Report on Masaya (Nicaragua) — July 1994
Bulletin of the Global Volcanism Network, vol. 19, no. 7 (July 1994)
Managing Editor: Richard Wunderman.
Masaya (Nicaragua) Sulfur-rich plume and incandescent ejections from opening in lava lake
Please cite this report as:
Global Volcanism Program, 1994. Report on Masaya (Nicaragua). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 19:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199407-344100.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
Scientists from FIU and INETER visited Masaya for about an hour on the afternoon of 26 May 1994 and noted that the two incandescent openings (5-7 m in diameter) in the cooling lava lake observed on 1 March near the N wall of Santiago crater (BGVN 19:03) had coalesced into a single opening 10-12 m long. A sulfur-rich plume was being emitted from the opening at a rate of several pulses/minute; the pulses were accompanied by jetting sounds easily heard from the S rim. Fresh, black ash covered the crater floor immediately SW of the opening. INETER scientists reported that small Strombolian explosions ejected incandescent material from the opening several times during May and June 1994.
Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is 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 twin volcanoes of Nindirí and Masaya, 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 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. 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 cause health hazards and crop damage.
Information Contacts: Peter C. La Femina, Michael Conway, and Andrew MacFarlane, FIU; Christian Lugo, INETER.