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A2 Geography Hazardous Earth > Features and processes > Flashcards

Flashcards in Features and processes Deck (11):

The global pattern of plates and plate boundaries

Since used for military purposed revealed invaluable data
Maps produced from seismic data showed that most earthquakes were concentrated around narrow bands


What are 3 types of plate boundary

Divergent (constructive)
Convergent (destructive)


Facts on Divergent boundaries

Plates are moving apart and magma is rising through the asthenosphere and forcing its way to the surface
Mainly occurs at MOR
Mountain chains


Transform faults

MOR are not continuous, they are broken into segments by transform faults
No volcanic activity
Earthquakes can occur


What are pillow lavas

Eruption of magma along divergent boundaries occurs mainly underwater
Magma erupting directly onto the sea bed is cooled rapidly forming rounded moulds called pillow lava's


What are black smokers

MOR sea water seeps into rifts and is superheated
Rises to the surface and causes chemical changes in the basaltic rocks
Superheated jets of water sometimes emerge containing metal sulphides


What are underwater rift valleys

Found along MOR
As magma rises to the surface the overlying rocks are forced up into a dome
Rigid lithosphere is placed under great stress and fractures along parallel faults


Oceanic - continental plate margins

Oceanic plates are denser so forced under continental plates when they converge
This is subduction
Forms a trench


Oceanic - Oceanic

The denser one will subduct
Creating a trench
Forms chain of volcanic islands


Continental - Continental

Little subduction occurs


Conservative plate margins

Slide past each other
No volcanic activity
Earthquakes can occur