Option G - Hazardous environments

Hazard

A potentially damaging natural event that poses a threat to people, property, or the environment

Disaster

When a hazard actually causes significant harm

Risk

The likelihood of a hazard causing harm, influenced by exposure, vulnerability and capacity to respond

Vulnerability

How susceptible people or places are to harm from a hazard

Convergent (destructive) boundary

Plates move toward each other, oceanic plate subducts beneath continental plate

Divergent (constructive) boundary

Plates move away from each other, magma rises to form new crust

Transform (conservative) boundary

Plates slide past each other, no crust is created or destroyed

Convection cells

Heat from the Earth’s core causes hot magma to rise and cooler magma to sink into the mantle

Ridge push

A divergent (constructive) boundary, magma rises to form new crust (e.g. mid-ocean ridges), as magma cools and hardens, it forms elevated ridges, gravity causes the new crust to slide down the slop, pushing plates apart

Slab pull

At convergent (destructive) boundary, a denser oceanic plate subducts underneath a lighter plate, as the oceanic plate sinks into the mantle, it pulls the rest of the plate with it

Soil creep

The micro-movement of individual soil particles downslope

Shield volcano

A broad, gently sloping volcano formed by low viscosity, basaltic lava that flows easily and spreads over large areas

Composite volcano (stratovolcano)

A steep, cone-shaped volcano made of alternating layers of lava, ash, volcanic rock which eruptions are explosive and dangerous

Lava

Molten rock that erupts onto the Earth’s surface from a volcano

Pyroclastic flow

A fast-moving, deadly cloud of hot gas, ash, and volcanic rock that races down the side of a volcano during an explosive eruption

Lahar

A volcanic mudflow made of ash, rock, and water, often triggered by rainfall or melting ice on a volcano

Epicenter

The point on the Earth’s surface directly above the focus of an earthquake

P-wave

A type of seismic wave that compresses and expands the ground that is fast and shakes the ground in the direction they travel

S-wave

A seismic wave that moves the ground up and down or side to side, slower

Love waves

A type of surface seismic wave that moves the ground side to side horizontally, causing intense shaking and damage

Rayleigh waves

A type of surface seismic wave that move the ground in a rolling, elliptical motion, similar to ocean waves

Liquefaction

The process by which an earthquake’s violent movement makes soil lose its structural integrity