Geography Yr 9 Autumn CAT Revision

Natural hazard

A natural event (such as an earthquake, volcanic eruption, tropical storm, or flood) that threatens people or has the potential to cause damage, destruction, and death.

Hazard risk

The probability or chance that a natural hazard may take place and cause harm to people or property.

Three factors affecting hazard risk

1. Hazard Type: The severity, scale, and frequency of the event.
2. Exposure: The number of people and value of property located in hazard-prone areas.
3. Vulnerability: The capacity of a community to cope with, resist, and recover from the hazard.

Plate tectonics theory

The theory that the Earth's crust is broken into large slabs called tectonic plates, which float on the semi-molten mantle and move slowly due to convection currents.

Igneous rocks

Rocks formed when molten magma or lava cools and solidifies, either beneath the Earth's surface or following a volcanic eruption.

Sedimentary rocks

Rocks formed from deposited mineral and organic particles that are compressed and cemented into layers over long periods, typically in water bodies.

Metamorphic rocks

Existing rocks transformed by intense heat and pressure, typically deep underground or along tectonic plate boundaries.

Pacific "Ring of Fire"

A major horseshoe-shaped belt tracing the margins of the Pacific Ocean where the majority of the world's earthquakes and volcanic eruptions occur.

Volcanic hotspot

An area of intense volcanic activity occurring away from plate boundaries, often in the middle of a tectonic plate (e.g., the Hawaiian Islands).

Constructive plate margin

A plate boundary where two tectonic plates diverge (pull apart), allowing magma to rise, cool, and create new crust, producing volcanoes and minor earthquakes.

Destructive plate margin

A plate boundary where plates collide, forcing the denser oceanic plate beneath the continental plate (subduction) to melt into magma, resulting in explosive volcanoes and powerful earthquakes.

Conservative plate margin

A plate boundary where two plates slide past one another at varying speeds; friction causes them to lock until the stored pressure releases as severe earthquakes with no volcanic activity.

Primary effects of a tectonic hazard

The direct, immediate impacts caused by the hazard itself as it occurs (e.g., buildings collapsing and ground shaking during an earthquake).

Secondary effects of a tectonic hazard

Indirect after-effects triggered by the primary impacts, often developing over a longer timescale (e.g., fires from ruptured gas mains, tsunamis, or disease outbreaks).

Immediate responses vs. Long-term responses

• Immediate responses: Emergency actions taken during the event and in its direct aftermath, including search and rescue and providing emergency shelter.
• Long-term responses: Rebuilding, structural repair, and socio-economic restoration taking place weeks, months, or years later.

Haiti Earthquake (2010) case details

• Classification: Low-Income Country (LIC)
• Magnitude: $7.0$
• Impacts: Around $230{,}000$ deaths, $1.3\text{ million}$ homeless, and widespread structural collapse.
• Responses: Relied heavily on international search-and-rescue teams and humanitarian aid; reconstruction remained slow due to extreme poverty.

Japan Tohoku Earthquake and Tsunami (2011) case details

• Classification: High-Income Country (HIC)
• Magnitude: $9.0$
• Impacts: Approximately $19{,}759$ deaths, a $40\,\text{m}$ tsunami, the Fukushima nuclear disaster, and over $\$200\text{ billion}$ in economic damage.
• Responses: Immediate automated warnings, rapid military deployment, and quick self-funded reconstruction utilizing advanced infrastructure.

Reasons people choose to live in tectonic risk zones

• Fertile soils: Weathered volcanic ash produces nutrient-rich land for agriculture.
• Economic opportunities: Geothermal energy, mining resources, and tourism create employment.
• Socio-economic factors: Poverty limits the ability to relocate, while cultural and familial heritage ties people to their homes.

Four management strategies for tectonic hazards (3Ps + M)

• Monitoring: Using scientific tools like seismometers to detect earth tremors and volcanic gas emissions.
• Prediction: Forecasting the timing and location of hazards to enable warnings.
• Protection: Engineering earthquake-resistant structures with reinforced frames and shock absorbers.
• Planning: Mapping high-risk zones, holding evacuation drills, and stockpiling emergency supplies.

Continental crust vs. Oceanic crust

• Oceanic crust: Thinner, denser, and subducts at destructive plate boundaries.
• Continental crust: Thicker, less dense, and does not subduct.