Rhyolite Structure in Southern Andes
April 15, 2016
Photographer: Eduardo Julia
Summary Author: Eduardo Julia
Shown above is a rhyolite structure in the southern Andes Mountains of Argentina, bordering Viedma Lake. Rhyolite is a silica-rich volcanic rock, similar in composition to granite. However, because it cools quickly, unlike granite, its crystals grow quickly, so rhyolite is fine grained and generally uniform in color. Due to its high silica content rhyolite lavas are highly viscous and often result in rounded formations after hardening. In this case, the colors come from superficial mineral oxides (mostly iron and magnesium). Photo taken on March 3, 2016.