volcanoes and earthquakes

volcano

an opening in the Earth’s crust through which magma, molten rock and ash erupt

crater

depression at the top of a volcano after an eruption

lava

molten magma that has reached the Earth’s surface

shield volcano

gently sloping volcano made by runny basaltic lava; found at constructive boundaries and hotspots

magma

molten rock beneath the Earth’s surface

composite volcano

formed from alternating layers of ash and lava

volcanic ash

tiny particles of crushed volcanic rock and glass

magma chamber

reservoir of magma deep inside a volcano

pyroclastic flow

superhot flows of ash, rock and gas moving at very high speeds

vent

channel through which volcanic material is ejected

dormant

volcano not erupted for a long time but may erupt again

active

volcano that has erupted in recent times

extinct volcano

volcano not expected to erupt again

Richter scale / moment magnitude scale

measures earthquake magnitude (each step is 10× stronger)

Shindo scale

measures how strong an earthquake feels at a location

epicentre

point on the Earth’s surface above the focus

focus

point inside the Earth where an earthquake starts

earthquake

sudden shaking of the Earth after pressure is released

volcanic explosive index (VEI)

measures how powerful a volcanic eruption is

supervolcano

volcano with a VEI of 8

natural hazard

natural event that causes damage, disruption or loss of life

tsunami

large waves caused by sudden movement of water, usually by earthquakes

constructive / divergent boundary

plates move apart, new crust forms, volcanoes common

convergent / destructive boundary (subduction)

oceanic plate sinks under continental plate, volcanoes and fold mountains form

conservative boundary

plates slide past each other; no crust created or destroyed

inner core

solid, extremely hot centre of the Earth

outer core

semi

mantle

thick semi

crust

solid outer layer of the Earth, oceanic and continental

major plate boundaries

Pacific, Indo

convection currents

hot material rises and cool material sinks, moving plates

magnitude

energy released by an earthquake

tremor

small earthquake

regulations

rules, e.g. for safe building in earthquake areas

casualties

people killed or injured

seismic wave

vibrations that carry earthquake energy through Earth

shock wave

another word for seismic wave

concentric pattern

circles within circles

classify

group into types