1. The 3 main types of plate boundaries/margins

2. Divergent or constructive margins
4-A mid-ocean ridge is formed by the new crust.
6-Earthquakes are caused by volcanic eruptions or by tensional forces.
5-Submarine volcanoes appear along the ridge. Some may grow to form islands, e.g. Iceland.
Oceanic crust
Oceanic crust
1-Convection currents pull plates apart.
2-This leads to gaps being formed in the crustal rocks.
3-As the plates move apart, magma from the mantle rises to fill the gaps and forms new oceanic crust.

4. Destructive/convergent margins: Ocean-to-continent margin
7-The collision causes
folding and uplift of
rocks which form fold
mountains.
6-The Peru-Chile trench
forms where the
oceanic plate is being
subducted.
5-The melting plate
creates lighter
magma that rises
towards the surface
to form volcanoes.
1-The Nazca Plate and the South American Plate move towards each other due to convection currents.
Andes fold mountains
Pacific
Ocean
Trench
Volcano
Nazca Plate
(Oceanic)
South American
Plate (Continental)
Mantle
Earthquakes
Subduction
zone
4-The heat from
the mantle causes
the oceanic plate
to be destroyed.
2-The Nazca Plate (oceanic) is being subducted below the South American Plate (continental).
3-Friction and pressure
cause earthquakes to
occur along the subduction zone

6. Destructive/convergent margin b- Continental-to-continental margin
2- This results in intense folding and uplift and leads to the formation of fold mountains.
4- However, earthquakes occur due to the collision of the plates.
1- When two continental plates meet at a destructive boundary, a slow collision takes place as both plates have a low density.
3- There is no subduction. Therefore, there are no volcanoes.

8. Conservative [transform] margins
Plates just slide past each other with crust neither created nor destroyed.
Friction builds up and energy is released when the plates ‘jerk’, causing earthquakes.
The San Andreas Fault in California marks the junction of the North American and Pacific plates. Both plates are moving north-west but at different speeds. Instead of slipping smoothly past each other, they tend to ‘stick’. The pressure builds up until suddenly the plates move forward and an earthquake occurs.
There is no volcanic action because the crust is not being destroyed.