Zacate Grande volcano forms a low island 7 x 10 km wide across a narrow strait from the end of a peninsula surrounded on three sides by the Gulf of Fonseca and Chismuyo bay. At least seven satellitic cones, some of which form small islands offshore, are located from the NE to SE base of the broad basaltic stratovolcano. Some of these, including the symmetrical cone of Isla Gueguensi in the tidal flats about 3 km E of the base of Zacate Grande, are of probable Holocene age (Carr 1992, pers. comm.). In contrast to neighboring Isla El Tigre volcano to the S, Zacate Grande itself is extensively eroded, and deep valleys extend from the summit ridges to the base of the volcano.