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
Geology of the Northwest Territories metavolcanic rocks. Quartz arenite in the Rae Craton has been interpreted as possible passive margin or rift deposits. Around the world, greenstone belts are a hallmark of ancient Precambrian rocks. The Ennadai-Rankin greenstone belt is the second largest in Canada and displays felsic volcanic and volcaniclastic rocks, as well as mafic rocks reaching greenschist grade on the sequence of metamorphic facies. Laminations in ironstone and pelite formations suggest that the mafic volcanic rocks deposited on the low energy slope of a volcanic plateau, away from wave action. Because of the enormous time distance from the Archean, exact interpretations are less