Geography

Natural hazard

A natural event (like an earthquake, storm, or flood) that poses a threat to human life, property, or infrastructure.

Hazard risk

The probability or chance that people will be harmed or damaged by a natural event.

Factors influencing hazard risk

Key factors like urbanisation, poverty, climate change, and high population density that make communities more vulnerable.

Plate tectonics theory

The idea that Earth's outer layer, the lithosphere, is broken into giant pieces called tectonic plates that float on the semi-molten mantle beneath.

Global distribution of earthquakes and volcanoes

Mainly found along tectonic plate boundaries, such as around the edge of the Pacific Ocean in the Pacific Ring of Fire.

Constructive (divergent) plate margin

A boundary where two plates move apart, allowing magma to rise and cool to create new crust, causing mild earthquakes and shield volcanoes.

Destructive (convergent) plate margin

A boundary where a heavy oceanic plate sinks under a continental plate, creating violent earthquakes and steep composite volcanoes.

Conservative (transform) plate margin

A boundary where two plates slide horizontally past each other, building up friction that releases as severe earthquakes with no volcanoes.

Primary effects of a tectonic hazard

Direct damage caused immediately during the event, such as ground shaking, collapsed buildings, broken pipes, and deaths.

Secondary effects of a tectonic hazard

Problems that happen later on as a result of primary damage, including tsunamis, fires from gas leaks, landslides, and disease outbreaks.

Immediate responses to a tectonic hazard

Quick short-term actions taken during or straight after the disaster, like rescuing survivors, setting up temporary shelter, and providing clean drinking water.

Long-term responses to a tectonic hazard

Actions taken months or years later to help recovery, such as rebuilding homes, repairing roads, and restoring the economy.

Monitoring tectonic hazards

Using scientific instruments like seismometers and gas detectors to spot early warning signs of tectonic activity.

Predicting tectonic hazards

Using historical records and monitoring trends to estimate when and where a hazard might occur (much easier for volcanoes than earthquakes).

Protecting against tectonic hazards

Designing earthquake-resistant buildings with features like rubber shock absorbers, reinforced steel frames, and automatic shut-off valves.

Planning for tectonic hazards

Preparing populations in advance through earthquake drills, mapping evacuation routes, and storing emergency kits.

Why people live in tectonic risk areas

Due to benefits like fertile volcanic soils for farming, geothermal power, job opportunities in tourism, or simply having no money to move.

Global atmospheric circulation model

A global wind system driven by the sun's heat, divided into three atmospheric cells: the Hadley, Ferrel, and Polar cells.

High-pressure belt conditions

Created by sinking air, leading to clear skies, low rainfall, and dry weather (found around $30^\top\text{N/S}$ latitude).

Low-pressure belt conditions

Created by rising air, which cools and condenses to form clouds and heavy rain (found at the Equator).

Conditions needed for tropical storm formation

Requires ocean temperatures of at least $27\,^\top\text{C}$, water depth of $60\,\text{m}$, and a location between $5^\top\text{--}15^\top$ latitude where the Coriolis effect is strong.

Sequence of tropical storm formation

Warm moist air rises, condenses into large thunderstorms, releases heat that lowers air pressure further, and spins due to the Coriolis effect.

Structure of a tropical storm: Eye

The very centre of the storm where air sinks, creating calm weather, light winds, and no rain.

Structure of a tropical storm: Eyewall

The ring of dense clouds surrounding the eye with the storm's strongest winds, heavy rainfall, and powerful rising air.

Impact of climate change on tropical storms

Warmer sea temperatures can make storms more intense, cause higher rainfall amounts, and allow storms to form over a wider geographic area.

Types of weather hazards in the UK

Includes heavy rainfall and flooding, extreme cold and snow, high gales, heatwaves, and prolonged droughts.

Quaternary period

The current period of geological time covering the last $2.6\text{ million years}$, characterised by cycles of ice ages (glacials) and warmer periods (interglacials).

Evidence for historical climate change

Information gathered from ice core samples (trapped gas bubbles), tree rings, ocean sediments, and thermometer records.

Natural causes of climate change

Includes Milankovitch cycles (changes in Earth's orbit), volcanic eruptions blocking sunlight, and changes in solar output.

Human causes of climate change

Burning fossil fuels, deforestation (cutting down forests), farming (releasing methane), and making cement.

Climate change mitigation

Actions taken to stop or reduce the causes of climate change, such as using renewable energy or planting trees.

Climate change adaptation

Actions taken to adjust human lifestyles to cope with the unavoidable impacts of climate change, such as building sea walls.

Carbon capture and storage (CCS)

A mitigation strategy that traps carbon emissions from industrial power plants and stores them deep underground.

Ecosystem

A community of living organisms (biotic) interacting with each other and their non-living environment (abiotic).

Biotic vs Abiotic elements

Biotic factors are living parts of an ecosystem (plants, animals); Abiotic factors are non-living physical parts (climate, soil, water).

Producer in an ecosystem

An organism (usually green plants) that makes its own food using energy from the sun through photosynthesis.

Decomposer

An organism (like bacteria or fungi) that breaks down dead plants and animals, recycling nutrients back into the soil.

Nutrient cycling stores (Gersmehl model)

The transfer and storage of nutrients between three key reservoirs: Biomass (living matter), Litter (fallen organic matter), and Soil.

Tropical rainforest physical characteristics

Warm temperatures year-round ($\approx 27\,^\top\text{C}$), very high rainfall ($>2000\,\text{mm/yr}$), dense multi-layered trees, and high biodiversity.

Latosol soil features

A deep, reddish, nutrient-poor soil in rainforests that is washed out by heavy rainfall (leached) and relies on rapid leaf decay for nutrients.

