Dacite lava is a viscous lava which is squeezed out of volcanoes and commonly forms lava domes. If this collapses then pyroclastic flows can occur. It erupts at a temperature between 800 and 1000 C.If the magma is gaseous then Plinian style eruptions can occur when low in gases dacite is extruded as a lava dome.
It forms a light grey rock which contains 63% to 68% silica and the minerals plagioclase, pyroxene and amphibole / hornblende. Dacite is found above subduction zones particularly on ocean/continent boundaries. Mt.St Helens.Mt Pinatubo and Mt.Unzen have all erupted Dacite.