Hazardous Environments (Including Case Studies)

Question 1

Explain the terms natural ‘hazard’ and natural ‘disaster’. What is the difference?

Answer 1

• Natural Hazard - A natural event (for example earthquake, flood, landslide, volcanic eruption) that threatens or causes damage, destruction and death.
• Natural Disaster - The results of a natural hazard taking place, such as deaths, injuries and destruction of property.

Difference :

• Hazards are related to a future occurrence and disasters to past or current occurrences.
• A hazard event becomes a disaster once significant damage and/or loss of life has been caused.

Question 2

Explain why some places are more hazardous than others.

Answer 2

• Some places experience more than one type of natural hazard event.
• Some places experience natural hazards more frequently than others.
• In some places the hazards are stronger and more destructive than in others.
• Some places are better able to cope with the damaging impacts of natural hazards.

Question 3

How can hazards be classified into four categories?

Answer 3

Geological :
- Earthquakes
- Volcanic Eruptions
- Landslides

Climatic :
- Storms
- Floods
- Droughts

Biological :
- Fires
- Pests
- Diseases

Technological :
- Nuclear Explosion
- Transport Accidents
- Pollution

Question 4

Describe the distribution of Earthquakes and Volcanoes.

Answer 4

• Both earthquakes and volcanoes occur along tectonic plate boundaries.
• Volcanoes occur largely along the “ring of fire” near the coast where oceanic and continental crust meet forming a destructive plate boundary. There is a cluster near Asia.

Question 5

Describe the distribution of Tropical Cyclones.

Answer 5

Occur in warm, tropical oceans near/at the coast.

Question 6

Explain the term ‘tectonic plate’.

Answer 6

A rigid segment of the Earth’s crust which can ‘float’ across the heavier, semi-molten rock below. Continental plates are less dense, but thicker than oceanic plates. Movement occurs.

Question 7

Explain the difference between Continental and Oceanic crust.

Answer 7

Continental Crust (land) :
- Is 30-35 km, thick and less dense made mostly of granite thus ‘floats’.

Oceanic Crust (under oceans) :
- Is 6-8 km, thin but dense as it is made mostly of basalt thus causing it to sink.

Question 8

What are ‘Convection Currents’?

Answer 8

Occur within the molten rock in the mantle, act like a conveyor belt moving the tectonic plates above.
Hot rock in the mantle rises heated by the earth’s core and then move outwards and cool as they are replaced by cooler particles thus moving and dragging the earth’s tectonic plates apart/towards each other.
https://www.youtube.com/watch?v=ryrXAGY1dmE

Question 9

Describe and explain what is meant by a ‘constructive’ plate boundary. Give examples…

Answer 9

Constructive…
- Where two plates move away from each other (usually under the sea) due to convection currents and friction. Magma rises upwards from the mantle of the earth in a volcanic eruption but with not as much force compared to a destructive plate boundary to fill the gap which cools forming new land features such as underwater volcanoes and submarine mountains.
- An example of this type of boundary is the Mid-Atlantic Ridge.

Question 10

Describe and explain what is meant by a ‘destructive’ plate boundary. Give examples…

Answer 10

Destructive…
- Where two plates (one continental and one oceanic) move into each other due to convection currents and friction but then the oceanic plate becomes sub-ducted under the continental plate because it is more dense. As the rock from the oceanic plate goes into the mantle of the earth it melts and pushes the magma into the chambers of a volcano or gaps in the continental plate and thus erupts due to the build up of pressure.
- Earthquakes also occur here due to the friction between the oceanic and continental plates during the process of subduction violently shaking the two crusts.
- An ocean trench is formed between the gap where the oceanic crust descended into the mantle under the continental crust.
- An example of a destructive plate boundary is when the Nazca plate is forced under the South American plate.

Question 11

Describe and explain what is meant by a ‘collision’ plate boundary. Give examples…

Answer 11

Collision…
- Where two plate boundaries (both continental or both oceanic) being of similar densities move towards each other due to convection currents and friction they collide and fold together forming a series of fold mountain ranges pushing upwards as well as a little bit downwards forming a deep section of crust. Earthquakes occur here due to the friction.
- An example of a collision plate boundary is the Himalayas; formed by the Indo-Australian plate collided with the Eurasian plate.

Question 12

Describe and explain what is meant by a ‘conservative’ plate boundary.

Answer 12

Conservative…
- Where two plate boundaries rub and slide against each other as they move in opposite directions or in the same direction at different speeds thus resulting in Earthquakes as a result of a build up of kinetic energy is released because the movement of the plates overcomes the force of friction and jolts violently.
- The focus/epicentre of the earthquake is formed at a point of friction and seismic waves are released and the strength decreases the further away you go.

