Report on Masaya (Nicaragua) — December 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 12 (December 1980)
Managing Editor: David Squires.
Masaya (Nicaragua) Continued emission of a large gas plume
Please cite this report as:
Global Volcanism Program, 1980. Report on Masaya (Nicaragua). In: Squires, D. (ed.), Scientific Event Alert Network Bulletin, 5:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198012-344100.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
Emission of a very large gas plume has continued without interruption since fall, 1979. Remote sensing of SO2 revealed continued high level flux, with a 1,500-2,000 t/d average for the entire year. The hole through the surface of the lava lake was larger than in previous years and a great deal of sublimation was occurring around its edge. No lava or red glow was visible during daylight. Acid gas and rain continued to cause considerable damage downwind.
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: R. Stoiber, S. Williams, H. R. Naslund, L. Malinconico, and M. Conrad, Dartmouth College; A. Aburto Q., D. Fajardo B., Instituto de Investigaciones Sísmicas.