constructive

• Where convection currents move plates apart, constructive plate boundaries (margins) are formed.

  The Earth's crust is pulled apart to create a new pathway for rising hot magma from the mantle to flow on to the surface to make a new crust . Volcanoes can sometimes form in these settings; one example is Iceland .When this happens the magma from the mantle rises up to make new land in the form of a shield volcano. The movement of the plates over the mantle can cause earthquakes.