Report on Masaya (Nicaragua) — July 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 7 (July 1980)
Managing Editor: David Squires.
Masaya (Nicaragua) Large plume; high SO2 output
Please cite this report as:
Global Volcanism Program, 1980. Report on Masaya (Nicaragua). In: Squires, D. (ed.), Scientific Event Alert Network Bulletin, 5:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198007-344100.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
Emission of a very large plume continued in June. Remote sensing of SO2 gas revealed high output rates. The gas plume allowed only brief glimpses of the small pit crater in which an active lava lake had been observed on many occasions since 1970. The lake was not seen during the brief clear moments, nor did a glow appear in photographs of the pit. The lake's characteristic roaring noise, if present, was masked by the sounds created by gas emission. There were no night observations at Masaya.
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 and S. Williams, Dartmouth College; M. Carr and J. Walker, Rutgers Univ.; A. Creusot, INETER.