Part 2. Geophysical Hazard Risks

Conceptual Understanding:

Key Question:

How do geophysical systems generate hazard risks for different places?

Key Content:

  • The distribution of geophysical hazards (earthquakes, volcanoes, mass movements)
  • The relevance of hazard magnitude and frequency/recurrence for risk management
  • Geophysical hazard risk as a product of economic factors (levels of development and technology), social factors (education, gender), demographic factors (population density and structure) and political factors (governance)
  • Geographic factors affecting geophysical hazard event impacts, including rural/urban location, time of day and degree of isolation

Monday 05 February 2024

The distribution of geophysical hazards…

Starter: Watch the animated video below that displays all recorded earthquakes between the year 2000 – 2015. Watch carefully for the 2004 Indonesian earthquake that caused the devastating tsunami as well as the Japanese quake and tsunami of 2011. 

Distribution of Earthquakes, Volcanoes and Mass Movement Events


Volcanic activity takes place at convergent boundaries, where one plate is subducted under another. This may be oceanic to oceanic or oceanic to continental. In the former, submarine volcanoes erupt to produce island arcs, like that of the Aleutian Island Arc off Alaska. The latter produces significant volcanic mountain ranges such as the Andes, which forms from the subducting Nazca plate under South America. Composite volcanoes have low frequency eruptions but can be very explosive in their eruption. At subductive boundaries the more destructive composite volcanoes are more common. These are the result of high silicate magma rising upwards through the continental crust. Volcanoes also form at hotspots and divergent plate boundaries, where shield volcanoes are more common. Shield volcanoes like that of Mauna Loa in Hawaii are low in silica and produce fast flowing low viscosity lava. Shield volcanoes have high frequency eruptions but tend to have much lower explosivity compared to composite volcanoes.


Earthquakes occur at all plate boundaries and also occur within vast plate boundary zones that can stretch several thousand kilometers away from the boundary, along transform faults and associated micro faults. High frequency, low magnitude earthquakes are more associated with conservative plate boundaries such as the San Andreas Fault in California. These earthquakes tend to be shallow in nature and low magnitude but conservative boundaries can also produce much higher magnitude earthquakes but at lower frequency.

High magnitude earthquakes tend to be associated more with deeper earthquakes, related to subduction zones. The Pacific Ring of Fire is not only associated with its explosive volcanic activity but also with high magnitude earthquakes. These earthquakes tend to be lower in frequency. However, some geologists argue that the highest magnitude earthquakes tend to come in twos. Although there is limited statistical evidence to support this, what is clear, is that large earthquakes often cluster with many aftershocks, some of which can be almost as severe as the first.

Mass Movement Events

Mass movement events can occur anywhere in the world but there is a higher risk in steep mountainous regions with coarse soil. Landslide risk is greatest in populated regions with high rainfall events, such as tropical storms and lead to slope saturation and river flooding. In addition regions experiencing population pressure, deforestation , road construction, mining and plantations all lead to greater risk of landslides.

Describing Maps, Photos and Graphs

We are now going to practice describing maps, photos and graphs whilst consolidating our understanding of where different geophysical hazards occur.

On the desks are a range of exam style questions concerning the distribution of geophysical hazards based on different maps, photos and graphs.

  1. Study the different resources provided.
  2. Choose six questions that you would like to answer.
  3. You must anaswer at least one question on each of the geophysical hazards we have studied – earthquakes, volcanoes and mass movement.
  4. Answer the six questions on a Google Doc.

Assessment 1.1 | Resources (Google Doc)

Thursday 08 February 2024

Measuring Hazards and Managing Hazard Risk…

In this section, we will briefly look at how we measure hazards, followed by the relevance of hazard magnitude and frequency/recurrence for risk management, that is, how can we use the past to try to predict the future. 

Task 1. Using the information on the Google Doc, create 5 questions (with answers) that you can ask your peers on these scales.

Lesson 3. Measuring and Monitoring Hazards (Google Doc)

Task 2. The videos below will focus on the following case studies. 

1. Earthquake – Using past events to manage future risk in Istanbul, Turkey. 

2. Volcano – How we can predict volcanic eruptions (Hawaii, followed by predictions for the future, Naples, Italy) 3.30 – 18.30 of video. 

3. Landslide – Historical events and monitoring by NASA. 

Take notes on all three areas below in order to answer the following 6 mark question:

Distinguish between the strategies used to manage the risks of geophysical hazards (6). 

Managing Risk – Earthquakes
Managing Risk – Volcanoes
Managing Risk – Landslides

Monday 12 February 2024

​Risk as a product of geographic, social, economic, demographic & political factors…

Task 1. You have 10 minutes to answer the following 6 mark question:

Distinguish between the strategies used to manage the risks of geophysical hazards (6 marks).

Hazard Risk and Vulnerability

Starter: Study the photograph below and comment on any factors that make people more at risk of hazards.

Task 1. On this Google Doc match the definition to the correct key term.

Hazard Risk Equation

The risk of being impacted by a natural hazard depends upon the type of hazard occurring and the concept of vulnerability. Vulnerability not only includes the physical effects of a natural hazard but also the status of the people and the property in the affected area. A number of factors can increase people’s vulnerability to natural hazards. These include:

  • Geographic factors
  • Social factors
  • Economic factors
  • Demographic factors
  • Political factors

Task 2. Today we will be investigating risk as a product of the above factors. We will be completing a mind mapping exercise to explore this.

What factors do you think make some people and places more vulnerable to hazards? 

On your diagram attempt to identify the root causes, dynamic pressures and unsafe conditions that can increase the risk and vulnerability of a population to geophysical hazards.

Task 3.

Watch the following videos, and make notes on the factors that impact people’s risk of hazards.

