Natural Hazards

Question 1

What are the four types of natural hazards?

Answer 1

Geological/tectonic, climatic, geomorphological, biological

Question 2

Name an example of a natural hazard from each of the four categories

Answer 2

Geological: earthquakes, tsunamis, volcanic eruptions
Climatic: tornadoes, floods, droughts
Geomorphological: Avalanches, landslides (mass movement)
Biological: infectious diseases

Question 3

What is a natural hazard?

Answer 3

A physical process or event which has the potential to cause loss of life and damage to property

Question 4

What is an earthquake?

Answer 4

A violent shaking of the Earth’s crust, caused by a snap somewhere in the Earth’s crust. The shaking may be up and down or side to side

Question 5

What is the focus of an earthquake?

Answer 5

The point where the snap takes place in an earthquake

Question 6

What is the epicentre of an earthquake?

Answer 6

Directly above the focus of the earthquake on the surface

Question 7

What are seismic waves?

Answer 7

Waves of energy released from the focus, sent out in all directions like ripples

Question 8

What is a volcano?

Answer 8

A crack or a fissure in the Earth’s crust which may occasionally erupt out ash, molten rock and gas from underground to the Earth’s surface

Question 9

What are the main differences between composite and shield volcanoes?

Answer 9

Composite volcanoes have a conical shape, whereas shield volcanoes have gentle, undulating sides, without a clear shape and with many different peaks.
Composite volcanoes rarely erupt, but when they do the eruption is violent and very destructive, while a shield volcano erupts more frequently with less force.

Question 10

Why are shield and composite volcanoes different?

Answer 10

In a shield volcano, magma does not contain much silica and is very hot and runny, so it has a low viscosity. It does not require much force to bring it to the surface, so eruptions are weaker and more frequent. It takes a long time to cool once above ground, so shield volcanoes have a large surface area, and vice versa with composite volcanoes. Shield volcanoes form on constructive plate margins and composite volcanoes form on destructive plate margins.

Question 11

What is a constructive plate margin?

Answer 11

Where two plates are moving away from each other, so magma rises and cools in the gap and forms new rock

Question 12

What is a destructive plate margin?

Answer 12

Where oceanic crust and continental move towards each other and the oceanic crust subducts under the continental crust

Question 13

What is a collision margin?

Answer 13

Where two continental plates move towards each other and rocks in between are forced upwards, creating fold mountains

Question 14

What is a conservative plate margin?

Answer 14

Where two plates are sliding past each other, either in different directions or in the same direction at different speeds

Question 15

What is the composition of the Earth?

Answer 15

A solid inner core at the centre, a liquid outer core surrounding it, a semi-liquid mantle surrounding that and a crust floating on the mantle

Question 16

Why do the tectonic plates move?

Answer 16

Due to convection currents in the mantle

Question 17

Why do earthquakes happen?

Answer 17

Tectonic plates floating on the mantle move due to convection currents in the mantle. The plate margins are jagged, so plates lock, pressure builds up, and the plate margin suddenly snaps as the plates lurch past each other, and seismic waves are released in an earthquake

Question 18

What are benefits of living close to volcanoes?

Answer 18

Fertile soil - e.g. nitrates, allowing for agriculture
Geothermal energy - in Iceland 1/4 of electricity comes from geothermal energy
Attracting tourists and visitors

Question 19

What are hazards of living close to volcanoes?

Answer 19

Lava flows
Ash clouds
Pyroclastic flow
Lahars

Question 20

What are the four ways of volcano management strategies?

Answer 20

Monitoring
Predicting
Protection
Planning

Question 21

What are immediate/primary hazards caused by earthquakes?

Answer 21

Fires - from ruptured gas pipes and electricity cables
Traffic/rail accidents - from shaking and broken roads and tracks
Collapsing buildings - people can be crushed underneath them
Mass movements - e.g. landslides, mudslides and avalanches in sloped areas

Question 22

What are long term/secondary hazards caused by earthquakes?

Answer 22

Homelessness - people can die from exposure or hypothermia
Lack of clean water - infectious diseases can spread e.g. cholera
Shortages of emergency aid

Question 23

What are the Richter and Mercalli scales?

Answer 23

Ways of measuring earthquakes. The Richter scale measures the amount of energy released at the focus of the earthquake and is logarithmic, so the next number is 10x more powerful than the last. The Mercalli scale is based purely off observation and ends at 12, with complete destruction of buildings and twisting of the ground.

Question 24

What are the three Ps of reducing earthquake impact?

Answer 24

Prediction, protection and preparation

Question 25

What are lava flows?

Answer 25

Lave erupted from the mantle during an eruption that destroys buildings, starts fire, and destroys farmland. They move slowly, so people can usually be evacuated safely.

Question 26

What are ash clouds?

Answer 26

Clouds of ash such as sulphur dioxide let out when a volcano erupts. They can kill people by asphyxiation and cause properties to collapse, and block out the Sun, causing medium term climate change. This kills crops, causing food shortages.

