Volcanic hazards

Outline the concept of mitigation in relation to the management of hazards.

Figure 9 is in the insert.

Figure 9 shows information about wildfires in Australia.

To what extent does Figure 9 show that wildfires are increasing in intensity and severity?

Figure 10 is in the insert.

Figure 10 shows information about areas at risk following a seismic event based upon underlying geology in Waikato District and the surrounding area, New Zealand.

Using Figure 10 and your own knowledge, discuss likely approaches to seismic hazard management in this area.

How far do you agree that mudflows are more hazardous than nuées ardentes?

With reference to a hazardous location at a local scale, assess the importance of the physical processes and factors which have contributed to the scale and nature of the hazard.

Outline factors which lead to the formation of mudflows, a volcanic hazard.

Figure 9 is in the insert.

Figure 9 shows responses by some companies and individuals to the Haiti earthquake, 2010.

Analyse the data shown in Figure 9.

Figures 10a, 10b and 10c are in the insert.

Figures 10a, 10b and 10c show data related to coastal flooding risk in Louisiana, USA, based upon a 2017 master plan. The information is based upon a 1 in 100 year extreme flood event.

Using Figures 10a, 10b, 10c and your own knowledge, assess the challenges in managing flood risk associated with tropical storms in Louisiana.

Assess the usefulness of prediction in the management of wildfire.

‘Seismic hazards will always be harder to manage than volcanic hazards due to their unpredictability and scale.’

To what extent do you agree with this view?

Outline the concept of the Hazard Management Cycle.

Figures 9a – 9d are in the insert.

Figures 9a – 9d show information about volcanic eruptions.

Assess the usefulness of Figures 9a – 9d in presenting information on volcanic eruptions.

Figure 10 is in the insert.

Figure 10 shows information about the 2010 earthquake in Haiti.

Using Figure 10 and your own knowledge, assess the challenges in managing an event such as this.

How far do you agree that global governance is crucial in meeting the challenge of reducing incidence of wildfires?

To what extent does plate tectonic theory help in understanding the development of landforms associated with plate movement?

What is an appropriate measure to tackle the spread of wildfire?

A In higher income countries, insurance is available. Whilst this can be very costly, it does mean that any damage done during the event can be quickly rectified.

B Replanting trees in fire-affected areas can quickly return the area to its original condition, thus preventing the spread of fire in any future event.

C Education and warning systems can provide invaluable information to people in fire prone areas. Lookouts and regular patrols can help with early evacuation.

D Use of retardants combined with controlled burning can contain a wildfire, provided this is well planned and co-ordinated in advance of the event.

What is an island arc?

A Where oceanic plates collide, subduction leads to increased friction and melting. The less dense material begins to rise through the crust, creating a series of volcanic islands.

B Radioactive elements beneath the crust cause intense heating, often away from plate boundaries. As the volcano breaks through the crust and crust moves, an arc is formed.

C As plates diverge, magma is forced to the surface. After subsequent underwater eruptions, eventually island arcs are formed along ridges, such as in the Mid Atlantic.

D As continental plates collide, enormous pressure is exerted and folding occurs. Where folding occurs in coastal locations, some land can be cut off by the sea leading to arc formation.

What is the process of slab pull?

A At constructive plate boundaries, convection currents cause plates to pull apart. This generates both seismic and volcanic activity.

B At conservative plate margins, plates are pulled alongside each other. This generates seismic activity after a period of pressure build-up.

C At destructive margins gravity forces lithosphere to descend into the mantle. The collision with the other plate causes both shallow and deep seismic activity.

D At constructive plate margins, plates are pulled apart leading to the formation of rift valleys. These valleys continue to widen and generate significant seismic activity.

Which is the method for measuring the size of a volcanic eruption?

A Volcanoes can be monitored by considering the seismic activity and the amount of gases being released. Infrared cameras can also be used to detect magma movement.

B A logarithmic scale where the energy release is proportional to the scale of the event. Each unit of increase on the scale equates to approximately 30 times the increase in energy, mainly felt through vibration.

C A qualitative scale which measures the impact of the event. The scale has 12 points. At each point there is a description which increases in severity through to total destruction.

