Report on Masaya (Nicaragua) — May 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 5 (May 1985)
Managing Editor: Lindsay McClelland.
Masaya (Nicaragua) Small ash eruptions
Please cite this report as:
Global Volcanism Program, 1985. Report on Masaya (Nicaragua) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198505-344100
11.985°N, 86.165°W; summit elev. 594 m
All times are local (unless otherwise noted)
In December 1983, 4,993 microearthquakes were recorded at Masaya. Early that month, a very large gas column was continuing to emerge from Santiago Crater. A series of small ash eruptions occurred in April 1984. There was a small gas explosion on 23 January 1985, and another ash eruption occurred in April 1985.
Geological Summary. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.
Information Contacts: D. Fajardo B., INETER.