Explain how these conditions may have been worse in a place like Haiti.

Task 4. Study the following three examples and make notes on the economic, social and political factors increasing risk. Each of you should choose a case study and be responsible for summarising one article in this document.

Case Study 1. Sichuan Province Earthquake – Adapted from a Guardian report 1 from 2009, Sichuan earthquake kills more than 5000 pupils says China

China said today that 5,335 schoolchildren and students had died or remained missing after last year’s Sichuan earthquake, the first official tally in what became a politically charged issue because of allegations of corruption and shoddy school construction.

The government began a count of the dead and missing within hours of the magnitude 7.9 quake, which destroyed huge portions of Sichuan, but authorities have refused until now to say how many pupils were killed when thousands of classrooms collapsed while buildings around them remained intact.

Liu Xiaoying, whose 12-year-old daughter was killed when the three-storey Fuxin No 2 primary school collapsed, said she was sure the toll was much higher. “I hope the investigation will continue and that the people responsible will be seriously punished,” she said. Liu is under surveillance after travelling to Beijing twice to petition the central government. “I hope the government will really do what they say they would and not brush off us parents,” she said. “If this is the case, the hearts of my husband and I will be more at ease.”

Ai Weiwei, an artist and high-profile critic of Beijing’s policies, said the announcement was a sign that the government may be caving in to “pressure of the common people, pressure from the media,” but it was still an empty gesture. “There’s no significance to this announcement because it didn’t give any names or any other information on where they died, which schools or which classes they were in,” Ai said. “This is nonsense.”

In his blog, Ai has confirmed almost 5,000 pupil names and estimates that the toll could reach 8,000. He said that at least 20 of his helpers had been detained by local authorities. Tan Zuoren, who conducted his own investigation into 64 schools in the quake zone, has estimated that more than 5,600 pupils are dead or missing. Tan, who has since been detained on suspicion of subversion, said that number was incomplete.

Case Study 2. Banda Aceh Tsunami 2004 – Adapted from the JRSM – Impact of the tsunami on reproductive health

For various reasons, women were at much greater risk of death in the Tsunami than other people. The ratio of female to male deaths was 3:1 and in some communities only women are reported to have been killed. Surviving women may also have become more vulnerable than other survivors to a range of social and economic threats, and most of those who survived have been thrust into unemployment and poverty. Unlike men in these countries, many were unaccustomed to swimming or to being in the water other than to bathe. Also, the clothes they wore and their culturally prescribed long hair became entangled in tree branches and other debris. In some coastal communities, moreover, there are stories of women running back to the beach to search for missing children when the first wave receded, only to be caught by the second wave when it struck. The vulnerability of women who survived is also an issue of concern in relation to sexual violence and rape, and with respect to their economic livelihoods.

Everywhere in the region people have been thrust back or further into poverty and for women this may be more problematic than for men. Even in the special camps, the safety of women will remain fragile.

The Tsunami affected reproductive health in many ways. It caused sex-specific death on a scale that has devastated families and family life. In doing so it placed many people in a new type of vulnerability that will require highly creative policies and strategies to overcome. It also devastated many of the healthcare services that are essential to sound antenatal care and delivery, killing large numbers of midwives in Indonesia and medical personnel in other countries, and destroying vital physical infrastructures.

In disrupting so many families and communities and causing one of the greatest displacements of people ever seen, the Tsunami also created conditions that are likely to bring new threats and challenges to women and girls. Securing their health will have to include protection as well as good quality healthcare.

Many relief organizations failed, as in previous disasters, to give adequate priority to reproductive health. The various complements are vital to individual, family and public health, and their neglect will only set back the health reconstruction effort, especially in populations where the reproductive health indicators were cause for concern even before the Tsunami.

Case Study 3. The Guinsaugon Landslide 2006 – Adapted from the PSJI Blog – What did not happen in Guinsaugon

A disaster waiting to happen. This was how the recent landslide that buried the entire village of Bgy. Guinsaugon in the municipality of St. Bernard in Southern Leyte — leaving barely a hundred survivors out of about 2,000 residents — has been largely explained to the public.

Given the condition of unstable weathered sediments and steep slopes, two weeks of unusually heavy rains proved to be the ultimate “triggering” factor. The week before the Guinsaugon disaster, the rainfall readings obtained by the Southern Leyte PAGASA station registered an amount of 571.2mm, equivalent to almost three months of the area’s average annual precipitation of 3,000 mm. Despite this measures to address both the “triggering” and “conditioning” factors were non-existent, or at the very least, not implemented.

It is not true that the causes could not have been predicted or monitored. In other countries, potential amount and intensity of incoming rain has been successfully measured using precipitation radars. A good network of rain gauges sending out near-real time data or even crude locally based rain gauges can give a warning few hours before a disaster. PAGASA, however, does not have a very good network of rain gauges in the area, much more precipitation radars. (quoting Nestor Saturay, geologist at the National Institute of Geological Sciences at the University of the Philippines in Diliman)

Knowing the general setting of the area long before the disaster in Southern Leyte, a detailed geologic hazard map could have been made. But with limited personnel and budget of the Mines and Geosciences Bureau allocated for geohazard mapping, detailed geohazard maps were not produced. Knowledge of the triggering and conditioning factors is not enough to prevent disasters. It is important for the people — the ordinary folks who are not scientists, geologists, experts who may have no idea about how a geohazard map looks — to know and understand their situation.

Nevertheless, a comprehensive disaster mitigation program at the community/barangay level, which includes geohazard information, land use planning and systematic warning and evacuation procedures, was not formulated nor implemented.

Homework: Due: Wednesday 14 February 2024

Complete the ‘Check Your Understanding’ boxes on pages 175 and 185.