hazardous environments key terms

Natural disaster

Non-human/physical hazard event (e.g. an earthquake) that causes damage, destruction or death.

Earthquake

A sudden release of pressure releasing energy in the form of seismic waves which causes the ground to shake.

Risk equation

Risk = hazard x vulnerability / capacity to cope

Active volcano

An erupting volcano or one likely/capable of erupting/ejecting material at any time.

Hazard risk assessment

A hazard is an event that threatens to adversely affect human life and a risk assessment is deciding the probability of the hazard event occurring and affecting people

Wind shear

Wind speed and direction are different from normal over a short period of time. The speed of the wind changes with altitude.

Epicentre

The point on the earth's surface directly above the focus of an earthquake

Tectonic plate

Giant slabs of crust that make up the earth's surface

Risk assessment

The probability of a particular event happening and the scale of its possible damage

Upwelling

The upward movement of lava through a gap at a constructive plate boundary

VEI

Volcanic Explosivity Index

Tsunami

A giant wave usually caused by an earthquake beneath the ocean floor.

Richter scale

A scale that rates an earthquake's magnitude based on the size of its seismic waves.

Moment magnitude scale

A scale that rates earthquakes by estimating the total energy released by an earthquake

Mercalli scale

A scale that rates earthquakes according to their intensity and how much damage they cause at a particular place

Saffir-Simpson Scale

Classifies hurricanes according to wind speed, air pressure in the center, and potential for property damage.

Coriolis Force

The apparent force, resulting from the rotation of the Earth, that deflects air or water movement.

Northern hemisphere rotation

Clockwise

Southern hemisphere rotation

Anti-clockwise

Dormant volcano

A volcano that has not erupted for a long time, but may erupt again one day.

Extinct volcano

A volcano that has not erupted for thousands of years and will not erupt again.

The tropics

The area between the Tropic of Cancer and the Tropic of Capricorn

shield volcano

forms at constructive boundaries, lava flow is not explosive or viscous, gentle sloped sides, no layers, more frequent eruptions

composite volcano

destructive boundaries, pyroclastic flow is explosive and viscous, steep sides, layers of lava and ash, less frequent eruptions

seismic wave

the vibrations from earthquakes that travel through the earth.

subduction zone

the area where two tectonic plates overlap in the mantle and the oceanic plate is denser so is forced beneath the lighter continental plate.

plate margin

the point where two plates meet. earthquakes and volcanoes are most likely to occur here

tropical storms

hurricane, cyclone, typhoon

storm surge

increased height and sea level caused by difference in pressure between storm and eye.

eye

clear and calm conditions, centre of low pressure

fault

a break in the earth crust along which movement occurs

after shock

an earthquake following the main earthquake

seismometer

seismometers record the ground motion from an earthquake

collision

two continental plates collide, neither can sink. as they are pushed together material is forced up creating huge mountain ranges. the pressure can cause earthquakes.

conservative

plates move past eachother building up friction until the plates become stuck. pressure builds up until the energy is released which causes an earthquake close to the surface.

destructive

an oceanic and continental plate move together. the denser oceanic plate subducts and it partially melts and it forced up through a compositve volcano

constructive

plates move apart from eachother leaving space for magma to rise up and form new land in the form of a sheild volcano.

primary effects

effects that are directly caused by the physical event. eg. damage from high winds, flooding, storm surges and people killed during the storm.

secondary effects

follow on from first effects and include; long term homelessness, water pollution, loss of jobs, insurance costs, government costs and water foods shortages.

convection current

heat rising and falling inside the mantle creates currents. the magma closer to the centre of the earth is heated and rises and as it rided it cools and sinks in a circular current.

lahars

if the ash and mud from a volcanic eruption mix with rain water or melting snow, it creates fast moving mud flows.

volcanic ash

a mixture of rock, mineral and glass particles expelled from a volano

pyroclastic flows

a fast moving current of hot gas and volcanic matter. moves away from the volcano at 100km/h. with temp over 400C

lava flows

thin slow moving runny lava. more gentle eruptions