Explosive eruptions and ash falls are the major threat to humans from Lascar. The frequent smaller explosive events commonly occur unexpectedly and can thus endanger people on the mountain. The towns of Tumbres and Talabre may be affected by pyroclastic flows, and ash falls can occur east of the volcano. Such ash falls could potentially hit the towns of San Pedro de Atacama, Talabre and Toconao as well as the Llano de Chajnantor Observatory, the San Pedro de Atacama-Paso de Jama-Jujuy international road and the Sico Pass. Past eruptions caused ash fall in Argentina and disruption of air travel and could have major effects in the Salta Province in case of renewed activity. In 1982, the town of Talabre was moved for safety reasons stemming from flooding and volcanic activity, and ballistic blocks ejected by the volcano are a threat to mountaineers and scientists working on Lascar. Sector collapse and lahars have occurred in the past, but are unlikely to be present-day hazards. The National Geology and Mining Service of Chile publishes a volcano alert level for Lascar.