Plate Tectonics - Glossary

Acidic Lava	Thick slow moving lava.
Basic Lava	Runny fast flowing lava.
Collision Margin	Where two continental plates meet forming fold mountains.
Composite Volcano	Occurs when the lava is acidic and it builds up to form a cone. Found at destructive boundaries.
Conservative Margin	These are where two plates are moving past each other causing friction. Eg: San Andreas Fault.
Constructive Margin	Plates that are moving apart which allows mantle to rise to the surface creating new crust. (Divergent)
Continental Crust	Between 25 and 100 km. thick. But lighter than oceanic crust.
Convection Current	Circular movement of mantle caused by heat.
Crust	Hard outer shell divided into plates.
Destructive Margin	Where oceanic and continental plates move together and the oceanic plate sinks under the other.
Divergent	Plates that are moving apart which allows mantle to rise to the surface creating new crust. (Constructive Margin)
Earthquake	Caused by the friction of plates.
Epicentre	The point on the surface straight above the focus.
Fissure	Crack in the ground or seabed which allows mantle to rise.
Focus	Its the centre of the Earthquake, often underground.
Fold Mountain	Are formed by the pushing up of continental plates creating mountains eg: Himalayas. Created at zones of subduction and where two continental plates meet.
Hot spots	Where volcanoes occur away from plate margins, probably due to strong upward currents in the mantle.
Inner Core	Solid center of the Earth. Very hot up to 5.500ºC.
Lahar	A mudflow caused by the melting of snow or a crater lake mixed with volcanic ash. Very fast and very dangerous.
Magnitude	The ammount of energy an Earthquake has.
Mantle	Soft molten rock about 3.800ºC surrounding the outer core.
Oceanic Crust	Made of basalt under the ocean, 5 to 10 km. thick. Very dense and sinks under continental crust when they meet.
Outer Core	This is liquid iron and nickel surrounding the inner core
Plate Boundary	Place where 2 plates meet.
Plug	Solidified lava blocking a volcano's vent
Pyroclastic flow	A mixture of gas, steam and ash which flows quickly down the side of the mountain in the form of a cloud.
Recurrence interval	The ammount of time between earthquakes of similar magnitude.
Richter Scale	The scale used to measure earthquakes' magnitude.
Seismologist	Scientists who study earthquakes.
Seismometer	Instrument used to measure movement underground.
Shield Volcano	Occurs when the lava is basic, forming a flat volcano. Found at constructive boundaries.
Subduction	Oceanic plates sinking under continental plates.