Chufquen, Chile

The picture shows Volcan Chufquen, a monogenetic scoria cone which formed
700 years ago on the side of Volcan Sollipulli. Scoria is vesicular
basalt, formed by explosive eruption. The red color is caused by oxidation
of iron (like rust) in the scoria, which may have happened because of
rainfall during the eruption. Cones like this are very common close to
large stratovolcanoes.
Other Images in the Sollipulli area:
Information Source: Mike Murphy, Univeristy of Bristol