The distribution of planet boundaries and the operation of these processes

Tectonic distribution

• earthquakes Are not random

• They are often found in clusters along plate boundaries

• 95% of earthquakes occur at plate boundaries

• 70% on the ring of fire

• Most powerful or associated with conservative or destructive boundaries

• Intraplate earthquakes can occur (Rarely)

Tectonic distribution volcanoes

• associated with plate boundaries

• Intraplate formations can a occur called hotspots - Hawaii

• No Volcanoes on conservative boundaries

• Most violent are found on destructive boundaries

• Constructive plate boundaries create effusive volcanoes

Oceanic– Continental Destructive plate boundary

• convection cell moves, oceanic plate and subduct

• An oceanic trench is formed where two plates meet

• The friction of the plates causes earthquakes (Benioff zone) as the ocean plate moves downwards, it melts creating magma. This rises and breaks through the surface to farm steep sided composite volcanoes.

• Thick Sticky lava creates steep sided or composite volcanoes that can be very explosive

• Continental plates are buckled by the collision of the plate causing fold mountains

• EG. NAZCA. Below

Oceanic – oceanic Destructive Plate boundary

• two oceanic plates moved together and the denser/faster one is subducted under the other

• This forms Deep ocean trenches

• The plate melts and the magma rises and forms underwater volcanoes

• Eventually, the underwater volcanoes will rise above sea level and farm island arcs

• Earthquakes are produced with shallow/deep focus which can be very powerful

  E.g. Japanese islands

Continental – Continental destructive Plate boundaries

• sometimes called a collision margin

• As both plates are similar densities and less dense than the asthenosphere neither subduct

• As they collide the sediments between them are crumpled up and eventually form Highfold mountains

• Volcanic activity as the plates are not subducted

• There are earthquakes which are often shallow and are more severe

  E.g. the Himalayas

Oceanic – oceanic constructive plate boundary

• convection currents pull these two oceanic plates apart

• a fissure is created between the two plates and passes easily through to form shield volcanoes

• The magma breaks through the crust it creates low frequency earthquakes

• On land rift valleys are formed. The crust stretches and breaks into sets of cracks called transform fault.The land between these faults collapse forming steep valleys called rift valleys

• The magma is very runny and will form more of the shield volcanoes overtimE

  E.g. mid Atlantic Ridge

Continental – Continental conservative margin

• as the play slide past each other, it is not smooth

• The plates grind past each each other the plates get stuck and the pressure builds

• Pressure finally releases and the plate slip past in a sudden movement. The shock waves can cause an earthquake

• Crust isn’t created or destroyed there are no volcanoes but earthquakes can be violent

E.g. San Andreas Fault California