Toconce volcano has a central crater and is constructed mainly by andesitic lava flows, which were emplaced during three different stages. The last stage generated the bulk of the volcanic edifice. The volcano was glaciated between 15,000 - 11,000 years ago and this has resulted in glacial erosion and the development of moraines above elevation. The glacial erosion has excavated a number of glacial valleys on the volcano, and hydrothermally altered rocks from inside the edifice have been exposed.