Asked in Volcanoes

Would you expect extrusive rocks produced by an explosive volcano to be light or dark in color?


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The color of igneous rocks is tied to their composition. Rocks (minerals) that have a high concentration of Fe, Mg and Ca, tend to be darker colored than those that are rich in Al, Si, and K. So, the volcanic rocks like rhyolite are light in color due to their composition. However, there are many volcanic rocks, like andesites, that are a bit darker, and those form from explosive volcanoes like the Cascade volcanoes of western North America.