SERNAGEOMIN reported that during the last two months activity at Láscar had declined to low levels, based on seismological, geodetic, geochemical, and remote sensing data, though remained above baseline. The volume of the lava dome remained unchanged, seismicity was low including small numbers of volcano-tectonic and tornillo-type events, sulfur dioxide gas emissions were low, and tephra was absent from emissions. On 6 April the Alert Level was lowered to Yellow (the second lowest level on a four-color scale) and the public was warned to stay at least 5 km away from the crater. SENAPRED updated the Alert Level Yellow (the middle level on a three-color scale) for San Pedro de Atacama (70 km NW) and maintained a security perimeter of 10 km around the volcano.

Geological Summary. Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED)