Types of plate Margin
Earthquakes and volcanoes occur at constructive margins
· Constructive margin = two plates are moving apart (diverging).
· Mantle under pressure from plates above. When moves apart, pressure released at margin.
· Release of pressure causes mantle to melt, producing magma.
· Magma less dense than plate above, so rises and can erupt to form a volcano.
· Plates don’t move in uniform way (some parts move faster than others – pressure builds up), when pressure becomes too much the plates cracks, creates fault line causing an earthquake. (Further earthquakes occur along fault line once it has been created).
· Constructive margins create two different landforms:
Ø Where diverging plates are underwater mid-ocean ridge forms
Ø E.g. Mid-Atlantic Ridge where Eurasian plate and North American plate are moving apart
Ø Underwater volcanoes erupt along mid-ocean ridges and can build up above sea level
Ø E.g. Iceland formed by build-up of underwater volcanoes along Mid-Atlantic Ridge
Ø Plates diverge beneath land, rising magma causes continental crust to bulge and fracture, forming fault lines
Ø As plates…