Plate Tectonics and Hazard Effects

Plate Tectonics

A theory stating that the earth's surface is broken into plates that move.

Plate Margins

The place where tectonic plates meet and the earth is particularly unstable

Crust

The thin and solid outermost layer of the Earth above the mantle

Mantle

The largest layer of the earth between the crust and the core which is made up of semi-molten rock which is constantly moved by convection currents.

Outer Core

A layer of molten iron and nickel that surrounds the inner core of Earth

Inner Core

A dense sphere of solid iron and nickel at the center of Earth

Convection Current

A circular current of molten magma in the mantle caused due to the difference in temperatures within the mantle.

Magma

Molten rock beneath the earth's surface

Lava

Magma that reaches Earth's surface

Constructive Plate Margin

A plate margin where two plates are moving apart

Destructive Plate Margin

A plate margin where two plates are moving towards each other resulting in one denser plate sinking beneath the other.

Collision Plate Margin

Two continental plates collide. Neither plate is forced under the other, and so both are forced up and form fold mountains

Conservative Plate Margin

Tectonic plate margin where two tectonic plates slide past each other.

Continental Crust

The relatively thick but less dense part of the earth's crust that forms the large landmasses. It is generally older and more complex than the oceanic crust.

Oceanic Crust

Thinner, more dense, younger crust making ocean floor

Subduction Zone

In tectonic plates, the site at which an oceanic plate is sliding under a continental plate.

Primary effects

The initial impact of a natural event on people and property, caused directly by it.

Secondary effects

The indirect effects of a natural event.

Lava flows

Molten rock that flows over the ground

Pyroclastic flows

Scalding avalanche of ash and hot, toxic expanding gas, traveling very fast down the flank of a volcano

Ash fall

The deposition of a layer of fine airborne rock and glass that have been erupted from a volcano

Gas (steam)

Toxic fumes and superheated water emitted from a volcano before and during an eruption

Acid Rain

Rain containing nitric and sulfuric acids

Shaking ground

During energy release, seismic waves vibrate solid ground

Liquefaction

The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud

Tsunami

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

Fire

A hazard triggered when broken gas pipes are ignited by electricity sparks, or when gas stoves are toppled over.

Lahars

A destructive mudflow on the slopes of a volcano.

Infrastructure collapse

Seismic shockwaves cause buildings to twist and vibrate which can lead to them falling down, including bridges, roads, ports and railways

Casualties and deaths

Impact on people who are injured or fatally wounded due to building collapse, fire, tsunami etc