 By 1932 , Quizapu had produced many phreatic events and one effusive eruption , but no large Plinian eruptions . This frequency of minor eruptive activity proved to be a precursor for a major eruption . On 25 January 1932 , observers in Malargue saw a large black cloud over the summit . By 9 April , the volcano emitted green gas and started to " bellow like a bull " . On April 10 , Cerro Azul finally erupted , releasing a towering column or plume of white gas . After 10 AM , the plume turned black with ash and began to form an umbrella shape . The ash was carried by wind into Puesto El Tristan in Argentina , about 47 kilometers ( 29 mi ) away , where beginning at 1 PM it rained down for hours . At 4 PM , coarser sandy material and some pumice lapilli began to fall . 
