Toconce volcano has a central crater and is constructed mainly by andesitic lava flows, which were emplaced during three different stages.

The volcano was glaciated between 15,000 - 11,000 years ago and this has resulted in glacial erosion and the development of moraines above 4,300 metres (14,100 ft) elevation.

[4] The relatively small Tolar ignimbrite was erupted from Toconce volcano, over 1.3 million years ago.

[6] The rocks at Toconce are formed primarily by plagioclase and glass, with amphibole, biotite, pyroxene and quartz making up the rest.

Hydrothermal alteration has given rise to clay, oxidation products and sericite.