D A logarithmic scale which offers an indication of the explosiveness of events. It is a way of classifying events by volume of material produced and frequency of events.

Figures 9a and 9b are in the insert.

Figure 9a shows data related to the eruption of K lauea Volcano, Hawai’i, USA, on 24 May 2018.

Figure 9b shows a satellite image of the same eruption.

Using Figure 9a and Figure 9b, analyse the data shown.

Figure 10 shows a wildfire on Saddleworth Moor, Greater Manchester, UK on 27 June 2018.

Note: Saddleworth Moor is an upland area north east of Manchester. The soils are composed of peat. In June 2018, there was a heatwave which was accompanied by virtually no rain and a dry wind for several weeks. Around 150 soldiers and firefighters were called in to tackle the blaze. The blaze lasted for weeks and may have been started deliberately.

Using Figure 10 and your own knowledge, assess the potential issues associated with managing an event such as this.

To what extent do you agree that the impact of volcanic activity can be mitigated against more effectively than tropical storms?

Assess the relative usefulness of the Park Model and the Hazard Management Cycle in understanding the impact of seismic events.

What are the main characteristic processes operating at destructive plate boundaries?

A Opposing convection currents lead to the divergence of plates. As plates pull apart magma intrudes leading to the formation of ridges.

B As plates slide past each other, fault lines emerge which, following the build-up of substantial pressure, lead to the development of major earthquakes.

C Subduction occurs where two plates converge. Subduction can lead to the formation of features such as deep sea trenches and island arcs.

D Radioactive decay is the main process. As the plate slides over the place experiencing the decay, the magma is forced through the plate leading to the formation of island chains.

Which of the volcanic hazards is being appropriately managed?

A The nuée ardente can be sprayed with sea water. This dramatically reduces the temperature of the gases contained within the cloud, leading to significantly reduced risk.

B Lahars can be controlled by geological surveys and drilling to stabilise hillslopes in affected areas. This reduces the likelihood of rockfall.

C In certain types of eruptions, lava can be safely channelled away from places of high risk. This can be achieved using explosives and artificially dug channels.

D Liquefaction can be managed by geological surveys which can be used to create hazard maps. These maps can then be used by planners to create exclusion zones.

Which is the most significant natural factor leading to the spread of a wildfire?

A Unplanned human activities in natural locations. These activities, such as smoking or campfires, often combine with the dropping of materials which are combustible.

B Lightning strikes, particularly in areas of dense population that have very dry conditions in summer months. California is one such state in the USA.

C Controlled burning by farmers undertaken to remove scrub land which may have been left fallow. This removes large areas of vegetation and allows for the planting of crops.

D Prolonged periods of drought and high rates of evapotranspiration, especially in the summer months in sub-tropical climates. A strong dry wind increases the risk.

What are the characteristics of tsunamis?

A They have a short wavelength and high amplitude. They travel at low speed, at around 30 km/h. They decrease in height as they approach land.

B They have a long wavelength and low amplitude. They travel at high speeds, sometimes over 700 km/h. Shallow water and the funnelling effect of bays dramatically increases height.

C They have a short wavelength and consist of a series of waves. They strike land in quick succession with heights sometimes exceeding 20 metres.

D Strong winds whip up large waves which lead to very powerful waves. The funnelling effect of bays creates super-sized waves.

Figure 9, on the insert, shows data related to seismic activity and vertical motion in the Yellowstone caldera in the USA. Sour Creek (SC) is a resurgent dome in the Yellowstone caldera in the USA. A resurgent dome is formed by swelling or rising of a caldera floor due to movement in the magma chamber beneath it.

Figure 10, on the insert, shows a map of Yellowstone: volcanic vents active since the last caldera collapse 640 000 years ago; earthquakes recorded between 2003 and 2008; faults; and ground deformation between 2004–2006.

Analyse the data shown in Figure 9 and Figure 10.

How far do you agree that secondary impacts of volcanic eruptions present a greater long-term threat to people than primary impacts?

With reference to one or more tropical storms that you have studied, assess the extent to which exogenous factors (relationships with other places) assisted with the response to the hazard created.

With reference to a multi-hazardous environment that you have studied, assess the view that the underlying cause(s) leading to the hazards is human activity rather than physical factors.