Drip tip leaf adaptation

Leaves with smooth waxy surfaces and sharp points that allow rainwater to drip off quickly without snapping the leaf.

Buttress root adaptation

Large, wide surface roots that support very tall rainforest trees in shallow soil.

Main causes of tropical rainforest deforestation

Clearing land for cattle ranching, soy and palm oil farming, commercial logging, mining, and building roads.

Selective logging

A sustainable practice where only fully grown or specific trees are chopped down, keeping the forest canopy intact.

Debt-for-nature swaps

Agreements where a country has part of its financial debt forgiven in return for protecting its rainforest areas.

Hot desert location factors

Located between $15^\top\text{ and }30^\top\text{ N/S}$ of the Equator, under permanent high-pressure belts of sinking air.

Adaptations of xerophytic plants

Features like thick waxy outer layers, spines instead of leaves to reduce water loss, deep roots, and fleshy stems to store water.

Desertification

The process where land gradually degrades and turns into dry, barren desert.

Primary drivers of desertification

Overgrazing, over-cultivation of crops, cutting down trees for fuel, population pressure, and long periods of drought.

Appropriate technology for desertification

Simple, low-cost solutions like stone bunds (low walls) built along contours to slow rain runoff and trap rich soil.

Polar vs Tundra environments

Polar regions are permanently covered in ice and snow with sub-zero weather; Tundra regions thaw slightly in summer, allowing small plants to grow.

Permafrost

Layer of ground or soil that stays completely frozen below $0\,^\top\text{C}$ for at least two consecutive years.

Constructive wave profile

Gentle waves with a strong swash and weak backwash that build up beaches by depositing sand and shingle.

Destructive wave profile

Tall, steep waves with a weak swash and strong backwash that erode the coast by pulling sediment out to sea.

Mechanical (physical) weathering

Physical breakdown of rock without changing its chemical makeup, such as freeze-thaw weathering.

Chemical weathering

Breakdown of rock caused by chemical reactions, such as carbonation when acidic rain dissolves limestone rock.

Rotational slumping

A type of mass movement where heavy, wet soil and rock slide downwards along a curved slip surface.

Hydraulic action

Erosion caused by the force of waves crashing into cracks, trapping and compressing air until the rock shatters.

Abrasion process

The sandpapering effect where rocks carried by water or ice scrape forcefully against rock surfaces.

Attrition process

The process where rocks carried by water collide with each other, breaking into smaller, rounder pebbles.

Longshore drift

The movement of sand and shingle along a beach in a zigzag pattern, driven by waves arriving at an angle.

Formation of headlands and bays

Forms along coasts with alternating rock types: soft rock erodes quickly to form bays, while hard rock erodes slowly to form headlands.

Erosional sequence: Crack to Stump

Crack $\rightarrow$ Cave (widened by erosion) $\rightarrow$ Arch (breaks through) $\rightarrow$ Stack (roof collapses) $\rightarrow$ Stump (stack falls).

Formation of a coastal spit

A long ridge of sand or shingle formed when longshore drift carries sediment past a bend in the coastline and deposits it in calm water.

Hard vs Soft engineering approach

Hard engineering uses artificial man-made structures to stop natural forces; Soft engineering uses natural processes to manage risks sustainably.

Coastal Groynes

Wooden or concrete fences built at right angles to the shore to trap sediment carried by longshore drift, keeping beaches wide.

Managed retreat (Coastal realignment)

Intentionally allowing low-value coastal land to flood naturally, creating salt marshes to absorb wave impact.

River upper course profile

Features steep gradients, narrow V-shaped valleys, and dominant vertical (downward) erosion.

River lower course profile

Features flat land, wide channels, large volume of water, and dominant lateral (sideways) erosion and deposition.

Waterfall and gorge formation

Water flows over hard rock sitting on soft rock. Soft rock erodes to form an undercut overhang, which collapses, causing the waterfall to retreat upstream leaving a gorge.

Oxbow lake formation

A meander loop is cut through during a flood, creating a straight path; sediment eventually blocks off the old loop to form a curved lake.

River Levée formation

Natural raised riverbanks built up when repeated flooding causes a river to drop its heaviest sediment right along its banks.

Hydrograph lag time

The time gap between the peak rainfall and the peak river discharge.

Factors increasing river flood risk

Heavy or prolonged rain, impermeable bedrock (water cannot sink in), steep slopes, deforestation, and concrete surfaces in towns.

Floodplain zoning

A soft engineering method that restricts building on land near rivers that is prone to flooding.

Freeze-thaw weathering sequence

Water gets into cracks $\rightarrow$ freezes and expands by 9\% $\rightarrow$ puts pressure on the rock $\rightarrow$ repeated cycles cause the rock to split apart.

Plucking (Glacial erosion)

Meltwater freezes around loose rocks on the valley floor and tears them away as the glacier moves forward.

Corrie (Cirque) formation

Snow collects in a hollow, turns into ice, and rotational slip deepens the hollow via plucking and abrasion, leaving a steep backwall.

Arête

A sharp, knife-edged ridge created when two adjacent corries erode back-to-back into the same mountain.

Pyramidal peak

A pointed mountain peak formed when three or more corries erode backward against each other.

Glacial trough (U-shaped valley)

A steep-sided, flat-bottomed valley formed as a powerful glacier carves its way down an existing V-shaped river valley.

Drumlin landform

An elongated, egg-shaped hill of glacial deposit that points in the direction the glacier was moving.

Moraine classifications

Debris deposited by ice, classified as Lateral (valley sides), Medial (middle confluence), Terminal (furthest point reached), or Ground (valley floor).

Glacial erratic

A large rock or boulder carried by a glacier and deposited in an area with a completely different underlying rock type.