A group from CICBAS (Universidad de Colima) and CONMAR (Oregon State Univ) visited the volcano 15-17 February. Since their last visit, in May 1989, rockfall avalanches have occurred preferentially on the SW flank. Fumarolic activity persisted throughout their visit, forming a dense gray cloud. Poor weather conditions limited additional observations.

The geologists emplaced geoceivers for satellite communication, to determine geodetic positions of sites near the volcano for installation of two new telemetering seismographs. On 15 December 1989, the CICBAS seismology group had installed the 4th telemetric station of the Red Sismológica Telemétrica de Colima, 7 km from the volcano (at la Yerbabuena, site EZV6 on figure 6).

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: Guillermo Castellanos, Gilberto Ornelas-Arciniega, C. Ariel Ramírez-Vazquez, G.A. Reyes-Dávila, and Hector Tamez, CICBAS, Universidad de Colima.