Question 13

Explain what is meant by a ‘composite’ volcano. What are some of the characteristics?

Answer 13

• Composite Volcano - Steep-sided volcano formed by a sequence of explosive eruptions. - Can be highly explosive and dangerous.
• Found on destructive plate boundaries.
• Also known as stratovolcanoes.

Characteristics…
Acidic lava, which is very viscous (sticky).
Steep sides as the lava doesn’t flow very far before it solidifies.
Alternate layers of ash and lava. For this reason, they’re also known as stratovolcanoes. Strato means layers.
Violent eruptions.
Longer periods between eruptions.

Question 14

Explain what is meant by a ‘shield’ volcano. What are some of the characteristics?

Answer 14

A gently sloped (shield-shaped) volcano, formed by the cooling of low viscosity (‘runny’) lava.
- Gentle eruptions and typically not dangerous.
- Found at constructive plate boundaries and hot spots.

Characteristics…
Basic lava, which is non-acidic and very runny.
Gently sloping sides as the lava flows for long distances before it solidifies.
No layers, as the volcano just consists of solidified lava.
Less violent eruptions.
Shorter periods between eruptions.

Question 15

What and where is the ‘ring of fire’

Answer 15

The majority of active volcanoes are located along the Pacific Rim in what is known as the Ring of Fire.
This is due to plate tectonics.
Because the massive Pacific Plate is made of heavier, more dense, oceanic crust, it pushes under the surrounding lighter continental crust forming DESTRUCTIVE PLATE BOUNDARIES.

Question 16

What are the main features of a volcano?

Answer 16

• Crater - The depression at the top of the vent.
• Magma chamber - The source of the molten rock.
• Volcanic bombs, ash and gases - Airborne materials emitted from the volcano.
• Main vent - The pipe up the middle of the volcano
• Secondary (parasitic) cone - A secondary cone forming on the side of a volcano

Question 17

What are ‘hot spots’?

Answer 17

A hot spot is a plume of magma that rises vertically through the mantle. The magma pushes through the crust forming shield volcanoes. The plume is stationary but the crust moves over the plume.

A hotspot is a particularly hot part of the mantle that causes rock to melt, producing magma.
This magma rises up through the crust and forms a volcano.
As the plate moves, the volcano is carried away from the hotspot and becomes inactive.
Thus therefore allowing a new volcano to be formed above the hotspot.
Over millions of years, a long chain of volcanoes can form.
An example of this is the Hawaiian islands

Question 18

Explain the hazard of ‘lava flows’.

Answer 18

Since few lava flows reach much beyond 10 km from the volcanic crater, they do not cause as much death and destruction as you might think.
Lava flows may destroy farmland, buildings and lines of transport, but lives are rarely lost.

Question 19

Explain the hazard of ‘ash’.

Answer 19

This may be thrown into the air during a violent eruption. Often ash is carried in the wind and therefore it can affect a large area. This happened over much of Europe in 2010 when a volcano in Iceland erupted. The ash cloud brought air travel to a halt. The further away from the volcano, the thinner the deposits of ash will be. Ash causes much damage by simply blanketing everything, from crops to roads. Roofs of buildings will collapse if the weight of the deposited ash is great. Air thick with ash can asphyxiate humans and animals.

Question 20

Explain the hazard of ‘gas emissions’.

Answer 20

Sulphur gases are not the only type emitted during an eruption. Other gases emitted, notably carbon dioxide and cyanide, can also kill. Being dense, they keep close to the ground. Particularly lethal are what are known as pyroclastic flows.

Question 21

Explain the hazard of ‘pyroclastic flows’.

Answer 21

A devastating eruption of extremely hot gas, ash and rocks; the downslope flow of this mixture is capable of reaching speeds of up to 200 kph.
Pyroclastic flows cause death and destruction as they damage agriculture, causing lowered food intake & famine. Sulphur clouds means no flights to escape eruptions = further damage due to congestion of roads as people are in a frenzy to save themselves and their families and be evacuated to safety.

Question 22

Explain the hazard of ‘lahars’.

Answer 22

Masses of rock, mud and water that travel quickly down the sides of a volcano.

Question 23

Explain the hazard of ‘tsunamis’.

Answer 23

A series of larger-than-normal waves, which are usually caused by underwater volcanic eruptions or underwater earthquakes.
The movement of the crust and erupted material displaces the water creating a tsunami towards the shore threatening major damage.

Question 24

How can we measure the intensity of volcanic eruptions?

