Most activity at Sabancaya occurs in the form of lava domes and lava flows, one of which is dated to 5,440 ±40 years before present on the eastern flank. Additional surface exposure dating has yielded ages of 6,650 ±320 and 6,300 ±310 on various lava flows, indicating that effusive activity started shortly after the beginning of the Holocene although the basal part of the edifice did not exist yet at that time. Pyroclastic eruptions are less common and have a low volume, with one such occurrence dated to 8,500 years before present. This tephra layer, along with layers dated 2500-2100 BC, 420-150 BC, 100 BC - 150 AD and between 1200-1400 AD, could have originated either on Sabancaya or Ampato, however. There is evidence that early and middle-Holocene Sabancaya mostly erupted lava, while the late-Holocene volcano was more explosive in its activity. It is possible that the Inca performed human sacrifices in response to eruptions of Sabancaya to calm down the mountain spirits.