AQA GCSE Geography Natural Hazards

Crust

The solid surface of the Earth

Plate

A huge section of the Earth's crust

Plate margin

The edge or boundary between two plates

Mantle

The layer of semi-molten rock below the Earth's crust

Convection currents

The circular movement of magma in the mantle due to the heat from the core

Subduction zone

The area where the oceanic plate sinks under the continental plate

Conservative margin

Two plates move side by side, neither is subducted (e.g. San Andreas fault, California)

Constructive margin

Two plates move apart (e.g. Mid-Atlantic ridge)

Destructive margin

Where oceanic plate goes under continental plate (e.g. West coast of South America)

Collision zone

Where two continental plates move towards each other, causing the rocks to buckle

Fold mountain

Mountains formed by plate movements (e.g. Himalayas, Asia)

Oceanic trench

Deep sections of the oceans, usually where oceanic plate is sinking below continental plate

Composite volcano

Steep-sided cone with layers of ash and lava (e.g. Vesuvius, Italy)

Shield volcano

Gently sloping sides, wide base, made of basic lava (e.g Mauna Loa, Hawaii)

Subsistence farming

Farming to provide food and other resources for the farmer's own family.

Terraces

Steps cut into hillsides to create areas of flat land

Irrigation

Artificial watering of the land (often using sprinklers)

Hydro-electric power (HEP)

Using flowing water to turn turbines to generate electricity

Natural hazard

An event in nature that causes harm to the people and their surroundings

Primary effects

The immediate effects or the event, caused directly by it, (e.g. water pipes burst)

Secondary effects

The after-effects that occur as an indirect effect of the event (e.g. fire)

Aid

Help

Earthquake

A shaking of the Earth's crust

Immediate response

How people react as the disaster happens and straight afterwards

Long-term response

Later reactions that occur in the weeks, months and years after the event

Crater

The opening at the top of a volcano from which magma is emitted

Lahar

Mudflow after a volcanic eruption formed by ash mixing with water or melting ice

Supervolcano

A mega colossal volcano that erupts at least 1,000km3 of material

Caldera

A depression within a volcano showing a collapsed magma chamber

Fissures

Extended openings along a line of weakness that allow magma to escape

Geothermal

Water that is heated beneath the ground by the heat of the Earth

Geosyncline

A depression in the Earth's surface (such as an ocean or large lake) in which sediments are deposited.

Hot spot

A section of the Earth's crust where plumes of magma rise, weakening the crust. Away from plate boundaries, (e.g. Hawaii)

Focus

The point in the Earth's crust where the earthquake takes place

Richter scale

Measures the strength (force of the earthquake)

Epicenter

The point at the Earth's surface, directly above the focus

Shock waves

Seismic waves generated by an earthquake that pass through the Earth's crust

Mercalli scale

Measures an earthquake by looking at the damage done on a scale of 1-12

The three Ps

Prediction, protection and preparation

Lava

Molten rock above the Earth's crust

Magma

Liquid rock below the Earth's crust

Tsunami

A wave set in motion by an earthquake

Volcano

A cone-shaped mountain created by lava from repeated eruptions

Pyroclastic flow

A cloud of extremely hot ash, gas and steam that rolls down the side of the volcano