Shield volcanoes (lava volcanoes)
Shield volcanoes account for the majority of volcanoes (90%). They occur, for one, within tectonic plates (e.g. Hawaii Islands), and, for another, at divergence zones (e.g. Iceland). This type of volcano mainly occurs under the sea.
Shield volcanoes are characterised by a convex form resembling a shield, and are formed by the expulsion of highly molten lava. This form of eruption is referred to as effusive eruption. The escaping lava has a high proportion of potassium and a lesser proportion of silicic acid. The magma originates from the upper layers of the Earth's crust. The lava is highly molten and can attain a speed of 60 km/h. Since the gases can readily escape, eruptions are not explosive.