General features at Masaya Caldera. Main pyroclastic cones are numbered.



Masaya is the most active volcano in the region. The Spanish first described the volcano in 1524. Since then, Masaya has erupted at least 19 times. From 1965 to 1979 Masaya contained an active lava lake. The most recent eruption was in 1993. Masaya is an unusual basaltic volcano because it has had explosive eruptions. The eruption in 4550 B.C. was one of the largest on Earth in the last 10,000 years.


Summit of Masaya cone. Photography copyrighted by Robert Decker, May 1963.


Masaya is a caldera (4 by 7 miles, 6 by 11.5 km) that contains 13 vents. Most activity at these vents consisted of effusion of basaltic lava. Pyroclastic eruptions have constructed three main cones: Masaya, Nindiri, and Santiago. Santiago formed in 1850-1853. Spatter and scoria deposits indicate fire fountaining at Masaya, the only know occurrence of this type of eruption in Central America (Williams, 1981).

Unlike the stratovolcanoes that characterize subduction zones, Masaya has a shield-like morphology.

At times, Masaya emits large amounts of sulfur dioxide gas. In 1981, sulfur dioxide was released from Santiago Crater at a rate of 500,000 tons per year. Three periods of similar gas activity occurred this century. Volcanologists studied these events to better understand the impact of acid rain and the potential for health problems.

In 1979, Masaya became Nicaragua's first National Park (Parque Nacional Volcan Masaya).

Additional photos of Masaya are on the Electronic Volcano homepage.


October 7, 2003

On Oct. 4 an eruption cloud was reported at Masaya. The plume rose to a height of ~4.6 km a.s.l and was mainly composed of gas and steam.


This information was summarized from the GVP/USGS Weekly Volcanic Activity Report

24 April 2001

On 23 April, the crater Santiago of the Masaya volcano exploded and formed a new vent in the bottom of the crater. The explosion sent rocks with diameters up to 60 cm which travelled up to 500 m from the crater. Vehicles in the visitors area were damanged and one person was injured. In the later phases of the explosion, small quanities of lava and ash were released. During the night, there were several smaller explosions, gas outbreaks, and minor collapses of the crater wall. The National Park of Masaya Volcan has now closed the visitors area.

This information was summarized from the GVP/USGS Weekly Volcanic Activity Report

3 December 1999

On 22 November, the Masaya Volcano appears to have begun a new eruptive event. A hot spot has appeared on satellite imagery, and there was a possible explosion.

This information was summarized from the Global Volcanism Program.



Sources of Information:

Baxter, P.J., Stoiber, R.E., and Williams, S.N., 1982, Volcanic gases and health: Lancet, p. 150-151.

Decker, R., and Decker, B., 1989, Volcanoes: W.H. Freeman, New York, 285 p.

Johnson, N.M., and Parnell, R.A., Jr., 1986, Composition and distribution and neutralization of acid rain from Masaya volcano, Nicaragua: Tellas, in press.

Parnell, R.A., Jr., 1986, Processes of soil acidification in tropical durandepts, Nicaragua: Soil Science, in press.

Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.

Stoiber, R.E., and Williams, S.N., 1986, Sulfur and halogen gases at Masaya caldera complex, Nicaragua: Total flux and variations with time: Journal of Geophysical Research, v. 91, p. 12,215-12,231.

Williams, S.N., 1983, Plinian airfall of basaltic composition: Geology, v. 11, p. 211-214.

Williams, S.N., 1981, Masaya volcano, Nicaragua: IAVCEI Symposium, p. 416.

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