MORPHOLOGICAL-CHANGES OF THE ACTIVE CONE OF GALERAS-VOLCANO, COLOMBIA, DURING THE LAST CENTURY

The morphology of the active cone of Galeras volcano is a consequence of the complex interplay between effusive and explosive processes, and erosion. The main crater, several secondary craters, and zones of fum arolic activity were formed on the active cone as a result of these pr ocesses. Analysis of detailed descriptions, from observations that beg an in 1989, indicates that volcanic activity led to the formation of m any fissures in the main crater and on the active cone which appear to show an important relationship with the volcano's structure. The frac tures and fissures are associated with a tangential system generally a ligned with the crater rim and a radial system that tends to intersect the crater rim at high angles. The intersections of the tangential an d radial systems have generated zones of weakness, some of which have developed into eruptive centers. Thus, certain fumaroles have evolved into small craters, and these craters have contributed to the growth o f the main crater on the active cone.