A major landslide occurred in the volcano's history during the late Pleistocene, probably triggered by volcanic activity. This landslide descended the eastern-southeastern flanks of the volcano into Argentina, first over a steep slope of 20° on the volcano, split around Cerro Rosado and entered the Salina de Llullaillaco east of the summit, extending up to into the salar. The toe of the avalanche reaches a thickness of above the salar in the avalanche's southern lobe. Part of the avalanche was channelled in a valley between Cerro Rosado and an unnamed volcano farther south. When it reached Cerro Rosado, the avalanche climbed about and mostly continued to flow southeast into the main avalanche path, with only a small flow continuing northeastwards. Part of the run-up avalanche later collapsed backwards over the main avalanche deposit. Unlike Socompa farther north, a landslide scar is only poorly developed at Llullaillaco despite the large size of the collapse; it was largely filled in later by lava flows and volcaniclastic debris.