How do geophysical systems generate hazard risks for different places?
- 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
Wednesday 28 September 2022
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.
Today we are going to use latitude and longitude coordinates to map a range of earthquake, volcano and mass movement events.
Task 1. Using the coloured dots provided and the coordinates sheet, map volcano, earthquake and mass movement events onto the map provided.
Lesson 1. Coordinates Sheet (Google Doc)
Thursday 29 September 2022
Starter: Using the map that you created for homework:
- Describe the global spatial distribution of volcanoes, earthquakes and mass movement events.
- Comment on the relationship between plate boundaries and the above events.
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.
Assessment 1.1 | 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.
- Study the different resources provided.
- Choose six questions that you would like to answer.
- You must anaswer at least one question on each of the geophysical hazards we have studied – earthquakes, volcanoes and mass movement.
- Answer the six questions on a Google Doc.
Assessment 1.1 | Resources (Google Doc)
Monday 03 October 2022
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).
Thursday 06 October 2022
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
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.
- Read the cards provided and sort them into one of the five categories above. You can also use the diagram below to help you.
- Summarise the cards into your copy of the hzard risk and vulnerability mindmap.
Lesson 4. Hazard Risk and Vulnerability (Google Slides)
Task 3. Choose your top 3 factors that make a population vulnerable and explain why they are so important.
Task 4. Study the map below of the Sichuan Province in China and suggest different factors relating to the area and event that would increase risk before, during and after the earthquake.
Homework: Due: Thursday 13 October 2022.
Complete the ‘Check Your Understanding’ boxes on pages 175 and 185.