<P> A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice, and volcanic ash . Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic explosive eruptions and effusive eruptions, although some have collapsed 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 felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi). </P> <P> Stratovolcanoes are sometimes called "composite volcanoes" because of their composite layered structure built up from sequential outpourings of eruptive materials . They are among the most common types of volcanoes, in contrast to the less common shield volcanoes . Two famous stratovolcanoes are Krakatoa, best known for its catastrophic eruption in 1883 and Vesuvius, famous for its destruction of the towns Pompeii and Herculaneum in 79 CE . Both eruptions claimed thousands of lives . In modern times, Mount Saint Helens and Mount Pinatubo have erupted catastrophically . </P>

What type of lava erupts from a composite volcano
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