As of 10 October, volcanic activity at Colima consisted of an average of two explosions per day producing ash clouds that rose to ~2 km above the crater and drifted predominately W. On 7 October rain from Tropical Storm Olaf inundated the Colima area with 150 mm of rain in less than 2 hours. The heavy rain mixed with material on the volcano's S flank, producing a lahar down the Montegrande ravine. According to the Washington VAAC, on 9 and 10 October ash clouds were visible on satellite imagery rising to a maximum height of ~5 km above the volcano.

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.

Sources: Centro Universitario de Estudios e Investigaciones de Vulcanologia - Universidad de Colima, Washington Volcanic Ash Advisory Center (VAAC)