Answer 24

The Volcanic Explosivity Index (VEI) is a measure of the explosiveness of volcanic eruptions.
It uses a logarithmic scale from 1 to 8, with each interval on the scale representing a tenfold increase in the volume of material emitted during the eruption.
A value of 0 is given for non-explosive eruptions, defined as less than 10,000 m3 of tephra (ash) ejected.
A value of 8 represents a mega-colossal explosive eruption, ejecting up to 1,000 km3 of tephra.

Question 25

Explain what is meant by ‘primary’ and ‘secondary’ impacts.

Answer 25

Primary Impacts - Caused directly by the products of a volcanic eruption or earthquake, e.g. lava flow, etc.
Secondary Impacts - The knock-on consequences/effects of the primary impacts , e.g. forest fire caused by lava flow, etc.

Question 26

Define the term ‘vulnerability’.

Answer 26

The potential of a human or animal society to be harmed, by a natural hazard event.

Question 27

Explain the primary impacts of a volcanic eruption.

Answer 27

• Erupted Lava Covers/Destroys Farmland, Homes, Businesses & Infrastructure.
• Pyroclastic Flows, Lahars, etc.
• Ash Clouds Cover Everything & Make Poor Visibility For Flight Paths.
• Water Contamination & Lung Irritation
• Vegetation and forests burned = loss of biodiversity.

Question 28

Explain the secondary impacts of a volcanic eruption,

Answer 28

• Rising sea levels due to climate change causing flooding.
• Destruction of homes, schools and businesses leads to a range of social and economic effects, including loss of education and unemployment.
• Psychological trauma is associates with the loss of family or friends.
• Global cooling due to ash clouds.
• Migration causes overpopulation.

Question 29

Explain the secondary impacts of a volcanic eruption,

Answer 29

• Rising sea levels due to climate change causing flooding.
• Destruction of homes, schools and businesses leads to a range of social and economic effects, including loss of education and unemployment = widespread poverty.
• Psychological trauma is associates with the loss of family or friends.
• Global cooling due to ash clouds.
• Migration causes overpopulation.
• Food Shortages.
• Land becomes un-usable for agriculture.
  Ash covers plants causing a lack of photosynthesis and crop failure.

Question 30

Why are some people more vulnerable to the impacts of volcanic eruptions that others?

Answer 30

• Location – Countries that experience a high frequency of hazard event. E.g. Indonesia and Japan are located on destructive plate boundaries, at higher risk of VEI 4+ eruptions. Settlements located on or near the slopes of active volcanoes are more vulnerable, e.g. Naples.
• Development – Countries that have higher levels of economic development and wealth are better able to prepare for and respond to natural hazards. Poorer countries have a lower capacity to cope.

Question 31

Describe the location of Mount Merapi in Indonesia.

Answer 31

• Located on the island of Java in Indonesia. It is North of the city of Yogyakarta. It is 2,910m high and has been erupting regularly since the 1500s.
• The volcano and its eruptions were caused by the Indo-Australian Plate being subducted beneath the Eurasian Plate.
• Pyroclastic flows are not uncommon, lahars also occur, and large amounts of ash.

Question 32

Describe the location of Mount Ontake.

Answer 32

• Located on the islands of Japan, part of the pacific ‘ring of fire’, the subduction zones around the Pacific rim that form volcanoes.
• The islands of Japan lie at the junction of three major plates, with the Pacific plate sub-ducting under the Philippine Plate and Eurasian Plate whilst the Philippine plate sub-ducts under the Eurasian Plate.
• It is the second highest mountain in Japan.

Question 33

Explain what is meant by a ‘phreatic eruption’,

Answer 33

A phreatic eruption is one caused by the heating of ground water/surface water by magma causing nearly instantaneous evaporation of water to steam resulting in an eruption of steam, water, gases, ash, rock and volcanic bombs. It usually produces sticky, acidic lava.

Question 34

What caused the Mount Ontake eruption?

Answer 34

• The Mount Ontake eruption was caused by the widespread cracking of previously intact rock by intensely boiling groundwater via magma in the mantle of the earth causing a phreatic eruption.

Question 35

Explain the impacts of the Mount Ontake eruption.

Answer 35

• Hikers and people living nearby were either killed or injured by toxic gases, pyroclastic flows, etc.

Question 36

Explain what is meant by an ‘earthquake’.

Answer 36

A sudden or violent movement within the Earth’s crust followed by a series of shocks.

Question 37

Explain what is meant by the ‘fault’, ‘focus’, ‘epicentre’ and ‘seismic waves’ of an earthquake.

Answer 37

• Fault - A fracture between two blocks of rock, where movement occurs when rock is under pressure.
• Focus - The point inside the Earth’s crust from which the pressure is released when an earthquake occurs. Also called hypocentre.
• Epicentre - The point on the Earth’s surface directly above the focus of an earthquake
• Seismic Waves - Energy released during earthquake. Also called shock waves.

