OCR GCSE Geography B (J384) — Global Hazards
Why does a magnitude 7.8 earthquake in one country cause utter devastation, while a stronger magnitude 9.0 earthquake elsewhere results in fewer collapsed buildings?
The answer lies in the relationship between the physical power of the tectonic hazard and the human vulnerability of the location. We can explore this by looking at a major tectonic event: the 2015 Gorkha earthquake in Nepal, a Low-Income Developing Country (LIDC).
The disaster struck on the 25th of April 2015, with a magnitude of 7.8. Its epicentre was in the Gorkha district, just 80 km northwest of the capital, Kathmandu.
This event was caused by a collision plate margin. The Indian Plate is constantly moving northwards at a rate of roughly 45 mm per year, crashing into the Eurasian Plate.
Because both are continental plates, neither undergoes subduction (meaning this boundary does not produce volcanoes). Instead, the immense friction causes them to lock together, building massive pressure until it is violently released as seismic waves from a shallow focus just 8.2 km underground.
The impacts of a tectonic event are split into primary impacts (direct results of the ground shaking) and secondary impacts (knock-on effects).
Nepal's devastating death toll was heavily influenced by its status as an LIDC. We can understand this using the Hazard Risk Equation:
Nepal's vulnerability was exceptionally high because it is a very poor, landlocked nation with a GDP of less than $1,000 per capita at the time. This lack of wealth meant buildings were not heavily earthquake-proofed, unlike those in an Advanced Country (AC) like Japan, which heavily lowered Nepal's capacity to cope.
Furthermore, Kathmandu is built on ancient lakebed sediments. The intense shaking caused liquefaction, where solid ground temporarily acts like a liquid, massively amplifying the destruction of infrastructure.
Short-term responses focus on immediate survival and rescue. The Nepalese Army rapidly mobilised 90% of its personnel, while the Red Cross distributed 50,000 tents to those displaced.
Long-term responses involve mitigation and recovery. The Asian Development Bank (ADB) provided $200 million for rebuilding efforts, which helped restore 7,000 schools.
Students often confuse primary and secondary impacts. Remember, an avalanche (secondary) happens because of the ground shaking (primary) — it is not the direct shaking itself.
For 6 or 8-mark 'Analyse' or 'Evaluate' questions, you must use specific data (e.g., '10 billion economic cost') rather than vague statements like 'it cost a lot of money' to access Level 3 marks.
Use the CLEVER framework (Causes, Location, Effects, Vulnerability, Evaluation, Responses) to quickly plan your extended writing on any tectonic case study.
Always explicitly link the scale of damage back to the country's development level; examiners want to see you explain why the death toll was high in an LIDC, using concepts like wealth, infrastructure, and the Hazard Risk Equation.
Vulnerability
The inability of a community or location to withstand, cope with, or recover from a natural hazard.
Low-Income Developing Country (LIDC)
A poorer country with a low Gross National Income (GNI) per capita and a low Human Development Index score.
Epicentre
The point on the Earth's surface directly above where an earthquake originates.
Collision
A type of convergent plate boundary where two continental plates crash into each other, crumpling to form fold mountains without creating volcanoes.
Subduction
The geological process where a denser oceanic plate is forced down into the mantle beneath a less dense tectonic plate.
Focus
The exact point inside the Earth's crust where an earthquake originates and seismic energy is first released.
Primary impacts
The immediate, direct effects of a hazard, such as buildings collapsing directly from the ground shaking.
Secondary impacts
The knock-on or indirect effects of a disaster that occur later, such as landslides, disease outbreaks, or economic loss.
Sedimentation
The process of rock and soil particles settling at the bottom of a water body, which can reduce river capacity and increase future flood risks.
Glacial Lake Outburst Floods (GLOFs)
A sudden, dangerous flood occurring when the natural dam containing a glacial lake fails, often triggered by seismic activity.
Advanced Country (AC)
A wealthier nation with a high Human Development Index score and sophisticated, resilient infrastructure.
Liquefaction
A process where intense earthquake shaking causes water-saturated sediment to temporarily lose strength and behave like a fluid.
Mitigation
Actions taken before or after a disaster to reduce or eliminate long-term risks to people and property from future hazards.
Short-term responses
Actions taken in the immediate aftermath of a disaster (days/weeks) to save lives and provide basic needs.
Long-term responses
Actions taken months or years after a disaster to rebuild infrastructure and reduce future risk.
Indian Plate
A major tectonic plate that is moving northwards into the Eurasian Plate, forming the Himalayas.
Eurasian Plate
A large tectonic plate that covers most of Europe and Asia.
Hazard Risk Equation
A formula used to calculate the level of risk a community faces from a natural event.
Capacity to Cope
The ability of a community to use available resources to manage and recover from a disaster.
Put your knowledge into practice — try past paper questions for Geography B
Vulnerability
The inability of a community or location to withstand, cope with, or recover from a natural hazard.
Low-Income Developing Country (LIDC)
A poorer country with a low Gross National Income (GNI) per capita and a low Human Development Index score.
Epicentre
The point on the Earth's surface directly above where an earthquake originates.
Collision
A type of convergent plate boundary where two continental plates crash into each other, crumpling to form fold mountains without creating volcanoes.
Subduction
The geological process where a denser oceanic plate is forced down into the mantle beneath a less dense tectonic plate.
Focus
The exact point inside the Earth's crust where an earthquake originates and seismic energy is first released.
Primary impacts
The immediate, direct effects of a hazard, such as buildings collapsing directly from the ground shaking.
Secondary impacts
The knock-on or indirect effects of a disaster that occur later, such as landslides, disease outbreaks, or economic loss.
Sedimentation
The process of rock and soil particles settling at the bottom of a water body, which can reduce river capacity and increase future flood risks.
Glacial Lake Outburst Floods (GLOFs)
A sudden, dangerous flood occurring when the natural dam containing a glacial lake fails, often triggered by seismic activity.
Advanced Country (AC)
A wealthier nation with a high Human Development Index score and sophisticated, resilient infrastructure.
Liquefaction
A process where intense earthquake shaking causes water-saturated sediment to temporarily lose strength and behave like a fluid.
Mitigation
Actions taken before or after a disaster to reduce or eliminate long-term risks to people and property from future hazards.
Short-term responses
Actions taken in the immediate aftermath of a disaster (days/weeks) to save lives and provide basic needs.
Long-term responses
Actions taken months or years after a disaster to rebuild infrastructure and reduce future risk.
Indian Plate
A major tectonic plate that is moving northwards into the Eurasian Plate, forming the Himalayas.
Eurasian Plate
A large tectonic plate that covers most of Europe and Asia.
Hazard Risk Equation
A formula used to calculate the level of risk a community faces from a natural event.
Capacity to Cope
The ability of a community to use available resources to manage and recover from a disaster.
