Chimpa has two summits, the {{convert|4856|m}} high Cerro Chimpa and the {{convert|4796|m}} high Cerro Cajón. The volcanic edifice was constructed in two stages, the first consisting of explosive and the second of effusive activity. The explosive activity generated ignimbrites and pyroclastic flows. On top of these, many poorly preserved lava flows were emplaced in a radial pattern and constitute three separate formations.^[1]

The volcanic rocks are of basaltic andesite to andesite composition, defining a potassium-rich calc-alkaline suite. They contain phenocrysts of biotite, hornblende, ilmenite, magnetite, orthopyroxene, plagioclase and quartz. Mafic inclusions occur in some eruption products.^[1]

The basement of the region is formed by various formations of Precambrian to Tertiary age, some of which crop out around the volcano. This basement is cut by various faults, which mark an uplift that forms the Creston Alto de La Aguada east of Chimpa volcano, as well as the Calama-Olacapato-El Toro lineament and associated faults which runs south of the Chimpa volcano and has localized the formation of volcanoes along its path^[1] and also influenced the activity of Chimpa. Cerro Rumio is another volcano which crops out south of Chimpa and is in part buried by Chimpa's deposits.^[1]

References