Edexcel a level geography -Tectonics key terms

Mantle

Is a solid but because of high temperatures present it is locally deformable (plastic) and capable of very slow ‘flow’.

Mantle plumes

Are concentrated areas of heat convection. At plate boundaries they are sheet-like, whereas at hot spots they are column-like.

Subduction

Is the process of one plate sinking beneath another at a convergent (destructive) plate boundary.

Focus

Where an earthquake originates from.

Epicentre

Is the point on the Earth’s surface directly above the focus.

Pyroclasts

Are any rock fragments ejected from a volcano, including ash, tephra and volcanic bombs.

Threshold

Is the magnitude above which a disaster occurs. This threshold level could be different in a developed vs developing country because of the different levels of resilience.

Resilience

Is the ability of a community to cope with a hazard; some communities are better prepared than others so a hazard is less likely to become a disaster.

Mega-disaster

Is a disaster with unusually high impacts. Today that means millions of people are affected and billions of dollars in damage over a wide area E.g. an entire region/ even more than one country.

Liquefaction

Occurs in waterlogged, loose sediment; earthquake shaking ‘liquefies’ the ground, causing buildings to tilt, sink and collapse.

Supervolcano

Is one whose impacts would be felt globally, because of a worldwide cooling of the Earth’s climate, perhaps for up to 5 years.

Aftershocks

Occur in the hours, days and months after a primary earthquake and can be of high magnitude; they often number in the hundreds or thousands.

Corruption

Refers to illegal practices, such as accepting bribes designed to influence decision making/ paying people to stay silent about known problems.

Land-use zoning

Is a planning tool used to decide what type of buildings (residential, commercial, industrial or none) are allowed in particular locations.

Multiple hazard zones

Are places where two/ more natural hazards occur, and in some cases can interact to produce complex disasters.

Prediction

Means knowing when, and where, a natural hazard will strike on a spatial and temporal scale that can be acted on meaningfully in terms of evacuation.

Forecasting

Is much less precise than prediction. It provides a ‘percentage chance’ of a hazard occurring. E.g. 25% chance of a Mag 7.0 earthquake in the next 20 years.

Hazard resistant design

Involves constructing buildings and infrastructure that are strong enough to resist tectonic hazards. In the case of earthquakes these are called aseismic buildings.

Cry wolf syndrome

Occurs when predictions (and evacuation) prove to be wrong, so that people are less likely to believe the next prediction and waring and therefore fail to evacuate.

Earthquake kits

Are boxes of essential household supplies (water, food, battery-powered radio, blankets) kept in a safe place at home to be used in the days following an earthquake.