Geography Year 9 - 1. Hazards

List of key terms for the first module - Hazards

Geothermal

relating to or produced by the internal heat of the earth.

Fold mountains

are mountains that form mainly by the effects of folding on layers within the upper part of the Earth's crust.

Secondary effects

the knock on effects of a hazard which result from the primary effects

Shield volcano

Type of volcano found at constructive plate boundaries which are low with gently sloping sides

Composite volcano

Type of volcano normally found at destructive plate boundaries. Made up of layers of lava and ash

Tephra

rock fragments and particles ejected by a volcanic eruption

Lava

hot molten rock erupted from a volcano

Magma

molten material below the earth's crust

Pyroclastic flow

a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing at great speed.

Seismometers

A machine used to measure the magnitude of an earthquake

Richter scale

A scale used to rate the magnitude of an earthquake - the amount of energy it released.

Primary effects

The initial impact of the hazard

Focus

the place in the Earth's crust where the earthquake starts

Epicentre

directly above the focus on the earth's surface

Crust

the layer that we live on. It is a thin skin of rock around the earth, like the skin on an apple

Mantle

The layer underneath the crust. It is molten and can reach temperatures of up to 5000°C.

Core

Found at the centre of the Earth. Mainly made up of iron with a little nickel

Tectonic Plate

The crust of the earth is divided into a small number of these which float on and travel independently over the mantle

Subduction

the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.

Convection current

Currents in the crust which are responsible for plate movement

Constructive plate boundary

when tectonic plates move apart

Destructive plate boundary

This occurs when oceanic and continental plates move together. The oceanic plate is forced under the lighter continental plate

Collision plate boundary

when two continental plates collide

Conservative plate boundary

occurs where plates slide past each other in opposite directions, or in the same direction but at different speeds.

Natural hazard

a natural event with the potential to harm people and their property

Natural disaster

the realisation and impacts of a natural hazard i.e. the deaths, injuries, disruption and damage.