Cerro Azul's April 1932 eruption was one of the largest of the 20th century. Releasing of lava, the volcano ejected primarily dacitic tephra, accompanied by rhyodacite, andesite, and minuscule amounts of andesitic and basaltic scoria. At least one eruptive period lasted for 18 hours, creating an exceptionally uniform deposit. Eruption columns, extending into the air, were sighted. Phenocrysts were similar to the effusive eruption in 1846. Soon after, both the Tinguiririca and Descabezado Grande volcanoes began erupting, sending clouds of ash into Argentina. The eruption had a Volcanic Explosivity Index (VEI) of at least 5.