Question 38

Describe & Explain the Global Distribution of Earthquakes.

Answer 38

• Earthquakes are dispersed on every continent (some are more prone to earthquakes than others) predominantly found near tectonic plate boundaries, usually offshore or near the coast, one anomaly of this is inland Russia.
• There is a large linear cluster located in East Asia, South and North America known as the Pacific “Ring of Fire” Where many destructive plate boundaries are found making it one of the most active places for volcanoes and earthquakes to occur.
• This is due to collisions/friction between tectonic plates as they move due to convection currents in the mantle causing sudden or violent movements within the Earth’s crust.

Question 39

At which plate boundary are earthquakes most powerful?

Answer 39

Destructive Plate Boundaries.

Question 40

Why do earthquakes occur near plate boundaries?

Answer 40

• Crustal plates do not glide smoothly past one another. Instead, tremendous friction exists along plate boundaries, keeping the plates firmly stuck together.
• The stress, or force, of plate motion builds strain in the rocks until friction is overcome and the rock that has been ‘stuck’ together suddenly breaks loose.
• This sudden movement occurs along plate boundaries or fault lines, where the rock is weaker.
• The release of energy that occurs at the moment of fracture, producing seismic waves, is an earthquake.
• The two sides of the fault lurch into new positions, moving distances ranging from centimetres to several metres, and release enormous amounts of seismic energy to the surrounding crust.

Question 41

Explain the two categories of seismic waves and their subgroups.

Answer 41

— Body waves travel through the interior of Earth and are either:

• P-waves cause ground to move back and forth in direction of travel. They are called primary waves because they are the first to arrive at seismic recording stations. Can travel through solids, liquids and gasses.
• S-waves shake the ground up and down or side to side. The are called secondary waves because they arrive after P-waves. They can only travel through solid materials.

— Surface waves are slower than body waves, but are much larger and more destructive. They are either:

• Love waves that move the ground side to side.
• Rayleigh waves that move the ground in an elliptical pattern, similar to ocean waves.

Question 42

How are earthquakes measured?

Answer 42

We use three different scales to measure the strength of earthquakes :

THE RICHTER SCALE…
- The Richter Scale measures an earthquake’s strength according to the amount of energy released during the event. The energy is measured using a seismograph.
- The Richter Scale runs from 2.4 or less to over 8.0. It is a logarithmic scale, which means that one number higher on the scale represents a wave amplitude 10-times higher on the seismograph (which is more than a 30-times increase in released energy).

THE MOMENT MAGNITUDE SCALE (MMS)…
- The Moment Magnitude Scale (MMS) was introduced in 1979 and is now the most commonly used method of measuring earthquakes.
- Like the Richter Scale, it measures the energy released by an earthquake on a logarithmic scale. But the assessment of energy is based on the amount of rock movement along a fault or fracture, and the area of the fault or fracture surface.
- Scientists think that this is a more accurate way of measuring and comparing earthquakes.

THE MERCALLI SCALE…
- The Mercalli Scale takes a different approach. Instead of scientifically measuring the amount of energy released by an earthquake, the Mercalli Scale focuses on the effects that an earthquake has on people and the environment.
- It can be done through observation, rather than needing scientific measuring equipment.

Question 43

Why might we measure earthquakes?

Answer 43

• To allow seismologists and other scientists to develop their understanding of earthquakes and their causes.
• To allow us to make meaningful comparisons between earthquakes to make planning and risk assessment more meaningful and effective.
• To help evaluate the effectiveness of earthquake management.

Question 44

Explain the term ‘risk assessment’.

Answer 44

Involves judging the amount of damage an area might expect from any given hazard.

Question 45

Define the term ‘preparation’.

Answer 45

Actions taken before a hazard strikes to reduce its impact, such as educating people or improving building design.

Question 46

Define the term ‘prediction’.

Answer 46

Being able to say when and where a natural hazard will strike. This can be done, to some extent for volcanic eruptions and hurricanes, but not for earthquakes.

Question 47

Define the term ‘monitoring’.

Answer 47

Recording physical changes, such as earthquake tremors around a volcano or tracking a hurricane by satellite, to help predict when and where a natural hazard might strike.

Question 48

Explain the primary impacts of an earthquake.

Answer 48

• Collapsed buildings and people killed or injured by falling mass.
• Broken water, gas and sewage pipelines.
• Downed electric power lines.
• Fires

Question 49

Explain the secondary impacts of an earthquake.

Answer 49

• Compensation for loss of property - insurance costs.
• Tsunamis
• Migration
• Mass homelessness.
• Spread of disease.
• Poor transport links due to mass destruction and landslides.
• Economic collapse.