Latitude: 13.813 N
Longitude: 89.633 W
Elevation: 1950 m.a.s.l.
The above image is a LANDSAT image (1986) of bands 2,3 and 4. Izalco volcano can be seen as the grey to black structure. The lava flow at the right of Izalco is from the 1722 eruption of San Marcelino volcano. Izalco is a parasitic cone that is 4 km south and seaward from Santa Ana volcano's central crater (Carr and Pontier, 1981) and is part of the Central American volcanic chain This chain is a result of the convergence of the Cocos and the Caribbean plates. Carr et al. (1982) note that "the volcanic front is divided into eight segments, separated by zones of transverse faulting and offsets and changes in strike and dip of the seismic zone. The active volcanoes, most of which are probably younger than 100ka, were preceded by an earlier Quaternary volcanic front, and by several pulses of volcanic activity during the Tertiary.
The active volcanoes are clearly related to contemporaneous seismic activity. Great shallow thrust earthquakes are preceded by lulls in volcanic activity and followed by periods of intense volcanic activity. The most active volcanoes overlie portions of the inclined seismic zone that are largely aseismic, but there are concentrations of seismic activity at intermediate depths located just updip from these aseismic regions. This suggests strongly that magma is produced near the top of the descending slab."
The image below is from "Los Volcanes Activos de Guatemala y El Salvador" written by H. Meyer-Abich.
The image below is taken from "Los Volcanes Activos de Guatemala y El Salvador" written by Helmut Meyer-Abich in 1956, as shown in a geologic map of Lake Coatepeque which includes Santa Ana and Izalco volcanoes.