can earn money by operating small businesses in the area (e.g. selling souvenirs). A final reason is that in wealthier areas precautions have often been taken to greatly reduce risk (e.g. the building of earthquake-resistant buildings).

Question 29

What are the four main management strategies for reducing the risks from a tectonic hazard?

Answer 29

Monitoring, prediction, protection and planning.

Question 30

In the context of tectonic hazards, explain what is meant by monitoring.

Answer 30

Monitoring involves the use of scientific equipment to detect warning signs of events such as volcanic eruptions. Examples include remote sensing to detect heat and changes to the volcano's shape and instruments to detect gases as magma rises. Earthquakes are much more difficult to monitor and often happen with little or no warning.

Question 31

In the context of tectonic hazards, explain what is meant by prediction.

Answer 31

Using historical evidence and monitoring, scientists can make predictions about when and where a tectonic hazard may happen.

Question 32

In the context of tectonic hazards, explain what is meant by protection.

Answer 32

In the case of earthquakes, protection is the most effective way to reduce risk. This is often done by constructing earthquake-resistant buildings which cope with the ground shaking associated with earthquakes. The sheer power of a volcanic eruption makes it difficult to protect people and property but embankments can be built to divert lava away from buildings.

Question 33

In the context of tectonic hazards, explain what is meant by planning.

Answer 33

Hazard maps can be produced to show areas that would likely be affected by a volcanic eruption. Land use can then be restricted (e.g. not building housing in these areas) and evacuation plans developed. Evacuation plans are also useful with regards to earthquakes, as are earthquake drills and the preparation of survival kits.

Question 34

What is a natural hazard?

Answer 34

A natural hazard is a natural event which threatens people and property. Examples include earthquakes, volcanoes and tropical storms.

Question 35

Why are natural events not always classified as natural hazards?

Answer 35

Not all natural events threaten people and property. For example, an earthquake could occur in an area where nobody lives.

Question 36

What are the different types of natural hazard?

Answer 36

Tectonic hazards (e.g. earthquakes, volcanoes, tsunamis) and weather hazards (e.g. tropical storms).

Question 37

List some key factors affecting hazard risk.

Answer 37

The level of economic development of the affected area; the magnitude / severity of the natural event; the level of urbanisation of the affected area; the level of education of the affected area; the size of the population of the affected area.

Question 38

Explain how the level of economic development of an area could affect hazard risk.

Answer 38

If an area has a high level of development then we can assume that the quality of its buildings will be higher than an area with a low level of development. This means the buildings would be better able to e.g. withstand an earthquake. Similarly, more economically developed areas tend to have higher education levels, meaning that people are likely to be better prepared in the event of a natural hazard e.g. understanding that a tsunami could be imminent if the tide recedes. They would be more likely to evacuate the area, reducing hazard risk.