This eruption was the most significant eruption of Lascar in the last 9,000 years , with a volcanic explosivity index of 4 and a duration of 32 hours . It caused noticeable changes in the morphology of the volcano , including the formation of a new fracture along the summit craters ; however , the summit craters themselves were not heavily altered apart from the formation of a trench across the three craters that runs in west – east direction . The whole volcano did not deform during the eruption sequence . The eruption released about of sulfur dioxide , about half the quantity released by the 1980 eruption of Mount St. Helens , and was sufficient to cause a noticeable increase in atmospheric opacity . The Quebrada Tumbre was blocked , and its water chemistry noticeably altered , by the eruption . About of gypsum was deposited in the drainages around the volcano , forming a significant supply of sulfur in the region
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
Lascar (volcano)