GEOLOGY

Detailed explanation-1: -A volcano erupts quietly if its magma is low in silica. Low-silica magma is thin and runny and flows easily. The gases in the magma bubble out gently. Low-silica lava oozes quietly from the vent and can flow for many kilometers.

Detailed explanation-2: -Basaltic Lava Magma that has a lower viscosity and lower silica content produces the volcanic rock called basalt and forms shield volcanoes.

Detailed explanation-3: -MAGMA COMPOSITION AND ROCK TYPES The magma types vary from mafic magmas, which have relatively low silica and high Fe and Mg contents, to felsic magmas, which have relatively high silica and low Fe and Mg contents.

Detailed explanation-4: -Volcanoes that have very hot, low-silica magma generally erupt quietly. In a quiet eruption, lava erupts in a stream of low-viscosity lava, called a lava flow.

Detailed explanation-5: -In a widely accepted silica-content classification scheme, rocks with more than 65 percent silica are called felsic; those with between 55 and 65 percent silica are intermediate; those with between 45 and 55 percent silica are mafic; and those with less than 45 percent are ultramafic.