Stratovolcano Stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive
Eastern Pilbara Craton of this region was dominated by volcanic activity, magmatic intrusion and deformation. The Eastern Pilbara Terrane is mostly volcanic in nature, and this volcanic activity occurred in relatively short, and repeated cycles These ultramafic-mafic-felsic cycles which last approximately 10–15 Myr each are accompanied by metamorphism/deformation, and followed by long pauses ( 75 myr) and clastic sediment deposition. Some of the granitic intrusions in the region are subvolcanic, which can be determined through the comparative chemical analysis of the intrusion and associated greenstones. All of these cycles are interpreted to be the result of successive mantle plume events. These events resulted