reaching distances of from the vents. Winds blew ash from the pyroclastic flows, and rain eroded freshly deposited pyroclastic deposits. Ash fall and pyroclastic flows alternated during this stage, probably caused by brief obstructions of the vent; at this time a lava dome formed within the second vent. A change in the composition of the erupted rocks occurred, the "Dacite 1" geochemical suite being increasingly modified by the "Dacite 2" geochemical suite that became dominant during the third stage. Pyroclastic flows ran down the slopes of the volcano, entered the Río Tambo valley and formed dams on the river, probably mainly at the mouth of the Quebrada Aguas Blancas; one of the two dammed lakes was about long. When the dams failed, the lakes released hot water with floating pumice and debris down the Río Tambo. The deposits permanently altered the course of the river. The volume of the ignimbrites has been estimated to be about , excluding the ash that was erupted during this stage. The pyroclastic flows along with pumice falls covered an area of about . In the third stage, Vulcanian eruptions took place at Huaynaputina and deposited another ash layer; it is thinner than the layer produced by the first stage eruption and appears to be partly of phreatomagmatic origin. During this stage the volcano also emitted lava bombs; the total volume of erupted tephra is about . This third stage destroyed the lava dome and formed the third vent, which then began to settle along the faults as the underlying magma was exhausted. The fourth vent formed late during the eruption, outside of the amphitheatre. Witness observations The eruption was accompanied by intense earthquakes, deafening explosions and noises that could be heard beyond Lima and as far away as . In Arequipa, the sky was illuminated by lightning, and ash fell so thick that houses collapsed. The noise of the eruption was perceived as resembling artillery fire. There and in Copacabana the sky became dark. The blasts of the eruption could be heard (anecdotally) as far as Argentina and in the coastal localities of Lima, Chiquiabo and Arica. In these coastal localities it was thought that the sound came from naval engagements, likely with English corsairs. In view of this, the Viceroy of Peru sent reinforcement troops to El Callao. Closer to the vents, inhabitants of the village of Puquina saw large tongues of fire