Details about another large explosion on 17 July that sent a plume to over 10 km altitude will be reported in a future issue. Prior to that, during the month of June, degassing and explosions continued. The highest level of activity in 13 days was recorded on 1 June, but by 4 June activity had dropped to the lowest level in a month and it remained low through the end of June. Accordingly, during June explosions and degassing events became less frequent, shorter in duration, and of lower intensity. On 5 July one of two explosions sent an ash column to ~2,500 m and produced ashfall 10-20 km W of the summit.

A 3 June aerial inspection verified that no new summit crater has been formed, but did record a recent increase in the size of the crater formed during the 10 February and 10 May explosions. The crater diameter is now 180-200 m, with the deepest sector measuring 70 m.

Early in June authorities continued the evacuation of La Yerbabuena, in the state of Colima, and Juan Barragán, Los Machos, El Borbollón, and Durazno, in the state of Jalisco. The Observatory recommended controlled access to areas within 8.5 km of the summit and alert to persons within 11.5 km. People in other high-risk areas were told to be prepared to evacuate. By 10 June, however, reduced activity enabled authorities to relax restrictions. They trimmed the evacuated zone to within 6.5 km of the summit and maintained immediate response capacity to 8.5 km (including the villages of La Yerbabuena, Juan Barragán, El Agostadero, Los Machos, Borbollón, and El Durazno). Radio alert was maintained to a 11.5 km radius of the summit (encompassing the settlements of Causentla, Cofradía de Tonila, Atenguillo, Saucillo, El Fresnal, El Embudo). Authorities allowed residents to return to evacuated communities in both Colima and Jalisco. On 2 July, due to recent rain and the potential for lahars, authorities recommended avoiding the bed of the Cordobán river.

Geological Summary. The Colima complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the high point of the complex) on the north and the historically active Volcán de Colima at the south. A group of late-Pleistocene cinder cones is located on the floor of the Colima graben west and east of the complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide scarp, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, producing thick debris-avalanche deposits on three sides of the complex. Frequent recorded eruptions date back to the 16th century. Occasional major explosive eruptions have destroyed the summit (most recently in 1913) and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: Colima Volcano Observatory, University of Colima, Ave. 25 de Julio 965, Colima 28045 México (URL: https://portal.ucol.mx/cueiv/).