Explain and describe the formation of constructive plate boundaries and a landform associated with them.

A constructive plate boundary occurs when two tectonic plates are moving away from one and other. This movement is caused by currents within the mantle. As the plates are slowly pulled apart the rising magma in the mantle pushes its way to the surface. The magma that rises as the plates diverge causes volcanic eruptions. However, unlike at destructive plate boundaries where eruptions can be short and violent, at constructive plate boundaries eruptions are typically prolonged and less explosive. These slow eruptions of thin basaltic lava lead to the formation of volcanoes with wide and gently sloping sides known as shield volcanoes. They gain their sloped sides due to the low viscosity of the basaltic lava and the prolonged duration of the eruption.