Masaya is a caldera located in Masaya, Nicaragua. It is Nicaragua’s first and largest national park. The complex volcano is composed of a nested set of calderas and craters, the largest of which is Las Sierras shield volcano and caldera. The vent is a shield type composing of basaltic lavas and tephras and includes a summit crater. Masaya continually emits large amounts of sulfur dioxide gas and volcanologists study this to better understand the behavior of the volcano and also evaluate the impact of acid rain and the potential for health problems.