Restless Earth Flashcards
Crust
The outer layer of the earth
Plate
A section of the earth’s crust
Mantle
The dense, mostly solid layer between the outer core and the crust
Convection currents
The circular currents of heat in the mantle
Inner core
The centre and hottest part of the Earth. Its solid and made up of iron and nickel. Temperatures up to 5500°C.
Outer core
Surrounds the inner core. A liquid layer, also made up of iron and nickel.
Oceanic crust
Newer, most less than 200 million years old. Denser than continental crust.Can be subducted (sink). Can be renewed and destroyed.
Continental crust
Older, most over 1500 million years old. Less dense than oceanic crust. Cannot be subducted (sink). Cannot be renewed and destroyed
Plate margins
The boundary where two plates meet
Subduction
When a oceanic plate sinks below a continental plate.
Destructive - Subduction
Oceanic plate moves into and subducts beneath continental plate. E.g. Juan de Fuca Plate (oceanic) subducts beneath North American Plate (continental)
Destructive – collision
Two continental plates move together to form fold mountains. E.g. Indo-Australian Plate (continental) collides with the Eurasian Plate (continental) to form the Himalayas
Constructive
Two plates move away from one another. If two oceanic plates move apart shield volcanoes form to create islands. E.g. North American Plate and the Eurasian Plate move away to form the Mid-Atlantic ridge and Iceland.
Conservative
Two plates slide past one another, getting locked together and often jolting past each other to form earthquakes. Volcanoes do not form at this margin. E.g. North American Plate and the Pacific Plate create the San Andreas Fault – a conservative fault line under San Francisco.
Young fold mountains
Large mountain ranges where rock layers have been crumpled and forced upwards as they have been forced together at destructive margins.
