Glossary

CDEM
Civil Defence and Emergency Management. The Ministry of CDEM leads the way in making New Zealand and its communities resilient to hazards and disasters.

civil defence
Steps taken by organised community groups for the protection of life and property in the event of a natural disaster.

continent
An enormous, unbroken area of land. Earth's surface is divided into Europe, Asia, Africa, North America, South America, Australia and Antarctica.

convection currents
Heat generated in the Earth’s core causes super-hot convection currents to circulate in the Earth’s mantle.

earthquake
A sudden movement of the Earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity.

epicentre
The point on the Earth's surface directly above the focus of an earthquake.

emergency plan
The steps to take to reduce risk to yourself, your family and your property in the event of a natural disaster.

fault
A break in rock across which there is observable movement.

hydrothermal activity
Hot springs, geysers and warm ground created by heat from nearby volcanic activity

lahar
A mixture of rock and ash from a volcanic eruption. It is like a mudflow that washes down the mountain, melting snow and flowing like a river.

landslide
Movement of soil, rock and debris down a slope.

liquefaction
A process in which water-saturated sediment temporarily loses its strength and acts as a fluid.

magma 
Molten rock beneath the Earth's surface.

magnitude
A measure of the energy released by an earthquake at its source. Magnitude is commonly determined from the shaking recorded on a seismograph. Each unit of magnitude on the scale represents a substantial increase in energy, for example a magnitude 6 releases 30 times more energy than a magnitude 5.

mantle
Area of the Earth between the core and the crust.

natural disaster
A natural event such as a flood, earthquake, or hurricane that causes great damage or loss of life.

plate boundaries
The edges of the plates that make up the crust of the Earth.

Plate tectonics
Plate tectonics is an explanation of how the surface of the Earth moves. 

subduction zone  
The area or zone where two tectonic plates come together, one riding over the other.

swarm
An earthquake swarm is a sequence of nearby earthquakes striking in a short period of time.

tectonic plates
Blocks of the Earth's continental and oceanic crust that move, float, and sometimes fracture. Their interaction causes continental drift, earthquakes, volcanoes, mountains, and oceanic trenches.

seismic waves
The waves of energy released by an earthquake.

tsunami
A series of powerful ocean surges caused by a large volume of the ocean floor being displaced – often by an undersea earthquake or landslide.

volcano
A volcano is a vent at the Earth's surface through which magma and volcanic gases erupt. It is also the cone built by effusive and phreatic eruptions.