Why do volcanoes produce different types of lava viz ;basaltic lava, rhyolithic lava and andesitic lava ?

Anonymous

Dear reader,

Volcanic products can be classified by their chemistry. This is handy when crystals are absent or to small to see with the naked eye. Since silica (silicon and oxygen) is the major component in rocks it is used for classification. Here's the classification:

basalt: 48-52 weight percent silica
basaltic andesite: 52-56 weight percent silica
andesite: 56-64 weight percent silica
dacite: 64-68 weight percent silica
rhyolite: >68 weight percent silica

Have a look at Minerals, Magmas, and Volcanic Rocks.

Steve Mattox, University of North Dakota

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