Question 27

What are pyroclastic flows?

Answer 27

Very fast moving - over 200km/h - flows of hot ash, rock and gas. They have temperatures between 200 and 700 degrees. Anything in their path is destroyed and they are very difficult to escape from if no warning is given.

Question 28

What are lahars?

Answer 28

A type of mudflow made from water mixed with volcanic ash and rock. The water often comes from snow and ice on the cap of the volcano that melts in an eruption. They can cause drowning, destroy property, destroy farmland, leave people stranded, and contaminate the water supply.

Question 29

What is monitoring and predicting in terms of volcanoes?

Answer 29

Constantly checking signs of a volcano’s activity in order to detect warning signs of an imminent volcano eruption e.g. using tiltmeters and gas measurers

Question 30

What is protection in terms of volcanoes?

Answer 30

Building structures to withstand volcanic eruptions e.g. earth embankments and explosives to divert lava flows and lahars away from property

Question 31

What is planning in terms of volcanoes?

Answer 31

Looking at how previous eruptions happened and building in areas that have not been affected by eruptions

Question 32

What is prediction in terms of earthquakes?

Answer 32

Forecasting when and where an earthquake will happen e.g. in Japan fault lines are monitored and a warning is set out when a movement occurs, as this is usually about a minute before and earthquake, giving people some time to prepare (e.g. going under a table)

Question 33

What is protection in terms of earthquakes?

Answer 33

Building structures that can withstand an earthquake e.g. using deep foundations, flexible materials, tuned mass dampers, and automatic window shutters to prevent falling glass

Question 34

What is preparation in terms of earthquakes?

Answer 34

Practising what to do when an earthquake happens in drills at school, workplaces, and emergency centres

Question 35

What were the primary effects of the 2010 Haiti Earthquake?

Answer 35

220,000 people died; 250,000 were seriously injured
1/3 of all buildings in Port-au-Prince were completely destroyed (~300,000)
Roads and transport systems were severely damaged, as well as already poor electricity, water, and waste systems.

Question 36

What were the secondary effects of the 2010 Haiti Earthquake?

Answer 36

Lack of water and food
Homelessness - 1,300,000 people were left on the streets, 13% of the population
Cholera outbreak - 600,000 cases, 8,000 deaths, and a cost of $2bn to stop the outbreak
Poverty - 30,000 businesses were destroyed and the %age of people living below the poverty line rose from 50% to 80%

Question 37

What were the primary responses to the earthquake in Haiti?

Answer 37

Rescuing people trapped and injured - using Haitian emergency services and international rescue teams flown in
Giving out food, clean water, hygiene packs and water purification kits
Constructing toilets
NGOs like Oxfam putting up emergency shelters to temporarily house 1,000,000 people

Question 38

What problems did NGOs face when trying to provide aid to Haiti?

Answer 38

Lack of transport options - roads were generally poor quality and many had been destroyed
People mobbing and taking supplies from trucks delivering food
Poor quality sewage system that was completely destroyed by the earthquake, leading to the spread of disease

Question 39

How has Haiti attempted to reduce the impacts of a future earthquake?

Answer 39

Running practice drills with the emergency population and emergency services
Making improvements to building - building from thin and light materials and using foundations
Using intermediate technology e.g. pumps and wells to provide clean water to villages

Question 40

What were the magnitudes of the 2010 Haiti and 2011 Christchurch earthquakes?

Answer 40

Haiti - 7

Christchurch - 6.2

Question 41

What were the primary effects of the 2011 Christchurch Earthquake?

Answer 41

185 people killed and ~2,000 people injured
Hundreds of kilometres of water and sewage pipes damaged
50% or more of Central City buildings severely damaged including the cathedral, which lost its spire
Liquefaction damaged roads and buildings
80% of the city without electricity

Question 42

What were the secondary effects of the 2011 Christchurch Earthquake?

Answer 42

Businesses closed for long period, causing unemployment
Schools having to share classrooms
Difficult to travel as roads were damaged
Christchurch could no longer host the Rugby World Cup so lost the benefits of it e.g. tourism
Demolishing and rebuilding the CBD cost $25bn to the NZ economy

Question 43

What were the primary responses to the Christchurch earthquake?

Answer 43

Emergency services rescuing trapped and injured people. They were well trained with specialist equipment
Temporary accommodation e.g. caravans, motorhomes, and B&Bs made available to people made homeless by the earthquake
Injured treated at hospitals

Question 44

What were the secondary responses of the 2011 Christchurch Earthquake?

Answer 44

National earthquake drill day is held every year, where the whole country takes part in a drill
New buildings must follow strict codes such as being flexible to be more earthquake proof

Question 45

Why were the impacts of the Haiti earthquake so much greater than the Christchurch earthquake?

Answer 45

New Zealand had specialist teams and aid on call for an earthquake, while Haiti could not afford this
In Haiti there were 0.25 doctors per 1000 people, while in New Zealand there were 2.4
Haiti lacked a stable government and most work was done by NGOs