The following report from James Luhr supplements the report from Mexican scientists in 07:01.

"The andesitic block lava that began to flow from the summit crater dome in early December was the first to descend Colima's S flank for hundreds of years. Geologists from the Univ. of California at Berkeley observed the flow from the S side of the volcano starting 18 January, about the time of the report in 7:1. The new lava was moving down a polished avalanche chute with a slope of about 36°. On 20 January, the flow had a simple tongue shape and was some 600 m long. By 3 March, the lava had reached 1 km length. Block-and-ash flows were common from the uppermost margins of the lobe with surprisingly few from the flow front. In several instances, sizeable (2,000 m² ?) areas on the flow surface suddenly shifted downslope 5-10 m, accompanied by only small amounts of ash and steam. This may be a major process of downslope movement of the flow. The active scree deposit below the lava contained blocks several meters in diameter, grading into a new sand and conglomerate wedge flooding the upper reaches of the Barranca Playa de Montegrande.

"Since the early part of Colima's lava eruption of 1975-76, through several episodes of dome growth, the andesitic magma has become progressively more basic. The latest lava continues this trend."

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: J. Luhr, Univ. of California, Berkeley.