The Escuintla and La Democracia debris avalanches are the two largest debris avalanches so far identified in Guatemala, with respective volumes of 9–15 km 3 and 2.4–5 km 3 . Based upon their geographic locations on the Guatemalan coastal plain, both deposits have several possible source volcanoes. The Escuintla debris avalanche could have originated at either the Fuego or Acatenango volcanic complexes, or Agua volcano. Farther to the west, the La Democracia debris avalanche could only have come from the Fuego or Acatenango volcanic complexes. An apparent collapse scar on the east face of the Meseta edifice (the northernmost vent of the Fuego volcanic complex) has been attributed to the formation of the Escuintla debris avalanche. A mostly obscured summit collapse scar on Acatenango and an erosional remnant of a debris avalanche deposit near the base of the cone have been linked to the La Democracia debris avalanche. Petrographic and geochemical analyses of lava blocks collected from the Escuintla debris avalanche suggest that a substantial volume of amphibole-bearing dacitic lavas were present at its source volcano. Examination of rocks from the possible source volcanoes indicate that no dacitic lavas or tephras are known to have erupted from the Fuego volcanic complex and that the rocks exposed in the Meseta scarp bear little resemblance to the Escuintla debris avalanche samples. A few dacitic lavas and tephras are known from the Agua volcano, and several dacitic tephras have erupted from Acatenango. Geochemical comparisons of lavas and tephras from these volcanoes with rocks from the Escuintla debris avalanche showed greater similarities than those from Fuego and Meseta. Even though Acatenango is not known to have erupted dacitic lavas, its geochemistry is the most consistent with that of the Escuintla debris avalanche. Lava blocks from the La Democracia debris avalanche are mostly basaltic, although one andesitic sample contains phenocrystic amphibole. Geochemical analyses of Fuego and Meseta lavas overlap with the La Democracia debris avalanche samples; however, no amphibole-bearing rocks are known from Meseta, and Fuego is presumed to be younger than the La Democracia debris avalanche. Compared to the Acatenango rocks, the geochemistry and mineralogy of the La Democracia debris avalanche are quite similar. Furthermore, rocks from the debris avalanche deposit on the flank of Acatenango are also consistent with the chemistry of the La Democracia debris avalanche. Thus, Acatenango produced at least one debris avalanche, the La Democracia debris avalanche, and possibly also generated the Escuintla debris avalanche.

San Miguel volcano in eastern El Salvador is a classic composite cone, symmetrical and concave upwards. Its summit crater exceeds 344 m in depth and consists of several nested craters with nearly vertical walls. The inner crater has grown in depth and size since it was first described in 1924. The dominant eruptive product at San Miguel has been lava flows. Spatter and scoria cones commonly occur at flank vents that erupted historic lava flows. Lava flows erupted from flank vents on several occasions between 1699 and 1867, traveling as far as 8 km from their vents. During this time interval, the elevation of flank vents increased. All subsequent activity has been minor Strombolian and ash eruptions in the summit crater. Occasionally, scoria fall deposits, pyroclastic flow deposits, and phreatomagmatic ashes have been produced, but no substantial explosive event has been positively linked to San Miguel. Few lahar deposits have been identified as a result of the preponderance of lavas exposed on the upper and middle slopes. Geochemical analyses of lavas, tephras, and block and ash flow deposits erupted from San Miguel indicate that the majority of activity has been mafic in character, ranging between 51 and 53 wt% SiO 2 . Historic flank lavas plot at the mafic end of the chemical range and are basaltic. The most evolved flank lavas are basaltic andesites and comprise two chemically distinct subsets, distinguished mostly by the presence or absence of phenocrystic magnetite and their V and Al 2 O 3 contents. They occur only on the eastern flank of the volcano and appear to represent some of the oldest exposed lavas. A stratigraphic sequence of 22 crater lavas has the most restricted compositional range and exhibits two chemical trends. These trends may represent rapid-fire eruptions, with little to no intervening reposes, from two distinct batches of magma. Overall, the development of San Miguel volcano is fairly simple and consists of two evolutionary stages. The first stage consisted of eruption of lavas from a central vent and growth of the symmetrical cone. Shallowing of the subvolcanic magma chamber may have been associated with this stage. This was followed by a significant change in the subvolcanic plumbing system characterized by flank eruptions and onset of the second growth stage. Magma draining laterally from the magma chamber to the flank vents led to the collapse of the summit region. Modification of the summit crater is an active process that continues today.